'68 C60 temp gauge

[Triplel40]

Hello! I've been creeping around the forums for years and finally made an account. I have a '68 C60 farm truck with a 366 in it. The temp gauge never worked when I got the truck, but if you touch the sending unit wire to ground it pegs hot, so I know the gauge works. Being a C60 I couldn't find a sending unit listed for it anywhere. Working with my local NAPA guy we found a sending unit out of a 68 2500 396 truck that looks identical, but after installing it today the gauge still never gets off cold. Does anybody know what the resistance cold/hot should be for this truck's sending unit? Anybody know of where to get the right one? Any other ideas?

This is the sending unit I have now:
https://www.napaonline.com/en/p/ECHTS6469


~EDIT the old sending unit says "AC-Made In U.S.A.-12 VOLT" but I don't see any part numbers on it.
Thanks!

[LockDoc]

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There are two different sending units, one for the idiot lights and one for the gauges. I bet you have the wrong one. I can't tell you what the ohm readings should be but I would bet it's the sender..... Nice looking truck!

LockDoc

[demian5]

Dude with the dual thermostats and the huge radiator, it may never get warm! LOL!

But LockDoc is right. Some of those had an idiot light AND a gauge. One on each head.

[rkn463]

Originally Posted by LockDoc

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There are two different sending units, one for the idiot lights and one for the gauges. I bet you have the wrong one. I can't tell you what the ohm readings should be but I would bet it's the sender..... Nice looking truck!

LockDoc

The sender for the idiot lights is just a switch, normally open and closed if the temp is exceeded. If it is the wrong sender then it will just show open on the ohm meter during normal operation. I took a quick look at the part listed and it looks right. The one for the idiot light has a spade terminal and the one for the gauge has the round nub sticking out, you can see drawings on the LMC site, page 187.

Check the wire and make sure it is not damaged. Basically your temp gauge is an ohm meter, so anything affecting conductivity will make it read wrong. When I first got my 68 back together I was reading cold or barely registering. My wire had been cut and was twisted together and taped, when I fixed it with solder and heat shrink the problem was resolved.

-Richard

[Triplel40]

Definitely have the right sending unit between the two options I found. I stripped the insulation back off of the wire and it is pretty badly corroded inside. I'll run a new wire to the gauge tomorrow and let you know what happens!