DansYellow66

I bought a new temperature sender (duralast TU-5) to install some time ago and finally did so yesterday - but no movement out of my gage. I pulled the wire to the sender and grounded it and the gage shot over to the 3 o'clock position. Hooked it back up to the sender and it rocketed back around to the 9 o'clock position. Sort of figured that ruled out the gage since it rocketed back and forth. Seems to rule out the wire and bulkhead connector as the gage rocketed back and forth. May rule out the sender - probably need to test resistance but apparently it's pretty high resistance as the gage went way below the cold mark.

I did a search and low and behold I wrote a thread on this 3-1/2 years ago that I completely forgot about. Appears I did some testing at the time - of which I have no recollection of. Seems like the gage operated off and on for awhile after that but I haven't seen it move in at least a year now.

https://www.corvetteforum.com/forums...missing-2.html

I worked on the wire clip to make sure it's making a good connection and it's possible that I do have some air in the system as I drained the coolant down slightly to install the sender and my coolant recovery system still has a lot of water in it that wasn't pulled back into the cooling system. Other than an air bubble can anyone think of anything else I might be dealing with?

Factoid

65GGvert

Teflon tape won't stop it from grounding, the sender will still work fine with it. What was the actual temperature of the engine when you hooked it up and the gauge stayed left? Do you have an ohmmeter? Measure from the tip of the sensor to the engine block, post back what resistance you got. At room temperature it should read around 600 ohms or more, dropping as the car warms up. If you're running at 180 to 200 degrees, the resistance should read closer to 100 to 120 ohms

Donald #31176

You might have a defective sender. Measure its resistance.

DansYellow66

I actually used No Ox as a sealer (?) to ensure I had good continuity. Not so good a sealer as I had to tighten it twice after starting to stop minor leaks - but I hope that eliminates the possibility of an air bubble around it.

I did not test the resistance in the new sender yet although I did check the old one in the 3-1/2 year old thread and it tested good. When I ran it yesterday I was sort of surprised it didn't work, then disgusted and just put it away up on the lift. I went out today and did the grounding check. I was kind of surprised when I reconnected the sender lead after grounding it and turned the key on and it went all the way to the 9 o'clock position. Before it had been resting around the cold mark.

Weather has turned bad but as soon as I can I'll run it and check resistance. Thinking of running an auxiliary ground from the instrument cluster to a known ground also, although not putting much hope in that.

DansYellow66

Afraid my testing of the gage last week end must have fried it or something. Today it's stuck on 100 F and not moving no matter what I do to it.

Sender looks good:
At cold engine temp (66 F) it read 675 ohms
At 157 F on the sender it read 150 ohm
At 165 F on the sender it read 115 ohms
When the sender was 165 F the thermostat housing read 175 F and this was after a run down the road so overheating isn't a problem.

Ground the sender wire to the gage now and it stays glued on 100F. Remove the sender wire and gage stays glued to 100 F. Pulled the bulkhead connector and checked sender wire for continuity - OK. The harness was replaced on this car in the 90 during it's restoration and the contacts have been treated with dielectric grease. Hooked the connectors back up and still nothing at the gage.

So need to get me some 1/4x 20 dowel pins made up to move the cluster out to where I can pull the gage out and check it over and test for continuity from the sender to the gage connection.

This may be a subject for another thread but has anyone purchased replacement gages lately that have a properly silk screened face with correct thickness lines and numbering?