M5 Dash Gauges

[samson009]

I recently bought a 1948 M5 pickup that has been modified using a 4.3 gm engine with automatic transmission, Mustang II front end with 9" ford rear end.
I have after market guages mounted under the dash.

I would like to get the origional gauges working. It was converted to 12 volt.

Can someone give some direction as to what can be done ?



jan
1948 M5
1951 Champion Starlite Coupe
1956 Powerhawk

[Dick Steinkamp]

quote:Originally posted by samson009


I recently bought a 1948 M5 pickup that has been modified using a 4.3 gm engine with automatic transmission, Mustang II front end with 9" ford rear end.
I have after market guages mounted under the dash.

I would like to get the origional gauges working. It was converted to 12 volt.

Can someone give some direction as to what can be done ?

Only the stock M5 gas gauge would need some help, and in that case, a 12 to 6 voltage drop available from Ron Francis http://www.wire-works.com/groundingandcharging.php (and probably other vendors) will do the trick. The water temp, oil pressure, and speedo are mechanical. The ammeter doesn't care how many volts it sees.

See Gary Ash's web page for a great step-by-step on restoring M5 gauges... http://www.studegarage.com/instruments.htm

-Dick-

[N8N]

I am basing my comments on having done this to a '55 coupe, not sure about M-series gauges other than I know that they are the same as some earlier passenger car ('41?) I am making some assumptions here...

Anyway, the ammeter will work fine as is, although you will have to reverse the connections because you've switched from positive to negative ground. I'm not sure how you're currently wired, but basically the output of the alternator should go from the alternator back to the ammeter through a large (8 ga. would be nice, and IIRC is the stock size) wire then back to the battery, wherever the connection to the large battery cable is. (I assume back of starter) you can pick off power for the rest of the vehicle from the alternator side of the ammeter. If you are using an alternator which puts out significantly more than 40-60 amps, you may want to rethink using the stock ammeter. I'd also recommend sticking with a "3-wire" alternator because you will possibly have a decent voltage drop through the long wire run described above. Speedway sells an adapter with a diode to use a 3-wire alternator without an idiot light. I am using one in my '55 and it works fine.

The oil pressure gauge should be mechanical, so no issues there. Just hook it up.

The water temperature gauge, I assume is electrical. If so, what you need to do is to get a stock sending unit for your year/model truck, and fit it to your engine. You may need to use a reducer bushing and/or enlarge a hole in one of the water passages. Then hook it up as stock, but you will need a voltage reducer to provide appx. 7V to the gauge. Speedway Motors (and others) sell what's called a "Runtz" which is a little transistorized voltage reducer which fits right on the terminal of the gauge. I used these on my '55 with no problems. Gauges work fine. The difference in polarity is not important here, the electrical gauges work off of the amount of current flowing through them. If the gauge is mechanical however just use it... (although if it is, the bourdon tube has probably been cut so you will need to find a new one.)

For the fuel gauge, procedure is exactly the same as for water temp. gauge above. We know this one is electrical

hope this helps

nate

--
55 Commander Starlight
62 Daytona hardtop

http://home.comcast.net/~njnagel

[Dick Steinkamp]

BTW, here's another idea. This from Jim King's beautiful 289 Stude powered M15 flat bed...



The gauges are from a mid 70's Ford pickup.

-Dick-

[garyash]

The radimeter (temp gauge) is a mechanical one, not electrical. It counts on the expansion of vapor in a small bulb as a function of temperature. You would need to have a place where the temp sensor bulb can be completely immersed in water in the head. It's probably not too practical. I think you would be better off getting any modern 12 volt electrical gauge and then re-cut and repaint the face to match the old M5 gauges. And, yes, I do have some decals that will help. Premium Decor brand decorative spray enamel PDS-16 Almond is a close match to the original color. It is sold by True Value hardware stores.

The M5 ammeter is only good for 30 amps. Your 12 volt alternator will easily do twice that. We hope you have a complete new wiring harness with heavy gauge wires, not the old skinny stuff with rotten insulation. Rather than an ammeter, you might just put in a voltmeter, then you don't need to run the heavy current all around. All you really care about is the relative position of the voltmeter needle to show that its keeping battery charge up, not the actual numbers on the dial face, though you could transfer the scales of whatever voltmeter you get. You can get a marking pen with gold ink at an art supply or large hobby supply store to make a couple of marks since I don't have voltmeter decals. [The gauges in older airplanes were always set so that the needle was straight up when things were good - you didn't have to read the values, just scan for any needle out of position.] The gas gauge, as mentioned, needs the dropping resistor and oil gauge is mechanical.

Gary Ash
Dartmouth, MA
'48 M5
'65 Wagonaire Commander
'63 Wagonaire Standard

https://www.studegarage.com

[Dick Steinkamp]

quote:Originally posted by garyash



The M5 ammeter is only good for 30 amps. Your 12 volt alternator will easily do twice that.

I've got a Delco internally regulated 60 amp alternator on my '54 with the stock ammeter. I have not seen the ammeter go to more than half scale. My car isn't very complex electrically (no power windows, air, etc.). I guess it's possible that the alternator will want to put out 60 amps at some point in time, but I wonder under what conditions this would happen?

-Dick-

[DilloCrafter]

Some great information here in this thread, gentlemen.

Rather than start a new thread, I hope you don't mind if I jump in with a 1955 truck question about gauges. The truck was converted to 12v by the previous owner, but he left the ammeter and fuel gauge disconnected. I replaced the old 6v fuel gauge with a NOS 12v version like they began using in 1956 (but have not connected it yet, as the gauge cluster is out of the truck at the moment for restoration).

QUESTION: Will I need a later model fuel sending unit for the gas tank to go along with the 12v gauge, since more voltage will now be applied? Or can I keep the original sending unit (I don't know the voltage rating on it, but the resistance measures from approx. 0-100 ohms).

Finally, I couldn't help but show off my gauge cluster after all the repainting I did to the gauge dials, needles and gauge panel this past weekend. It's not complete yet, but notice the icons I designed for each of the gauges. Since the panel was rusted, it had to be repainted anyway, which was going to obliterate the original white ring around each gauge location and the not-so-attractive cross hatch design beneath each gauge. I drew icons for "charging", "gas", "oil" and "temperature" that look like they might have been designed to look in 1955 if they had used icons on the gauges back then. These are simply mockups I printed and cut out, but I am working on doing it with the white letter decal kit I got from www.supercaldecals.com.



1955 1/2 Ton Pickup

[Dick Steinkamp]

quote:Originally posted by DilloCrafter



Finally, I couldn't help but show off my gauge cluster after all the repainting I did to the gauge dials, needles and gauge panel this past weekend.

Very nice! Tx for posting the pic.

-Dick-