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Broken wire on the Coolant Sensor causing the fans to stay on?

There may be a thread here that talks about this issue if you search for it. Also Gary's site has a nice link to walk you thru some testing. Nothing about both fans on always though but that is usually caused by the Sensor in the WP being unplugged and why I "assumed" a broken wire on that connector.

Caprice / Impala SS / Roadmaster | Innovative Wiring LLC
 

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Check the fan relays Could be stuck. How hot did it get? I Had relays stick on by themselves! Cracked it open, All worn inside. Quick "fix" Wacked them with a screw driver and they worked as intended once or twice before a replacement was had. Read the diagram on them and check it with a volt meter. No continuity should be between pins I forget and I forget :) If there is the relay is stuck. Then you can test the relay with a 12 volt source and see if it power flows through it when its energized. You can also check your fan wiring at the relay pins in the underhood box
 

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explain when and how this failure was created.

why did you replace both temp sensors ? typical problem is temp sensor on the WP will cause both fans to come on if bad connection .

T stat did not open so why did you replace both sensors .. did you test the old and new T stat in a pan of boiling water ? if not good chance the new is bad .

since you messed with the coolant a good chance that air is causing the fans to come on..
odd for the relays to be locked on since with the hot weather ac on both fans do come on often in the high heat ac working.

good luck,
 

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There are a few errors of the engine control electronics will cause both fans to come on and stay on. Hook it up to a scanner and see what the car is trying to tell you
 

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you will not get any help since you did not explain what troubleshooting and other work to find what caused the over heating.

the computer and a scan tool is not gonna find the problem .
you have to do a pressure check could be a head gasket or a leak. that will cause this..

then you must check the T stats that they open properly in a pan of boiling water new/old..
you must do the bleeding at the goose neck if air comes out again and again then you may have a blown head gasket..

another problem could be though not all that common is the water pump impeller may not be rotating ..

so post what testing you did .. forget about computer electronic controls not gonna fix it .
 

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Discussion Starter #11
it overheated, boiled over because thermostat went bad. replaced it and that fixed the problem. now runs cool. driven over 500 miles since. but since replacing thermostat both the fans come on after start and stay on causing a/c not to turn on. replaced sensors and connector and wires, all relays and fuses.
 

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Hi, if you're saying you verified the mechanical components are good [sensors,wiring, relays, etc] then something in PCM is telling fans to kick on.

If you have not there may be a short somewhere and making fans run all the time.
I wonder if the fact BOTH are running is a hint ? i would have thought one would run all the time with bad components...

Good Luck.
-ALF out...
 

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it overheated, boiled over because thermostat went bad. replaced it and that fixed the problem. now runs cool. driven over 500 miles since. but since replacing thermostat both the fans come on after start and stay on causing a/c not to turn on. replaced sensors and connector and wires, all relays and fuses.
well this is better info to help you .. possible the ac pressure switch high pressure is bad saying the high side refrigerant pressure is too high , so fans come on and the ac compressor will not turn on..

odd problem but it does happen..
 

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Discussion Starter #14
bought used 1996 ss impala pcm and had flashed to stock specs. didn't change anything. only thing changed is 180 thermostat to 195, but don't think that would make a difference. going to change back to 180 tomorrow.
 

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Get that 195 stat outta there pronto. 180 stat max,and most prefer the 160 degree version.
 

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bought used 1996 ss impala pcm and had flashed to stock specs. didn't change anything. only thing changed is 180 thermostat to 195, but don't think that would make a difference. going to change back to 180 tomorrow.
the pcm pin C4-12 is the pin that goes to the high pressure switch on the ac compressor .

so check that circuit /wire/sensor/connector ...

if that is bad then the both fans come on and the ac compressor clutch will not engage.
 

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Might try the 160 stat. Many of us use/recommend them...
 

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Won't hurt,costs little,and a good idea regardless....
 
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