The setup is this: 31 Model A with 351C. The gauges have been in the car 40 years. They are from a 60's Studebaker, about a 4" speedo, and a matching cluster gauge of ammeter, fuel, oil, and temp. I built a custom dash out of oak for the gauges. The car was "inactive" for about a decade. Now, the ammeter and the temp gauge don't work. The temp gauge will go to about 3/4 in a couple of minutes, and then all the way to hot in about 5-10 min. I used on OE type electrical sending unit that fit the Cleveland, and it was always pretty much in the middle of the gauge previously. (That, presumably, would eliminate any kind of voltage/resistance type of mismatch). I have added a stand alone mechanical temp gauge that never goes over 180*. The ammeter, which worked before, now only shows neutral or a slight discharge. Voltmeter shows that the alternator is charging, plus it's been like this for several months with no other problem. In a static situation, if I turn on the headlights, no movement; but I start the engine (or switch to "ON" with the electric fuel pump running) and it shows discharge by about an 1/8 of an inch (or a 1/4 of the capacity of the gauge). The oil pressure is analog, and works. The fuel gauge is not accurate, primarily because I had to replace the fuel tank and sender, and they weren't compatible. That's another project. Related to that, the speedo froze up; which ties it all together. I can actually buy a used Stude speedo for about half the price of a new aftermarket one; but if I can't get the other gauges to work, then why do it? I'm retired, so time is no object, but money is..... Any ideas on tracking this down ? Also, I use a 12 circuit Painless Box and ground seems good.
might look carefully at how the ammeter is wired...it should be between the battery and 'everything else". The temp gauge needs the matching sender for that gauge, not the sender that was designed for whatever engine you happen to have.
Sure, but the kicker is: it all worked before ! The only thing that has changed was the new fuel tank, and I know that is a mismatch. Nothing changes if I disconnect the fuel sending unit.
If it was installed 40 years ago, then sat for 10 years and everything worked perfectly the first 30 years...that means gauges, wiring, sending units, etc. are (or were) all ok. If I had to troubleshoot I'd start with what's easiest first, maybe removing instrument cluster? Especially since some aren't working correctly. Something may be obvious, bad connection(s), or ground. If gauges aren't hard to remove they could be checked individually. Ammeter (is it marked? Pictures would help.) You could test it out of cluster. A battery charger connected to a battery needing charge, say it's charging 10 amps...put meter in series with one lead, meter will show charge then flip around should show discharge same needle distance on ammeter. Another simple test with ammeter in cluster. Turn key on (engine not running)...turn lights, pump, horn and everything on, ammeter should show discharge a lot. Then key off. Temporarily reverse ammeter leads, then same process (key on, everything on)...ammeter should read charge needle moving same distance as before. If ammeter fails this test, it needs to be replaced. (A good ammeter will show discharge with load, charge with load if connected backwards). Temp gauge. As squirrel said sender has to match gauge not motor. If you could find specs for that Studebaker sender you could check it with an ohm meter. If you can replace that sending unit exactly that WAS working with a new one inexpensively I would try that. If meter still reads incorrectly replace it. Fuel sender is just a variable resistor (potentiometer) in tank with a float...like temp gauge it has to match fuel gauge to read correctly. Knowing what that Studebaker gauge sending unit specs and what's in the tank now specs would be helpful. Sent from my SM-S320VL using Tapatalk
Any car that's sat for ten years should probably have all wiring terminals cleaned up to remove corrosion. Buy one of those toothbrush sized stainless steel brushes from the cheap tool man at the next swap meet. Use it on all wiring connections to clean them up, then put a dab of dielectric grease on each before reassembly. Then tell us what works and what doesn't.
Like Alchemy said, check all your connections. Don't know where you're at, but in some climates metals corrode fast. Just a little invisible corrosion will make a joint that looks good totally inoperative. Just because two terminals are tight and touching doesn't mean they are making a connection, seen it many times.
I revived a British car a few years ago that had been sitting for a while. Much of the electrics didn’t work properly (famous on British cars). Scrubbing each connection clean made a world of difference.
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