1976 coolant temp sensor part number needed

[Itali83]

Hey guys. I need a known correct number for the temperature sensor for my 76 gmc. It’s for the gauge. I looked it up on maps, bought it and installed it only to find out it pegs the gauge to hot when it’s cold. Unplug the sensor and gauge returns back to to wherever the gauge wants to. I know my cluster is good and gauge is good. Napa is notorious for being wrong especially with the temp sensors and all the different resistances throughout the years of these trucks.

I have the sending unit that came out of it buts like nothing I’ve seen before and don’t think it’s correct.

I should add that there is only the single wire coming from the cab for the gauge. That’s all good and I know works because again, if I ground it or just hook it up to the sensor it pegs the gauge. I did NOT test resistance of sender because the engine was hot and I was in the middle of tuning the carb. I’ll check if the sensor is dead shorted and then I’ll know if it’s just a bad sensor.

Ben

 

[dsteelejr]

Are you sure it’s the sender for a truck with gauges and not the switch for trucks without gauges (idiot lights)?

The SENDER is for a gauge, the SWITCH is for an idiot light.

Very similar and easily confused (I’ve made that mistake before).

 

[Itali83]

The part number I got was listed for a gauge. Totally understand how it can be confused. Not saying that the part isn’t listed incorrectly. I’ll ohm it out tomorrow to see if it’s a dead short or not.

But, if I were to put a switch in there instead of the sending unit, it wouldn’t peg the gauge when cold or even operating temperature. It would only let the gauge if it overheads, closes the contact to ground then the gauge would peg. I still think it’s a wrong resistance sensor but have nothing known good to compare it with. All of my other squares are from the 80’s and I know they’ve changed by then


Ben

 

[dsteelejr]

The part number I got was listed for a gauge. Totally understand how it can be confused. Not saying that the part isn’t listed incorrectly. I’ll ohm it out tomorrow to see if it’s a dead short or not.

But, if I were to put a switch in there instead of the sending unit, it wouldn’t peg the gauge when cold or even operating temperature. It would only let the gauge if it overheads, closes the contact to ground then the gauge would peg. I still think it’s a wrong resistance sensor but have nothing known good to compare it with. All of my other squares are from the 80’s and I know they’ve changed by then


Ben

Since you mentioned that you’ve received incorrect parts from Napa in the past it’s just the easiest thing to check. On my 1980 K25 454 I use that sender I posted, part number TS71 and it works fine for me. I don’t have much experience trouble shooting temp senders. I read another post on here that @Bextreme04 replied to and he seems to have some expertise with it. Maybe he can help you figure it out better than I can.

 

[Termite_Delight]

I used an AC Delco G1852 on my 1976 K25.

 

[Itali83]

Thank you. That number crosses to the Napa number I got. I’m going to test the resistance and go from there. I found a chart online that shows the resistance throughout the temperature range so I can compare.


Ben

 

[John Nes]

That Delco G1852 is almost certainly the right one for your 76. The 1/2” -14npt nailhead style was used till like 79? 80? I wanna say I’ve read there were 3 diff coolant temp sensors for gauges, with matching gauges, that used different resistors to correspond with its sensor counterpart.

I just got all the factory gauges working on the project, and I think I went thru 4 trying to get the right one. Once was parts store sending down a switch instead of sensor, one was a dud out the box, one was the aforementioned, and just yesterday I got the right one so my gauge wouldn’t peg to Hot when I cranked it. Hope ya get it sorted

 

[Itali83]

John, do you have a part number and brand/store of the one that has your gauge working correctly?

Ben

 

[Itali83]

So I’m sure it’s a bad sensor. I found a chart with the temperature and resistance relation, and at 70*F the sensor should read roughly 650 ohms. Mine reads 1.8 ohms. Yup. Garbage. I’ll be bringing a multimeter with me to get the next one for sure.


Ben

 

[John Nes]

@Itali83 - I’d just go with acdelco, the shop I’m at has their largest account with AutoZone, and I’m not the biggest fan of Duralast parts, but you can always cross reference the Delco part from the duralast part… i used a TU-66 sensor (for late model trucks with gauges) 3/8” 18npt (with a 1/2” 14npt brass bushing reducer in between 1 + 3 on the driver side head)
Earlier squares used the duralast TU-65 1/2” 14npt.
I’d imagine if you mated the right era gauge with the right era sensor, your resistances should match and you wont have it pegging hot.

 

[75gmck25]

I can’t find all my notes, but IIRC the Standard Motor Products TS-6 is what worked for my ‘75 gauge, and it has the correct button-style connector.

The correct GM Delco sending unit is no longer available, and most newer ones don’t have the right resistance. There are discussions on other forums that have the original GM parts number, but I’d have to search for it, and it would have to be NOS parts.

My gauge now reads at just about quarter scale at about 190 degrees with the TS-6.

 

[Itali83]

I would think that 190 degrees should be more to the middle rather than 1/4 way. I may try another sensor as that would bug me thinking it was cold still


Ben.

 

[Octane]

I would think that 190 degrees should be more to the middle rather than 1/4 way. I may try another sensor as that would bug me thinking it was cold still


Ben.

My 77 350 has original nailhead type unit for my gauge,the gauge has always read at about 1/4 up from cold at 180° or so.Unless it's bad from factory....I've always assumed it was bad.lol

 

[Termite_Delight]

I can’t find all my notes, but IIRC the Standard Motor Products TS-6 is what worked for my ‘75 gauge, and it has the correct button-style connector.

The correct GM Delco sending unit is no longer available, and most newer ones don’t have the right resistance. There are discussions on other forums that have the original GM parts number, but I’d have to search for it, and it would have to be NOS parts.

My gauge now reads at just about quarter scale at about 190 degrees with the TS-6.

I got my sending unit on amazon, parts stores couldn't get it.

 

[Big red square]

Are you sure it’s the sender for a truck with gauges and not the switch for trucks without gauges (idiot lights)?

The SENDER is for a gauge, the SWITCH is for an idiot light.

Very similar and easily confused (I’ve made that mistake before).

Thank you for this i was very confused my gauge was stuck on cold and all the wiring was good.