temp gauge not working

[mexlokote]

based on images

A - wire is not connected, i dnt know where should it go connected at,

B - wire is connected directly to the temp sending unit,

based on the diagram that is on my haynes repair manual they go both connected together somehow i do not know how, im not sure what the diagram is telling me,

gauge is not working it stays in cold, but i do have some overheating issues but i want to fix the gauge first, the A - wire which is disconnected i tried grounding it and it does send the gauge all the way to hot,, anybody has any idea where can this A wire go connected at,

i have new choke,sending unit and thermostat and already checked the fuses which are fine,

[motornut]

when i changed to gauges from idiots i only found one wire from the block to the firewall
can't say about the other
pretty sure those A&B parts are in the cab,not under hood

[hatzie]

Originally Posted by motornut

when i changed to gauges from idiots i only found one wire from the block to the firewall
can't say about the other
pretty sure those A&B parts are in the cab,not under hood

X2. A & B are inside the cab. The sender should only have 1 wire.

[mexlokote]

the A wire that is disconnected i followed it and it ends beside the brake booster and its just hanging there it needs to be connected i will post new pics tomorrow,

i think the A wire that is disconnected, is the one that runs from the ignition and meets at the firewall with the temp sending unit wire

[hatzie]

I don't like those aftermarket wiring diagrams you find in Haynes, Mitchell, and other manuals. They are confusing because they are always incomplete (in this case there's no note about the wire you labeled A). That's why I scanned and posted PDFs of the 73-91 GM OEM diagrams.

I don't have 1981, 1982, or 1984 diagrams yet. However... If you download and look at the GM wiring diagrams for 1980 & 1983 there's no difference in the temp sender circuit #35.

In the engine compartment there is a single Dark Green wire Circuit #35A running from the bulkhead plug to the temp sender/switch. I don't know what the other green wire is but it's not for the temp gauge circuit.

With gauges there is a single #35B wire at the cab side of the bulkhead plug. According to the notes the only clusters that have the extra circuit #35A on the cab side are the base model idiot light clusters.

1. Circuit #35B from the bulkhead plug (cab side) to the instrument cluster
2. Circuit #35A, NOTES; [omitted with gauges (1980), Base Only (1983)], from the bulkhead plug (cab side) to ignition switch ground #1. If you are converting to gauges you'll need to remove this wire.

[mexlokote]

thats what my gauges look like
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[mexlokote]

also when i went to autozone to buy the new temp sender unit, they askit was a gauge or light and i told them a gauge so they gave me the temp sender unit and i came home and tried to put it on and it was too big i wouldnt fit so i went back to autozone and i asked and they gave me the light sending unit, and i came home and it fit perfect, i dnt know if autozone has it mixed up or something is going on with my truck because when i first bought it not running, i got it running and one time it overheated and the gauge worked perfectly, this happened after i did a rebuild of engine i unhooked many wires,
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[mexlokote]

i pulled the A wire from the harness and thats what i got u can see on the picture
the other green one u see that one goes connected to the temp sending unit
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[hatzie]

Does the connected wire run to the correct position on the bulkhead plug?

[mexlokote]

the connected runs from temp sending unit to the firewall,
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[pontgta]

are you sure that you have the right (A)wire hooked up to the temp sending unit? should be on the left side left side in the middle of 1 and 3 cyl.. If you grounded that(a)wire and the guage went to hot then that the wire that should go to the sending unit... on mine i have one wire...and i think it goes straight to the guage from the sending unit. You need the sending unit(guage)...i think mine has an adapter of some sort...I could be wrong...I will check tommorrow and let you know...


basically the sending unit is ground(when hot)...power is on the other side of the guage.....that is all that is needed to make it work...

[mexlokote]

both wires when grounded make the gauge go to hot it used to work perfectly fine and the temp sending unit is not beside the engine its in front of the engine right where the thermostat is
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[Skunksmash]

These gauges are a joke I'd get a new one. Mine was 35 degrees off all the time.

[mexlokote]

where can i get a new one also what if i buy one from autozone to rewire it and hang it somewhere inside the cab
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[hatzie]

Originally Posted by mexlokote

also when i went to autozone to buy the new temp sender unit, they askit was a gauge or light and i told them a gauge so they gave me the temp sender unit and i came home and tried to put it on and it was too big i wouldnt fit so i went back to autozone and i asked and they gave me the light sending unit, and i came home and it fit perfect, i dnt know if autozone has it mixed up or something is going on with my truck because when i first bought it not running, i got it running and one time it overheated and the gauge worked perfectly, this happened after i did a rebuild of engine i unhooked many wires,
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Originally Posted by mexlokote

both wires when grounded make the gauge go to hot it used to work perfectly fine and the temp sending unit is not beside the engine its in front of the engine right where the thermostat is

If either wire nails the gauge when grounded then the gauge is working. You probably have the wrong sender.

The original temp sender is screwed into a hole in the Left Hand cylinder head that's inline with the spark plugs. You prolly have a plug where the sender is supposed to screw in. Using a sender in the intake is problematic because the intake is the high point in the cooling system. If all is well it should read the coolant temp just fine. However. If you develop a coolant leak the sender will be reading an air pocket temp and not the temp of your overheating engine.

The stock temp sender for the earlier builds of these trucks is 1/2-14 NPT. If you have early stock heads the Standard Motor Products TS6 is the right sender. Popular later model heads, like the Vortec, use a 3/8-18 NPT sender. The 3/8-18 NPT senders started to be used in 1986, or a little before, so the Standard Motor Products TS76 or an equivalent should work.

You need to be careful to stay with the 1980's 3/8-18 NPT senders. The stock sender ohms out 13KΏ-34KΏ Cold and 60Ώ Hot. Some later senders, but not all, are the opposite... low Ώ cold and high Ώ hot. Take a meter with you to the parts store and check the Ohmage on the new sender. If the new sender is 13KΏ to 34KΏ cold it'll probably work.

[motornut]

I had to use an adapter to fit the smaller sender into the larger hole
this is both the oil and temp I used .....
TS76 - temp

[mexlokote]

i have solved the problem! i found the old temp sending unit and saw that it was different from the one i got at junkyard and diff from the new one i bought, u can see on the picture the first one is the old one the original when i first purchased the truck, and the middle one is the one i got at the junk yard is the one i used after i rebuilt the engine,
so i just cleaned the old one really good and worked perfect, thanks guys for all ur help
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[chevybuilder18]

Originally Posted by mexlokote

the A wire that is disconnected i followed it and it ends beside the brake booster and its just hanging there it needs to be connected i will post new pics tomorrow,

i think the A wire that is disconnected, is the one that runs from the ignition and meets at the firewall with the temp sending unit wire

theres a thermometor looking thing in the side of the cylinder head to take engine temp, think thats were it will hook up

[chevybuilder18]

Originally Posted by mexlokote

i have solved the problem! i found the old temp sending unit and saw that it was different from the one i got at junkyard and diff from the new one i bought, u can see on the picture the first one is the old one the original when i first purchased the truck, and the middle one is the one i got at the junk yard is the one i used after i rebuilt the engine,
so i just cleaned the old one really good and worked perfect, thanks guys for all ur help
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ok you have the same thing i got and please ignore my last post, sorry didnt know you figured it out. the one on my block currently is a circle kind plug looking? how do you wire that up?

[mexlokote]

i have no idea
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[motornut]

slides on from the side,one side of the the white has a groove?ends up like an L
long side the wire,short the sensor,instead of straight in

[motornut]

my 79

[3672300]

Hey the guy I just bought my latest V10 (1987) from installed an aftermarket temp gauge, sigh. I want to go back to the original OEM gauge in the dash. Where can I get a new cable and sending unit to hook it back up like it was from the factory? Are these readily available from like LMC, or is there a better alternative?