PDA

View Full Version : Tachometer problem



MagikDraggin
03-11-2007, 02:43 PM
The tachometer in the '62 Hawk I have will sometimes read 2200 rpm at 65mph....sometimes it will read 2650 rpm at 65 mph...and today it only felt like registering 1950 rpm at 65 mph. Sometimes all I have to do is shut the motor off and come back in 5 or 10 minutes, take off again, and it will read something entirely different than it was reading previously. The needle is steady and does not jump around or waver.

What gives with this thing...what could be the cause and what would be the potential remedy?

Any ideas?

Karl

http://img.photobucket.com/albums/v147/MagikDraggin/Other%20Stuff/62StudebakerGTHawk1-small.jpg
1962 GT Hawk 4sp

JDP
03-11-2007, 02:47 PM
More then likely, it's a sticking tach that's dried out of lube.

64 Commander 2 dr.
64 Daytona HT
63 Cruiser
63 R2 4 speed GT Hawk (Black)
63 Avanti R1
63 Daytona convert
63 Lark 2 door
63 Lark 2 door #2
62 Daytona HT/ 4 speed
62 Lark 2 door
60 Lark HT
60 Hawk
59 3E truck
52 Starliner
51 Commander

MagikDraggin
03-11-2007, 02:57 PM
quote:Originally posted by JDP

More then likely, it's a sticking tach that's dried out of lube.


Ok, let's run with that idea. What would I need to do (my repair manual still has not shown up, so I have to "hoof" this alone and in the dark), to unstick the tach and what sort of lube should I use in the process?

Also keep in mind that when cruising at 65 mph, when I push the clutch in and rev the motor up, the tach needle does respond accordingly.....albeit most likely inaccurately. So, it's not like it's simply "stuck" in the sense of being "frozen in position".

Thanks for your response.

Karl

http://img.photobucket.com/albums/v147/MagikDraggin/Other%20Stuff/62StudebakerGTHawk1-small.jpg
1962 GT Hawk 4sp

MagikDraggin
03-12-2007, 06:51 PM
I sure could use some additional expert advice here on this matter. I just got my service and repair manual and on the subject of the tachometer, all it talks about is the part(s) associated with the distributor.

It says nothing about the drive cable and the actual "head unit" itself in the dash. Is the irratic action of the tach something which I can address and take care of, or do I simply need a whole new (different) unit?

I hesitate getting too involved with this thing, not knowing anything about how it functions. Anyone who can offer some 'words of wisdom' would be most appreciated.

Karl

http://img.photobucket.com/albums/v147/MagikDraggin/Other%20Stuff/62StudebakerGTHawk1-small.jpg
1962 GT Hawk 4sp

starlightchamp
03-12-2007, 08:58 PM
I'm not an expert on Tachometers but had to replace the driver for same on my 63 Hawk. I will be
watching this thread for any expert advice cause mine hunts a bit. Two things.
1. be sure you have the meter cover grounded well
2. If your sender is a small rectangular box--there is a 1/8 " hole in the cover to adjust something.
I haven't fooled with the adjustment yet myself.

John Kirchhoff
03-12-2007, 09:18 PM
Those were electric tachs and didn't use a speedometer type drive cable. I believe the GT tachs are pretty much the same as the 55 Speedster tach except for the voltage. Instead of using a cable turning a magnet to drag the needle along, it uses a synchronous electric motor which is powered by the electrical pulses sent to it by the sender on the distributor. I think first I'd check the brushes on the sending unit. Iv'e never had my hands on one, so I'm just going by how they work. I'd see if the commutator it dirty or possibably oily. I don't know it I'd use brake cleaner to clean things because that's some pretty stout stuff and it doesn't like some plastics. Starting fluid without "upper cylinder lubricant" (light oil) is good for removing oil and it then evaporates away leaving thing high and dry. You might see if the brushes are in firm contact with the commutator. If they aren't, that could give erratic readings. If that doesn't do any good, you might then remove the tach. On the back you should be able to remove two small (5/16"?) nuts and the rear half of the motor shell can be slipped back while you thread it over the cable. You'll find four little brushes located 90 degrees to each other. If you look down between these, you will see the rear bushing the motor shaft rides on. You might take a little WD-40 and lubricate the bushing and see if that helps. Take a look at the commutator surface the brushes ride on and it should look fairly clean and copper colored. If it looks dirty or kind of burned, it will probably need to be cleaned and the brushes might be worn. I haven't torn one apart completely, so at first I'd just try lubing the rear bushing. If that doesn't help, I have a Speedster tach in the shed I can try to pull apart to give you better instructions on going further. Oh, you might make sure the electrical connections of the three prong plug are clean and any other connections on the sender. To me it sounds like either the tach motor shaft needs lubing or it's getting erratic signals delivered to it. Everything I've described so far is pretty simple and just about anyone could do it, so don't fret about it.

GTtim
03-12-2007, 09:40 PM
The GT tachs are early electric tachs and aren't all that accurate. The technology has improved a lot since then. I agree with Starlight, make sure there is a wire running directly from the case of the dial to a good ground like the brace at the bottom of the dash. This ground will solve a lot of tach problems.

Tim K.
'64 R2 GT Hawk

MagikDraggin
03-12-2007, 10:52 PM
quote:To me it sounds like either the tach motor shaft needs lubing or it's getting erratic signals delivered to it. Everything I've described so far is pretty simple and just about anyone could do it, so don't fret about it.


Oh but I do fret over such things, John. I feel like a person who is comfortable filleting a fish, being asked to perform open heart surgery.

Your explanation is very concise sounding....but me and my dummie mentality here, is not certain if all you are referring to is contained within what I would call the tachometer head (the gauge on the inst panel), or the components that drive the thing found inside the distributor.

Indulge me please, and walk me through this one more time, if you would. The manual states explicitly not to be lubing anything to do with the tach sending unit, so that further adds to my confusion here.

Anyway, if push ends up becoming shove and I need to focus my attention on the dash unit.....do I need to actually remove the unit from the instr panel? According to the instructions, that sounds like a real PITA job, taking the panel apart.

I know I could probably take the easy way out and buy an aftermarket Sun tach, but I'd really rather keep the stock one if at all possible.

http://img.photobucket.com/albums/v147/MagikDraggin/Other%20Stuff/62StudebakerGTHawk1-small.jpg
1962 GT Hawk 4sp

MagikDraggin
03-12-2007, 10:58 PM
quote:Originally posted by GTtim

The GT tachs are early electric tachs and aren't all that accurate. The technology has improved a lot since then. I agree with Starlight, make sure there is a wire running directly from the case of the dial to a good ground like the brace at the bottom of the dash. This ground will solve a lot of tach problems.

Tim K.
'64 R2 GT Hawk


I kinda gathered that, from reading the manual, Tim, but it doesn't ease my mind when it comes to messing with it. However, I definitely can check to insure it is grounded properly and that the rest of the wiring is in order.

This Hawk is in fine condition overall...just a few little things that need to be brought up to snuff that's giving me fits.

Thanks for the response and tips.

http://img.photobucket.com/albums/v147/MagikDraggin/Other%20Stuff/62StudebakerGTHawk1-small.jpg
1962 GT Hawk 4sp

JDP
03-12-2007, 11:16 PM
If you think getting it out of the dash is a PITA, wait until you remove the bezel to check the movemaent. It might be better to risk the $80 on a new sender first.

64 Commander 2 dr.
64 Daytona HT
63 Cruiser
63 R2 4 speed GT Hawk (Black)
63 Avanti R1
63 Daytona convert
63 Lark 2 door
63 Lark 2 door #2
62 Daytona HT/ 4 speed
62 Lark 2 door
60 Lark HT
60 Hawk
59 3E truck
52 Starliner
51 Commander

studebaker-R2-4-me
03-13-2007, 01:17 AM
I would agree with JP on this one. If you think it is difficult taking the tach out try fixing it once you get it out. You have to pry up the black retaining ring ever so carefully, clean everything (glass, dial face)lubicate, reassemble then hit the retaining ring back down again. Just when you think you have it back together..... you have to get it back into the chrome face ring only to discover it does not fit anymore! Try to do that with your newly purchased $250 USD Rare Redline Tach! Good luck if all else fails I have a perfectly working standard tach that I replaced with my redline tach that is sitting on my shelf.- Allen

http://i122.photobucket.com/albums/o278/studebaker-r2-4-me/1964.jpg

1964 GT Hawk soon to be R2 Clone

starlightchamp
03-13-2007, 01:27 PM
Hi Majik (Puff?)
Look at the post today on Clock/Tach and go to the address suggested by B. Shaw.
This will give you everything you need to know about how the tach works and how to trouble shoot. It is an EXCELLENT treatise albeit quite technical. Basically it shows how the points
opening and closing create a pulse rate that the sender uses to average out a current that energizes the magnetic coil and hence the ponter. It explains how to check out the Tach. head and the sender unit in great detail.
BTW did you check the case ground and adjust the rheostat through the hole in the sender unit ? Did it help ?

1950 Champion Starlight
1963 Hawk GT
Santa Barbara
CA
http://farm1.static.flickr.com/125/368321841_7d3a05da00_t.jpg
http://farm1.static.flickr.com/185/367175252_40e3cec1d9_t.jpg

Dwain G.
03-13-2007, 01:48 PM
quote:
.............or the components that drive the thing found inside the distributor.

No tachometer components inside the distributor, that was a different system used on 1961 and earlier.

http://home.comcast.net/~jdwain/63.63.jpg
Dwain G.

John Kirchhoff
03-13-2007, 01:52 PM
The manual says not to lube the sending unit on the distributor because any oil that gets between the brushes (the square or rectangular graphite things that ride on the commutator) and the commutator (the segmented part of the shaft they ride on)will cause a bad connection. Something like some points cleaner or starting fluid would clean off any carbon dust without leaving an oily residue. I believe that's the first thing I'd do. While you're at it, take something like a toothpick or sharpened pencil (not sure of how much room to work) and slip the point between the commutator and the brush (don't worry, you won't hurt anything) and push the brush away from the commutator. The brush is spring loaded and should provide resistance from the get go. If the brush seems to lack firm pressure against the commutator, it is probably worn. Most brushes I've seen regardless of the application tend to be around twice as long as they are wide. When they get "square", the spring pressure is usually too little to make good connection. Like I said, I've never had my grimy mitts on a sending unit, but I'd expect the brush to have a braided copper wire attached to it coming out the side or end of the brush holder. The little coil spring behind it is most likely not restrained in any way. So if you remove the whole unit or take things apart, be careful that the spring doesn't jump out. If the brush seems too short and/or the spring pressure too little, you might be able to fashion a little spacer to place behind the spring opposite of the brush end. Whittle a little piece of wood, cardboard or the like about the thickness of the brush and that should increase the contact pressure of the brush. If things work better, then you know the brushes are worn but it'll probably run a long time that way. If you take the sending unit apart and have unfettered access to the commutator, then is the time to take some 400-600 sandpaper and clean it up if it looks dirty like an old penny that's been exposed to the weather. If it has the color of a penny you carry around in your pocket, don't worry.

Removing the tach in a 60 Hawk is a pain and I'm sure it is in a GT also. A couple of people mentioned possible grounding problems. You might get a piece of wire and affix a little alligator clamp to each end. One you can attach to the little nut on the back of the tach and the other to anything well grounded. That would be a good way to rule that out without going to all the hassle of removing it. I'd probably focus first on the ground and then the sending unit since it's exposed to heat, oil fumes and other elements. If things still act up, then it might be time to check out the tach itself. As I said earlier, I'd look at lubricating the rear bearing on the tach motor. It's easy to get to and my experience with all sorts of electric motors seems that more often than not it's the brush end bearing that's the driest. Id try something like WD-40 first to cut any dried grease and maybe then add just a drop or so of oil. I'll have to look closer at my tach to see how it comes apart when going further.

Hopefully it wouldn't be necessary to remove the bezel because I agree, it is a pain. If worse comes to worse and you do, try taking a nail with a head that's a little wider than the distance between the tach case and the lip of the bezel and file one side of the head down to kind of a sharp edge. Bending the nail may give you a better handhold. With this you should be able to use the sharp edge to get under the backside of the bezel and pry up just a bit. Move over and repeat and go around and around like you were opening up a can can of paint. Pry the edge up just far enough to slip it off over the front. For putting it back on, put th ebezel in place and place the tach face down on something solid like a table with a wash cloth (prevent scratching) and push down firmly, applying pressure to the bezel on the bottom. Take a piece of wooden dowl or your wife's wooden cook spoon and bend back a little spot, not all the way but j

JDP
03-13-2007, 01:56 PM
Wrong year Hawk John, the 62 Hawk is all electronic with a solid state sender.

64 Commander 2 dr.
64 GT Hawk R2 clone
64 Daytona HT
63 Cruiser
63 R2 4 speed GT Hawk (Black)
63 Avanti R1
63 Daytona convert
63 Lark 2 door
63 Lark 2 door #2
62 Daytona HT/ 4 speed
62 Lark 2 door
60 Lark HT
60 Hawk
59 3E truck
52 Starliner
51 Commander

John Kirchhoff
03-13-2007, 02:15 PM
Thanks JDP, then that rules out the sender since it operates off the Hall Effect just like an electronic ignition. I have several elecronic tachs in the shop, I'll have to tear into the indicator unit and see what moves and what doesn't move.

John Kirchhoff
03-16-2007, 10:42 PM
I tore apart an electric tach tonight. It wasn't a Stude job, but chances are they're are much alike. Karl, if you're intent on checking things out and you're down to the tach, you'll most likely have to remove the bezel like I described earlier. Take a look and see if the faceplate has a screw or two on it and if there's also one or two on the back side of the housing. On the one I have, there was one screw holding the faceplate and two on the rear which hold the guts in. Remove the screws front and rear and everything should come out the front of the case. On mine the little indicator unit had a plastic cover front and rear and after removing them, I had access to the tiny shaft with a clock type spring on both ends that ride on jeweled bearings. Very reminisicant of the insides of a mechanical auto clock. If any lubing of the bearings need to be done, I'd probably look at something light like WD 40 rather than oil.

Before you tear things apart though, you might want to remove the tach from the dash and while holding it in your hand with the face toward you, rotate it clockwise sharply. This twisting movement should cause the needle to rotate to the right and if it wants to hang up anywhere, it should be evident. I've done this before and if nothing is dragging, the needle will return to its resting position smoothly and evenly. Use big twists to get the needle to go all the way over but also use smaller ones to get the needle to only go part of the way. I had one tach that would return all the way home when cranked over to 8k, but when cranked to the 4k mark, it would hang up at around 3k. If yours returns smoothly, I don't think anything would be gained by tearing it apart.

MagikDraggin
03-16-2007, 11:08 PM
quote:Originally posted by John Kirchhoff

I tore apart an electric tach tonight. It wasn't a Stude job, but chances are they're are much alike. Karl, if you're intent on checking things out and you're down to the tach, you'll most likely have to remove the bezel like I described earlier.


Man, I dunno, John. The thing does work, just not consistently. It never "sticks" or even acts "sticky". When I blip the throttle, it responds quickly and efficiently. It's just when cruising at highway speeds, say 60 mph just for example, one time it will indicate 1900 rpm. The next time it might indicate something like 2200 rpm.

From what I've been reading so far on this subject, it seems likely I run a high risk of ending up with a non-functioning tach, or at the worst, a place in the instrument panel where the tach used to be because I couldn't get the thing back together again.

I don't really "need" the thing....I just figured it'd be nice if it could be made to be a bit more accurate/consistent. Knowing me and my kinda luck, after I got done messing with it, it won't work at all, and then that would really tick me off, heh, heh, heh.

I appreciate your and everybody elses input.....yes, I am copping out here....call me a wus, chicken, or whatever. I just ain't that gutsy. Now, if like you, I had a spare sitting around, I'd love to take it apart and see what makes it "tick".

Karl

http://img.photobucket.com/albums/v147/MagikDraggin/Other%20Stuff/62StudebakerGTHawk1-small.jpg
1962 GT Hawk 4sp

JDP
03-17-2007, 12:13 AM
You don't by chance have a electronic voltage regulator conversion ?

64 Commander 2 dr.
64 GT Hawk R2 clone
64 Daytona HT
63 Cruiser
63 R2 4 speed GT Hawk (Black)
63 Avanti R1
63 Daytona convert
63 Lark 2 door
63 Lark 2 door #2
62 Daytona HT/ 4 speed
62 Lark 2 door
60 Lark HT
60 Hawk
59 3E truck
52 Starliner
51 Commander

StudeRich
03-17-2007, 12:43 AM
I think that possibly a problem in that "not known to be dependable" Prestolite distributor, like a bare or loose wire, bad points, problem with centrifugal advance weights could cause a inconsistent Tach. reading since that is where it's signal comes from. [:0]

StudeRich
Studebakers Northwest
Ferndale, WA

MagikDraggin
03-17-2007, 11:58 AM
quote:Originally posted by JDP

You don't by chance have a electronic voltage regulator conversion ?


Nope, but thanks for asking.

Karl

http://img.photobucket.com/albums/v147/MagikDraggin/Other%20Stuff/62StudebakerGTHawk1-small.jpg
1962 GT Hawk 4sp

MagikDraggin
03-17-2007, 12:10 PM
quote:Originally posted by StudeRich

I think that possibly a problem in that "not known to be dependable" Prestolite distributor, like a bare or loose wire, bad points, problem with centrifugal advance weights could cause a inconsistent Tach. reading since that is where it's signal comes from. [:0]

StudeRich
Studebakers Northwest
Ferndale, WA


Well, I notice that the dist cap appears to be brand new. I don't know what the PO may or may not have done inside....so, I guess it's time I broke out the dwell meter and check all the stuff that could go wrong with the innards.

Man, I haven't checked on distributor points and such for what now, 40 years? Has it really been that long? Man, how time flies when you're "having fun", heh, heh, heh.

Like I mentioned to John, if it isn't something readily obvious, I'm not going to be spending a whole lotta time troubleshooting this particular problem. It's not like I'm going to be rapping this old 289 up to 5 grand any time soon and need an accurate reading. I just intend on 'driving' this Hawk, not racing it.

Karl

http://img.photobucket.com/albums/v147/MagikDraggin/Other%20Stuff/62StudebakerGTHawk1-small.jpg
1962 GT Hawk 4sp

starlightchamp
03-17-2007, 12:53 PM
According to the article referenced above by B. Shaw, the 62-64 Tachs use the back EMF
of the coils primary winding, about 200 volts, pulsed at the rate of point open and closing. to give the sender unit a stream of pulses. The amplitude of these pulses is not a factor
since it is the pulse rate that is read and averaged through a transformer in the sender unit that then tranfers current to the Tachometer magnectic field coils.
The Tach gauge has a selinium diode rectifier internally that can be checked by connecting a 1 1/2 volt battery across the terminals,one with a white wire,the other a yellow wire. With the battery connected , you should read either 0 rpm or 2000 rpm depending on the polarity of the connection. If the needle goes negative ,you have a bad selinium rectifier and the gauge will need repairing. A better check, if you have an OHMETER is to check the resistance,using the x1 scale. The low resistance reading should have the needle read between 1600 and 1900. The author points out that the selinium rectifier is a non-linear device and is the primary error inducer at high speeds. Selinium, IMHO, is no longer used since silicon or germanium diodes have replaced them since the early 60's. I belieive the wander in my Tach may be due to a this rectifier no longer in its prime. You might call Bob's Speedometer Service,800-592-9673 to get an idea of repair costs. It sure looks pretty in the dash and should be kept working.
BTW this article has diagrams of the whole system and is well presented.
Good Luck
Dick Curtis

Swifster
03-17-2007, 01:02 PM
quote:Originally posted by MagikDraggin

It's not like I'm going to be rapping this old 289 up to 5 grand any time soon and need an accurate reading. I just intend on 'driving' this Hawk, not racing it.

Karl, you say that now, but one nice Sunday morning you'll have the 'ol girl out for some exercise and...BAM

http://i74.photobucket.com/albums/i280/Swifster/redlight.jpg

You'll have some punk 'kid' in his '63 Rambler Ambassador telling you what an 'old persons' car your driving while waiting for the next light. And dam it, no one talks about your Hawk like that!

http://i74.photobucket.com/albums/i280/Swifster/greenlight.jpg

Just make sure that tach reads right.

http://i74.photobucket.com/albums/i280/Swifster/HawkDash.jpg

HEY! It could happen [8D].

---------------------------------------------------------------------------------------------------
Tom - Valrico, FL

1964 Studebaker Daytona

http://i74.photobucket.com/albums/i280/Swifster/1965_Studebaker_Commander_front198x.jpg

John Kirchhoff
03-17-2007, 01:12 PM
Karl, I don't consider you a wus, I consider you to be pretty smart for knowing when to quit. There's been too many times when I thought I was going to do a little preventative maintenace on something and ended up twisting off bolts corroded into aluminum, barfing up gaskets and so on. Those are the times when I wished I was as cautious and smart as you because it would have saved me a LOT of extra work. And cussing.

Since the tach works and isn't really vital to the car's operation, I think I'd just make sure any wire connections are clean and maybe do the wire-alligator clip trick to make sure the ground is sufficient. Since the sender is solid state, I might ask if heat or ttemperature seems to make any difference, cool, hot or really hot engine, long runs verses short runs and such. Being solid state, that means there are no moving parts, just magnetic pickups (also called pulse generators or Hall sensors) which operate just like a pointless electronic ignition. Inside the pickup are little tiny windings through which current is induced. When the insulating material begins to break down, they stop doing what they're supposed to be doing. Often times, they do this initially when they get heated up from engine heat but work fine when cold. On ignitions, I've had them work intermitently at random times before failing completely while others just konk out without warning. That's why I carry an extra set on my motorcycle. From the diagram I saw, I believe your sender has three pickups. If one is starting to go bad, that could explain the odd readings at times since when one starts shorting out internally, it's creating fewer pulses for the tach to detect.

If you ever get curious, you might take a look at the sender. There should be an air space between the pickup and the sharp peak on the rotor. Normally .010" is the proper distance, but if you check it, be sure to use a brass feeler gauge and not steel. Many gauges anymore have both a steel and brass .010" just for that reason. If the distance is too wide, you won't get a pulse from that pickup. I've never seen one first hand, but I'm guessing that if the distributor bushings are getting loose, the distance between the pickups may vary just enough to cause intermittent or uneven pulsing.

Oh well, if you never check further that's fine with me. It's just that I hate leaving those kinds of problems unanswered. You know, kind of like "Me man, you machine, me boss!" However, it might be just a bit of OCD..........

GTtim
03-17-2007, 01:21 PM
Karl, I have noticed when driving my Hawk that the tach reading will change if I; turn the heater blower to high or low, or if I turn on lights and wipers. I figure it is just part of the old electronics thing. I have also noticed that at least some of the drag racers use new tachs strapped to the steering column. I suggest you leave a little margin for error when you do your street racing.

Tim K.
'64 R2 GT Hawk

MagikDraggin
03-18-2007, 03:43 PM
quote:Originally posted by Swifster


quote:Originally posted by MagikDraggin

It's not like I'm going to be rapping this old 289 up to 5 grand any time soon and need an accurate reading. I just intend on 'driving' this Hawk, not racing it.

Karl, you say that now, but one nice Sunday morning you'll have the 'ol girl out for some exercise and...BAM

http://i74.photobucket.com/albums/i280/Swifster/redlight.jpg

You'll have some punk 'kid' in his '63 Rambler Ambassador telling you what an 'old persons' car your driving while waiting for the next light. And dam it, no one talks about your Hawk like that!

http://i74.photobucket.com/albums/i280/Swifster/greenlight.jpg

Just make sure that tach reads right.

http://i74.photobucket.com/albums/i280/Swifster/HawkDash.jpg

HEY! It could happen [8D].




Hahahaha, my luck I'd end up tangling with something like a riced-out Honda Accord, loaded down with "Nawz", and have my butt handed to me by some kid that is still trying to grasp the basic fundamentals of chewing gum and listening to rap music at the same time.

Don't wanna give the "old girl" a heart attack, ya know.http://img.photobucket.com/albums/v147/MagikDraggin/Other%20Stuff/smilielol51.gif

http://img.photobucket.com/albums/v147/MagikDraggin/Other%20Stuff/IM000985reduced.jpg1962 GT Hawk 4sp