'72 C-10 307 Water Temp Sending Unit

[C10 - C90 Bill]

On a '72 C-10 307 V-8, from the factory for a Water Temp Sending Unit for an Idiot Light, did it have 1 Prong or two?

Thanks

[LockDoc]

Originally Posted by C10 - C90 Bill

On a '72 C-10 307 V-8, from the factory for a Water Temp Sending Unit for an Idiot Light, did it have 1 Prong or two?

Thanks

First picture is sender for gauge, second is for light.

LockDoc

[C10 - C90 Bill]

Great pictures, thanks.

Bottom one is exactly what I need. Was having trouble finding one.

[tutone]

Not sure about the teflon tape on it though. I think the metal to metal is your ground.

[dmjlambert]

I believe a couple of wraps of teflon tape is OK. Enough of the metal will cut through the tape and make good ground contact.
The temperature switch is Wells or AutoZone part number is TU51 if the hole where you are putting it is threaded for 1/2 NPT size, and TU78 if the hole is threaded for 3/8 NPT.
TU51 turns on at 251 F +/- 10 degrees, and TU78 turns on at 240 F +/- 10 degrees.

[C10 - C90 Bill]

Appreciate the additional replies.

[Accelo]

GM didn't want annoyance activation of the overheating lamp did they?
240 might be OK. Definitely pass on the 250 deg switch.
Considering even the lower temp switch is 6O deg over what the design temperature.

I am unsure where the switches were manufactured but I am not a fan of the overseas temperature anything. I have been burnt bad by them. I only use them when I have no other choice. Then I check them against the factory resistance and temperature. They are typically way off. I have been able to correct them by adding resistance to the feed wire. Since most of our truck use gauges OEM the OEM switches can be picked up for little money on ebay.
https://www.ebay.com/itm/28488051378...Bk9SR4jczbu1YQ
This one is $15 and free shipping.
Others for as little as $8.
Here is the search terms I used. Copy it with the brackets. (6490128,6490793)
I believe the part numbers are correct, possibly somebody will confirm.

BTW the Teflon tape, shown on the switch, is installed by the manufacture.
GM didn't do this and doesn't recommend installing tape. Just an indicator of how much research they put into their parts.
I also agree it likely will not typically make a difference on the grounding. However, I don't use tape and never had one leak.
Cheers

[C10 - C90 Bill]

Update: Still having trouble finding the correct one. When I went to Rock Auto it only showed a 2 Prong for my application. Also when I typed in both TU51 and TU78 at Autozone, it stated "Does Not Fit Your Truck" ('72 C-10 307 V-8)

[LockDoc]

Originally Posted by C10 - C90 Bill

Update: Still having trouble finding the correct one. When I went to Rock Auto it only showed a 2 Prong for my application. Also when I typed in both TU51 and TU78 at Autozone, it stated "Does Not Fit Your Truck" ('72 C-10 307 V-8)

Does your temp sender wire have one connector or 2? What size are the threads on the sender, 3/8's or 1/2 inch? I am presuming you have the indicator light dash and not gauges.

LockDoc
.

[kev2809]

you have to be careful with rockauto and even the auto parts stores. rockauto listed a temp sender for my truck and it was no where near the correct range...even though it listed as correct, and it was the only one they showed. i would second the comment above about ebay. only search for the part number instead of what fits your year model, they arent always correct.

and x3 on the tape, i didnt use any on my threads and not a single drop comes through

[C10 - C90 Bill]

Originally Posted by LockDoc

Does your temp sender wire have one connector or 2? What size are the threads on the sender, 3/8's or 1/2 inch? I am presuming you have the indicator light dash and not gauges.

LockDoc
.

1 Prong. That's why when you posted a picture of the 1 Prong for a Light, which is what I have, I figured that that be the correct one, but I can't find the Part Number for it. Not sure on the Threads yet, but most applications show just one. Although they either have 2 Prongs or a Round Prong for a Gauge application. No luck on a 1 Prong. Believe GM may have given me an out-of-the-ordinary set up.

[C10 - C90 Bill]

Originally Posted by kev2809

you have to be careful with rockauto and even the auto parts stores. rockauto listed a temp sender for my truck and it was no where near the correct range...even though it listed as correct, and it was the only one they showed. i would second the comment above about ebay. only search for the part number instead of what fits your year model, they arent always correct.

and x3 on the tape, i didnt use any on my threads and not a single drop comes through

Maybe the TU51/TU78 from Autozone will work??

[LockDoc]

-
Look at this one....

https://www.classicindustries.com/pr...arts/tu45.html

LockDoc

[OregonNed]

I was very happy with the one I purchased from Lectric Limited - but it was $25

[dmjlambert]

Originally Posted by C10 - C90 Bill

Update: Still having trouble finding the correct one. When I went to Rock Auto it only showed a 2 Prong for my application. Also when I typed in both TU51 and TU78 at Autozone, it stated "Does Not Fit Your Truck" ('72 C-10 307 V-8)

I think Autozone's fitment data is probably lacking accuracy. TU51 does fit a 1969 C-10, and Autozone's website also says that. When you click the link on Autozone that is for showing the switch that fits 1972, it sends you to parts that are listed as switches, but just looking at them it is apparent they are gauge sensors and not switches. (edit: apparent to me because of the terminal shape and comments people have left that indicate they are working with gauge clusters, but I would have to test one with an ohm meter to be sure)

I think a switch that switches on at a desirable warning temperature will work with a 67-72 instrument cluster with warning lights. The light is either on or off, so the thing that will make a difference is what NPT size hole is in the engine head. The TU78 part is for 1982-89 Chevy truck and is suitable for an older truck if your older truck has 3/8 NPT hole in the head because the engine was refreshed with an engine or engine heads that are newer and have the smaller hole, like mine. I have the original 1969 engine with 1992 heads on it, so the hole is 3/8 NPT. I researched it for my truck and posted here what I found: http://67-72chevytrucks.com/vboard/s...d.php?t=726025

If you want to have high confidence I think it is necessary to put a coffee can of antifreeze and water mixture on a stove or outdoor propane cooktop and put a candy thermometer and the switch in the mixture connected to an continuity tester or test light, and verify at what temperature it switches on.

[dmjlambert]

I'm sorry I didn't give the whole story and link to my research in my first reply. I thought it may be too much to read, but then again everybody needs a certain degree of confidence when outfitting a truck.

[C10 - C90 Bill]

Appreciate the additional replies. I now have more to check into.

[cwcarpenter98]

I purchased a sending unit for my 63 from Letric Limited. It works perfectly with my original gauge.

[dmjlambert]

Yes, I think Letric Limited is renowned for a good sender for gauge instrument clusters, but for this thread we have been discussing warning light instrument clusters. The sender for a warning light instrument cluster is a switch with flat blade terminal.