94 temperature gauge issue

[Smitha]

If this is already posted i apologize. i just couldnt find it. i have 94 v6. The temp gauge was hardly going above 100 on road trip. Replaced thermostat and it went to about 1/4 mark. Just replaced both sensors and now gauge goes to complete max hot after about a minute. Engine runs fine and not low on coolant. Any ideas?
Thanks

 

[Schurkey]

Installed a switch instead of a sending unit?

Wires grounded? Rubbed bare, conductor touching something it shouldn't?

Wrong temperature range on the sending unit?

 

[stutaeng]

I had an issue with my truck a few weeks ago. I got the wrong sender from the parts store and was reading "overheating." See here:

https://www.gmt400.com/threads/overheating-after-changing-temperature-sender.48791/page-2

Some sender numbers are also referenced.

 

[someotherguy]

Yes, going from "reading too cold" to "reading max hot" absolutely sounds like the incorrect part used.

Once you get back to the correct sender, and then address any potential ground problems - at and next to the thermostat housing, from the battery to the fender, the two straps from firewall to rear of passenger cylinder head and same spot on firewall to the frame, and finally the dash cluster ground attached to the tab under the dash same spot as the ALDL connector.. once all those areas are addressed and sure to be connected, clean, and tight.. and the gauge still reads low?

Verify the engine's actual temperature with an IR temp gun aimed at the intake around the thermostat housing, scan for max temp, with the engine fully warmed up. If it's not reading close to 195F then you may have the incorrect thermostat or it may be defective. Fan clutch could be stuck engaged. Etc.

If you ARE reading close to 195F then you re-pin the needle on the cluster to a known setting. Engine fully warmed up, double check with the temp gun, gently pull the needle from the cluster and re-install it at the correct spot. None of these gauges are accurate, but you can at least put them where they belong when measured against an accurate tool like the IR temp gun. That way when it's colder or hotter than the known setting, the gauge should reflect that.

Richard

 

[Smitha]

Installed a switch instead of a sending unit?

Wires grounded? Rubbed bare, conductor touching something it shouldn't?

Wrong temperature range on the sending unit?

i know its a sending unit just cause the connections are different. I will check for bare wires. Thanks!

 

[Smitha]

I had an issue with my truck a few weeks ago. I got the wrong sender from the parts store and was reading "overheating." See here:

https://www.gmt400.com/threads/overheating-after-changing-temperature-sender.48791/page-2

Some sender numbers are also referenced.

Thank you! Not sure how it could be the wrong sender since it plugged right in but i will double check.. From reading the link almost make me think its got air in the system.

 

[stutaeng]

Thank you! Not sure how it could be the wrong sender since it plugged right in but i will double check.. From reading the link almost make me think its got air in the system.

What's the model number you put in? Yes, air in the system is a possibility, as is a faulty NEW sender. After messing with mine, I found out the Haynes manual has a table for temperature senders. They list a temperature and corresponding resistance in Ohms. If you have a DVM, you can double check this by heating the sender with a heat gun or hair blow dryer.

 

[Smitha]

Yes, going from "reading too cold" to "reading max hot" absolutely sounds like the incorrect part used.

Once you get back to the correct sender, and then address any potential ground problems - at and next to the thermostat housing, from the battery to the fender, the two straps from firewall to rear of passenger cylinder head and same spot on firewall to the frame, and finally the dash cluster ground attached to the tab under the dash same spot as the ALDL connector.. once all those areas are addressed and sure to be connected, clean, and tight.. and the gauge still reads low?

Verify the engine's actual temperature with an IR temp gun aimed at the intake around the thermostat housing, scan for max temp, with the engine fully warmed up. If it's not reading close to 195F then you may have the incorrect thermostat or it may be defective. Fan clutch could be stuck engaged. Etc.

If you ARE reading close to 195F then you re-pin the needle on the cluster to a known setting. Engine fully warmed up, double check with the temp gun, gently pull the needle from the cluster and re-install it at the correct spot. None of these gauges are accurate, but you can at least put them where they belong when measured against an accurate tool like the IR temp gun. That way when it's colder or hotter than the known setting, the gauge should reflect that.

Richard

Im just not sure how it would be the wrong part used since the connector clip is different from the sensors but i will check it. Thank you for everything else you have mentioned and others. Appreciate the help!

 

[stutaeng]

Here you go.

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[Erik the Awful]

not sure how it would be the wrong part used since the connector clip is different

That's no guarantee. This is GM we're talking about. Which connector they used was less what the engineers wanted and more what the accountants bought.