oakley_77

Hey Guys/Girls,

I have an issue with my temperature gauge on my 72 coupe. It quit working on me over the winter and I've spent many hours trying to fix it ever since. It still won't read anything above 110-120 degrees.

I've tried 4 different temperature senders (the one that was working last year, the original from the base 350 motor, one from AC delco and one from Standard). I've also tried 2 different gauges.

I tested the the power and ground in the back of the gauge and they seems fine. I also ran another wire from the sender to the gauge and it still the same result. (nothing over 120)

Here is the tricky part. We setup the gauge on my work bench with a battery charger and tried it with one of the 4 sender and the needele moves!

I am pretty sure the temp sender is doing its job since put a multimeter to it yesterday and it read 175 ohms at 150 degrees...


Did anyboby out there have this issue before? I have had 3 mechanics take a look at this issue but no luck yet...Any information would be appreciated.

...Roger...

Is the resistor across the back good ?

oakley_77

Yes, the resistor seems to be good. I've tried 2 of them.

oakley_77

Do you know where you can buy a resistor such as the one in the back of the gauge?

oakley_77

Does anybody else have tips for this problem?

7T1vette

From your description, I'm guessing [betting] that you've used some kind of thread sealant on the sending unit (either pipe dope or teflon tape). If so, you've just thrown an insulator into the temp gauge's electrical circuit. The threads on the sender are meant to provide an electrical 'ground' path for the system via the engine block.

...Roger...

What happens when you ground and unground the wire going to the sender ?

mrvette

Above, and also that the '72 takes a special olde tyme sender I UNDERSTAND is not available except through vette parts dealer....

it's not a standard production item anymore from any local supply house......

it will read funky....never says high enough.....

oakley_77

At first I tried it with teflon tape because I was afraid that it would leak. Then, I though that this could be the issue so I took it off and cleaned it. I then re-installed it without anything on the threads...still the same issue.

oakley_77

When I ground the wire on the frame or the block...it goes passed HOT.

7T1vette

If the sending unit is grounded to the block properly, then the sender must be a mismatched unit. You can order correct replacement senders from lectriclimited.com .

oakley_77

So I won't be able to find a sender for my 72 anywhere locally? Does everybody order from ecklers, lectric, wilcox? I have a TS6 sender installed in the car right now which appears to be sending the corerct ohms to the ohm meter...

...Roger...

Thats a good thing ,now whats it do when you just remove it from the sender with the key on ?

oakley_77

It goes to the left just a TAD...maybe 1\16 th of inch...

...Roger...

If you mean a tad left of the COLD mark then try one more thing if you will. Take your turn signal flasher and read the ohms across the 2 spades and then hook your sender wire up to the flasher like this pic and tell us what happens.And tell us the ohm reading on your flasher.

oakley_77

Can it still be a mismatched unit even though the correct ohms are showing on the multimeter? I've tried 4 of them as of yet...including the original one that worked last year. The only thing that was done to the car over the winter was that we took off the Intake Manifold (cleaned and repainted) and replaced the carburator. I made sure that the the ground strap on the intake was sitting on bare metal.

oakley_77

I will certainly try that tonight. I am presently at work. I should be home in about 4hrs. That's the first thing I will do once I get there.
Thanks again!

...Roger...

Hopefully your flasher will be around 54 ohms which should give you a dash reading around 250 degrees--if it does then your problem is in the sender or the grounding of the sender. Here is a thread with a list of ohm readings and temps. Good Luck
http://forums.corvetteforum.com/c3-t...uld-share.html

oakley_77

Hi there,

I couldn't get my hands on a flasher but my mechanic gave me his Instrument cluster tester.
When I test the gauge at 0 ohms, it only goes to about 230 degrees...not past 250 degrees. I also have another gauge here that does the same thing. this is really confusing me. Plus, this was bench tested with a battery tester...not with the car wiring. What do you think it means?

...Roger...

Some of those old testers aren't very reliable. You can pop your hazard warning flasher right out of your fuse box and test with that.