Temp guage problem

[thinair]

My guage pegs in seconds flat! but the truck isn't overheating. The guage is good and the sending unit is new (broke the old one changing motors). I have the green wire ran to the sender. I do not have any power at the firewall on that wire. All the fuses are good. I soooo hate chasing electrical!!

[rfmaster]

Originally Posted by thinair

My guage pegs in seconds flat! but the truck isn't overheating. The guage is good and the sending unit is new (broke the old one changing motors). I have the green wire ran to the sender. I do not have any power at the firewall on that wire. All the fuses are good. I soooo hate chasing electrical!!

Look for a short - the green wire is touching chassis ground somewhere. Disconnect temp sending connector from the sensor. If meter remains pegged start tracing green wire all the way to the firewall plug (just under master cylinder) - you'll find it.

//RF

[matchstick321]

I just had a problem with my oil sending unit, it was leaking oil all over. Yeah what rfmaster said trace your wire back through your firewall plug. It's not that long of wire. And Idk what difference is in color code between years but on my truck the wire is orange.

[motornut]

should be green
is it the right sender?

[joe231]

I had the wrong sender in my CCSB.
I think it was a newer sensor. It would do just what you are saying.
It would jump up very hot very fast. I checked the radiator and thermostat housing with an IR thermometer, it was normal. I changed the sender to the correct one and it solved my problem.
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[rfmaster]

thinair

Please post your truck model year (and engine details). IRC 70's square bodies use single green wire (that's what I have in my 75) routed to a temperature sending unit bolted into driver side cylinder head. Trucks equipped with factory gauges can use SBP TS-6, or Wells TU-5 sending units if OE is damaged or no longer available. TU-5 appears to be the closest equivalent - not perfect, but good enough.

//RF

[thinair]

1982 K20, 350ci........ I thought about the wrong sender also ( I did buy it at a national parts store). The truck was originally a diesel. So I was thinking maybe diesel gauge/ gasser sending unit? But I removed the cluster and the part number on the circuit board is the same as a gasser that I have layin. When I hit that terminal on the firewall plug with the test light.....no power.
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[matchstick321]

Oh crap I'm sorry I was thinking of a completely different sender. haha I was tired when I read the thread last night... Yeah green wire... You havn't had it melt on your exhaust manifold had you? Do you still have your old sender to compare to your new one?

[rfmaster]

Originally Posted by thinair

1982 K20, 350ci........ When I hit that terminal on the firewall plug with the test light.....no power.
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That's because your temp sending unit circuit is shorted to chassis somewhere! Based on 1980 schematic our trucks used green wire tied to temp sending unit. The 81 to 87 wiring is different & IRC there a PDF scan detailing wiring harness posted in the older thread somewhere on this board. Do a search before doing any further digging.

//RF

[Corts60]

Sounds like your new sender has the wrong ohms, this happened to me on my '60. And I do believe the diesels had different senders but I doubt that is what they gave you unless you stated you had a diesel.

Try this link, I know a lot of guys on the 60-66 side have found there senders to be correct for the model year. http://www.lectriclimited.com/