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RHO
01-28-2007, 04:06 PM
When we got the engine running yesterday I noticed the water temp. gauge never showed a reading. I checked it yesterday and found no output current. Checked the gas gauge today and same thing, no voltage reading on the sending unit side of the gauge. Power is supplied to to the IGN side of each gauge and I verified this. Both these gauges had 5-6 Volt output readings when I made the final installation into the dash back in April. Nothing behind the dash has been altered since. These are Two-Terminal gauges. Much too cold in the garage today to continue troubleshooting. Both gauges are new from SI and as I said had signals in April. Ideas? Should be no need to do it, but maybe connect an external ground up to the gauges casing and see if that makes a difference? Any other conceivable culprits?

'55 Commander
'55 President

N8N
01-28-2007, 04:39 PM
RHO,

if you end up needing new gauges let me know. I picked up a cluster from a parted '55 Prez and the only one I actually need is the oil pressure gauge.

nate

--
55 Commander Starlight
http://home.comcast.net/~njnagel

ROADRACELARK
01-28-2007, 04:42 PM
RHO,
Make sure to check the "engine" ground strap beside the right front motor support. May be loose, dirty, broken, etc. This could easily have an effect on the temp. and fuel guage as well as other electrical components. After all this wire completes the ground circuit form the frame to the negative battery cable.;) Hope this helps. OBTW, if this happens to be a fiberglass dash panel (Hawk or Avanti) the alternate ground wire you described for each guage will be a big help.

Dan Miller
Atlanta, GA

[img=left]http://static.flickr.com/57/228744729_7aff5f0118_m.jpg[/img=left]
Road Racers turn left AND right.

RHO
01-28-2007, 05:38 PM
Thanks. Hopefully this is some sort of wiring related problem as this is the second new gas gauge and of course the temp. gage is new. I will check that engine ground cable but I installed a brand new one....it isn't the old wire braided type but a big 0 gage cable even bigger than the battery cable. Previously with the gauge cluster checks in April, this cable was not installed. I am trying to think of a common denominator here for these two gauges and given both have power at the input side, grounding is all I came up with. Now I ponder if the addition of the engine ground cable somehow has caused this....don't see how, but that IS another commonality.

'55 Commander
'55 President

RHO
01-28-2007, 05:39 PM
Nate, thanks. I added an add-on oil pressure gage because I couldn't readily find an adapter to fit from the oil line to the back of that gauge.

'55 Commander
'55 President

RHO
01-29-2007, 04:25 PM
Well, this is a little bizarre. I switched from a 6-volt test bulb to a voltmeter and got readings: 5.4 Volts on the water temp. gauge output and 5.8 Volts on the gas gauge output. No discernible voltage drop on the gas gauge sending unit even at the lead at the back of the car. Perhaps the gauges are designed that way. I just don't understand why the test light (used three different ones) wouldn't show even a dim illumination. Then perhaps 10 minutes idling in the garage wasn't enought to bring the water temp. gauge up to any kind of reading. My '55 Commander is very very slow to read but I just attritbuted that to an old sending unit and gauge. Guess I will know next longer fireup of the engine. If the needle should be stuck, that might be hard to remedy.

'55 Commander
'55 President

motive
01-29-2007, 06:34 PM
Don't know if a Positive Ground system is the cause of your gauge problem. Could the gauges be reading "down" instead of up due to the reverse direction of current flow? Since the gauges are really only reading voltage, could one switch the input and output terminals and have the gauge read in "reverse" (read "positive" voltage instead of "negative" voltage? Does this make any sense to anyone, 'cause I'm just speculating.

Mike with Speedster

RHO
01-29-2007, 07:06 PM
This IS a positive ground system and before we started the car I polarized the Generator and while this took three or four iterations, I do have a charging generator. The gauges on the back are all marked with IGN and then whatever the other side is marked which I cannot remember. And this evening when I checked the output terminals of both gauges, I confirmed the positive ground was there because I had to reverse the terminals on the voltmeter.

'55 Commander
'55 President