Update on my 1985 Cavalier which the fan will.

Tiny
BTETRA
  • MEMBER
  • 1985 CHEVROLET CAVALIER
  • 102,000 MILES
Update on my 1985 cavalier which the fan will not come on: Thanks Caradiodoc ! I disconnected the the wires from the coolant sensor the fan comes on. If I stick a test light in to grn/wht wire on the relay the fan comes on. The wiring is like a 1986 cavalier, it does not have a coolant fan switch as pictured on the 1985 wiring diagram. No luck on a scan tool because I have the old style connector. I presume the problem is in the low volt section, how do I trouble shoot it?
Friday, January 11th, 2013 AT 1:12 AM

8 Replies

Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
The dark green and white wire is the back up fan switch when it reaches the correct temp it grounds that wire that goes the relay to trigger it that's why the fan comes on when you hook it to a test light. So which engine do you have?
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Friday, January 11th, 2013 AT 1:31 AM
Tiny
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Saturntech9 : thanks for the reply. The engine is a 2.0. Another thing when checking the codes with the jumper wire in the scan tool connector, if the switch is turned to ON the fan will come on. I really appreciate you guys helping me with getting my car going.
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Friday, January 11th, 2013 AT 2:31 AM
Tiny
SATURNTECH9
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Thats normal also when you jump the connector into diagnostic mode the fan will turn on. So the coolant temp sensor isn't on your car?Just the back up fan switch you unplugged? If so sounds like the fan and the fan circuit s good and you have a bad fan switch.
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Friday, January 11th, 2013 AT 2:43 AM
Tiny
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Yes I have the temp sensor but do not have a fan switch that is shown for the early 1985 models. Chevy parts said that the car was made in late 1985 and that was the reason there was no fan switch. I have put 3 temp sensors thanks to Advance auto trying to help me get the car going. I have been fixing my personal vehicles for over 50 years but this has me stumped.
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Friday, January 11th, 2013 AT 3:33 AM
Tiny
SATURNTECH9
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So if you ground the wire going to the sensor does thefan come on?
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Friday, January 11th, 2013 AT 4:20 AM
Tiny
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Yes.I grounded the original and the fan come on. If I disconnect the male connector it comes on. I bought a manual and it did not help that much. It said not to ground so haven't done it anymore.
Tested this morning:
5. Volts on the yellow wire: when plugged up drops to 3.7 volts connected. Hot drops to 1.3 volts
*Temp sensor.1780 ohms resistant cold
*temp sensor. Hot 170 ( in range of factory spec. 1800/200)
Also the fan will come on when I turn the A/C on.
Thanks for the help !

*Engine coolant temperature sensor
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Saturday, January 12th, 2013 AT 8:09 PM
Tiny
SATURNTECH9
  • MECHANIC
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Where going to have to get a scan tool that can read live data on that car to see what temp the coolant temp sensor is reading to help diagnose the problem. What is the part number of the sensor you put in?Also what colors are the wires going to the sensor?
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Monday, January 14th, 2013 AT 4:56 PM
Tiny
BTETRA
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The sensor came from Advance Auto parts, made by BWD part number 3000T fits 1985 thru 1988 Cavaliers. Wires are yellow and black. Yellow goes into the sensor and the black goes back
to the ECM. Hopefully I got a friend that is opening his shop back up after an illness. He has a Snap On system, and I hope he has a plug that will scan the ECM. Thanks for your help.
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Tuesday, January 15th, 2013 AT 10:19 AM

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