TEMP GAUGE NOT WORKING

[1carlover]

Everything is working on my 67 RT restored dash with the exception of the temp gauge and I can't figure out why. I've installed the upgraded circuit board as well as new temp and fuel gauges and new temp sending unit. When I ground out the purple wire for the sending unit the gauge still does not move even though I'm getting 5 volts at the connector. I'm assuming that the temp gauge itself is not the issue since it is brand new but the needle wont budge. I would appreciate any input on how to get the factory gauge working before I give up and install an aftermarket mechanical gauge.

 

[AR67GTX]

My guess would be a bad connection at the firewall, bulkead connection plug. Might try tracing which one the purple wire leads back to, carefully unplugging it, do the best you can to clean the contact surfaces and firmly plug it back in again.

 

[Xp29h]

If bulkhead cleanup doesn't do the trick, I'd go get a new temp sending unit. I just replaced the gauges in my car and went aftermarket, had to use their temp sending unit. Maybe in the past the temp unit wasn't right for your newer setup? They're under 20 bucks usually.

 

[PurpleBeeper]

I'm with AR67GTX on this one. If you ground the wire where it plugs into the sending unit & get NOTHING at the gauge, and you have voltage at the gauge, that tells me that the purple wire isn't connected all the way to the gauge.... a broken connection somewhere. It "could" be a break in the purple wire itself. The "most likely" spot is at the firewall bulkhead disconnect for sure, but it could be elsewhere.

If it were me, I'd check that bulkhead connection....clean, dielectric grease, push the wire in from the back with a TINY screwdriver or something as my first try. If that didn't work, then I'd pull out a meter & start checking for continuity (resistance goes to near zero). 1st purple wire at bulkhead disconnect vs. the little plug at the sending unit. If that looks good, I'd start looking for continuity one section at a time under the dash all the way to the gauge (might be just one section, but may have a couple plugs....not sure)

 

[BeeKool]

Wouldn't be the first time a brand new sending unit was defective, also wouldn't be the first time if a brand new gauge was defective.

 

[1carlover]

Wouldn't be the first time a brand new sending unit was defective, also wouldn't be the first time if a brand new gauge was defective.

If bulkhead cleanup doesn't do the trick, I'd go get a new temp sending unit. I just replaced the gauges in my car and went aftermarket, had to use their temp sending unit. Maybe in the past the temp unit wasn't right for your newer setup? They're under 20 bucks usually.

I had a mechanical gauge hooked up awhile back and it worked without any issues before I began the dash restoration.

I'm with AR67GTX on this one. If you ground the wire where it plugs into the sending unit & get NOTHING at the gauge, and you have voltage at the gauge, that tells me that the purple wire isn't connected all the way to the gauge.... a broken connection somewhere. It "could" be a break in the purple wire itself. The "most likely" spot is at the firewall bulkhead disconnect for sure, but it could be elsewhere.

If it were me, I'd check that bulkhead connection....clean, dielectric grease, push the wire in from the back with a TINY screwdriver or something as my first try. If that didn't work, then I'd pull out a meter & start checking for continuity (resistance goes to near zero). 1st purple wire at bulkhead disconnect vs. the little plug at the sending unit. If that looks good, I'd start looking for continuity one section at a time under the dash all the way to the gauge (might be just one section, but may have a couple plugs....not sure)

Thanks for your replies regarding the bulkhead connector. I checked the bulkhead connection before I posted. I didn't think it was the issue since it was free of corrosion and still had fresh dielectric coating visible. I'm going to try to hook up an ohm meter to the gauge and check continuity then take it from there.

 

[Jcharger]

Continuity is a start. If you can put 5V or less DC through the gauge itself (polarity needs to be right), you can check to see if it responds. I believe the gauge is the same principle as the others, like fuel, but verify. You might be able to use that circuit to check if you don't have a 5V DC source.

 

[1carlover]

Wouldn't be the first time a brand new sending unit was defective, also wouldn't be the first time if a brand new gauge was defective.

Ive been thinking the same thing that maybe the gauge is defective but as it was purchased over a year ago I don't think Classic Industries will do anything about it and I'm not going to buy another one.

 

[BeeKool]

Ive had to replace gauges on old work trucks and tractors. The electric ones suck

 

[1carlover]

Since I have 5v at the temp sensor purple wire connector I'm going to clip a jumper wire to the back of the temp gauge, clip another on the other pole to ground and see if that does anything. If it doesn't move the needle then its probably a defective gauge that will have to wait until I need to take the dash out again. Its nice to be able to run these questions by guys on this site. Thanks to you and fbbo.

 

[Ethan]

Since I have 5v at the temp sensor purple wire connector I'm going to clip a jumper wire to the back of the temp gauge, clip another on the other pole to ground and see if that does anything. If it doesn't move the needle then its probably a defective gauge that will have to wait until I need to take the dash out again. Its nice to be able to run these questions by guys on this site. Thanks to you and fbbo.

I'm having the same issue. I installed 3 brand new gauges (fuel, temp, and oil pressure) along with a new board and a voltage limiter from RTE. All my gauges read but my temp gauge won't move at all. I also just put in a new sending unit. I used 10 ft leads, clipped one end to purple wire at sending unit and probed the other end at the plug where it goes into the circuit board under the dash and had flow. Super stumped

 

[Ethan]

I'm having the same issue. I installed 3 brand new gauges (fuel, temp, and oil pressure) along with a new board and a voltage limiter from RTE. All my gauges read but my temp gauge won't move at all. I also just put in a new sending unit. I used 10 ft leads, clipped one end to purple wire at sending unit and probed the other end at the plug where it goes into the circuit board under the dash and had flow. Super stumped

I could have gotten a bad gauge but I'm doubting that considerthats why I ordered a new one. Wondering if it can't be a ground issue. The purple wire (sending unit) goes to the board. Where is the ground for that?

 

[AR67GTX]

Is your instrument panel fully installed when you are testing it - all screws to the dash installed? I have a GTX which may be slightly different but it has a metal grounding strip on the top of the cluster that the upper cluster to dash frame screws pass through and complete a ground. I think trying to check instruments without it screwed to the dash can result in malfunction due to lack of ground - not completely certain of this but that's my impression. You can probably clip on a ground to the dash frame as a substitute for testing.

 

[miller]

The purple wire (sending unit) goes to the board. Where is the ground for that?

Do an ohms test, from the sending unit's metal body, to a good ground under the hood. Sending unit grounds to the engine, engine to body/frame via the engine ground strap. If you have some kind of sealant on the unit's threads, might not be making ground.

 

[1carlover]

The sending unit checked out and have determined the problem is with the repro gauge. I had no desire to take the dash apart again so I recently installed a mechanical temp gauge along side an oil pressure gauge and it works great.