To recap: 4 months ago, temp gauge was dead. I bypassed the temp. faker, and the gauge read 1/4 after car fully warmed up. I replaced the thermostat--still 1/4. Today, I put a 68-ohm resistor between sender wire and ground, expecting to condemn the sending unit. Nope! Gauge read only a needle's width above 1/2 instead of 3/4 per Bentley.

The voltage regulator seems to be fine (fuel gauge accurate and measured 9.8v out. So, can I condemn the gauge now, or am I still (potentially) missing something? I suppose I'll have to track down another gauge or cluster to be totally sure. From the archives, a gauge this far off seems rare. I don't suppose there;s any adjustment posisble?

It's my wife's car, so I'd rather red mean red. If it were mine, I'd probably just recalibrate my eyes.

Edit: I should probably mention that I know little about electricity. I just bought a 68 ohm resistor at Radio Shack and alligator clipped it between the sender wire and the body. I did try a couple of different ground points to make sure I had a decent one.

Best,
joe
portland, or
93 245 317k

Don't run with too low/cool of a thermostat. It will cause all sorts of problems later in life, like carboned up cylinder head and valves.. too cool is not good.

As for the gauge, unless I missed something, you verified the wiring and gauge is good with the 68 ohm resistor, but doing so you eliminated the actual sending unit itself by disconnecting it to attach the resistor! So it looks like the sending unit in the block is whacky! Did you replace the sending unit itself? There's nothing left.....

Newyankee
--
Genesis 7:11

An easy check of the voltage regulator is to look at both the fuel gauge and temperature gauge -- they're both dependent on that voltage regulator, so if the fuel gauge is working properly, the voltage regulator is not the problem.

You said that you changed the thermostat, but perhaps you installed the wrong temperature 'stat -- and that presumes that it was of good quality. There are three temperature versions: 87, 89 and 92 deg C.

I'd suspect that you installed the 87, which would (and should) keep the temperature gauge's needle low, instead of near the middle. The 89 will keep it nearer the needle (now that you wisely removed the TCB), and the 92 will keep it slightly above.
BTW, the 87 is really too cool for efficient fuel economy -- the 92 is best for that, if you're not in a hot climate.