Cooling system help
Thread Starter
Intermediate
Joined: Jun 2021
Posts: 29
Likes: 3
From: Kentucky
Cooling system help
Ok going to say this will probably sound weird but here goes, my main fan quit working. My car got up to 260 and when I noticed (at the time I was parked) I took off and the temp went back down. After looking at some things like wires and fuses, I read my manual and it showed me some things about the fan control relay. After pulling the plug, a wire seems to be missing from it. I already found the blue wire cut and grounded out near the plug for the secondary fan, which runs all the time. So here’s my question. I need a picture of the plug and what wires come into it. I see the diagram in the manual but it doesn’t specify color. I tried testing by grounding out wires but obviously that won’t work when one is missing. Thanks for any help!! It’s a 1985 btw
Last edited by cindyncharles; Jul 17, 2021 at 07:50 PM. Reason: Forgot year
Racer
Joined: Feb 2020
Posts: 484
Likes: 110
From: Fairfax, Virginia
Both fans have the same relay. The Aux Fan relay is on the firewall, below the LH hood latch. The Main Fan relay is on the rear inside of the LH wheel well. Both relays are wired the same, both relays have 5 pins but only 4 are utilized.
Pin A; Black/Red output to fan motor
Pin B; Dk Grn/White Control input. (Main fan, from ECM, Aux fan from temp switch between cyl #6 and #8).
Pin C Dk Blue Hot with Key in RUN, CFAN fuse.
Pin D Red Hot at all times. From fuse links D and E at battery junction block.
Pin A; Black/Red output to fan motor
Pin B; Dk Grn/White Control input. (Main fan, from ECM, Aux fan from temp switch between cyl #6 and #8).
Pin C Dk Blue Hot with Key in RUN, CFAN fuse.
Pin D Red Hot at all times. From fuse links D and E at battery junction block.
Disconnect the coolant temperature sensor at the front of the intake, this makes the ECM run the main fan. It'll also make the car run like vrap, but it verifies whether or not the ECM can or cannot control the fan.
Thread Starter
Intermediate
Joined: Jun 2021
Posts: 29
Likes: 3
From: Kentucky
Both fans have the same relay. The Aux Fan relay is on the firewall, below the LH hood latch. The Main Fan relay is on the rear inside of the LH wheel well. Both relays are wired the same, both relays have 5 pins but only 4 are utilized.
Pin A; Black/Red output to fan motor
Pin B; Dk Grn/White Control input. (Main fan, from ECM, Aux fan from temp switch between cyl #6 and #8).
Pin C Dk Blue Hot with Key in RUN, CFAN fuse.
Pin D Red Hot at all times. From fuse links D and E at battery junction block.
Pin A; Black/Red output to fan motor
Pin B; Dk Grn/White Control input. (Main fan, from ECM, Aux fan from temp switch between cyl #6 and #8).
Pin C Dk Blue Hot with Key in RUN, CFAN fuse.
Pin D Red Hot at all times. From fuse links D and E at battery junction block.
Drifting
Joined: Jan 2021
Posts: 1,315
Likes: 385
From: Northern California
I would also fix that blue wire that just grounded to the brake master cylinder area. If I understood you correctly that's the wire normally attached to the coolant sensor for the secondary fan in front of the radiator/AC condenser right? Grounding it so that the fan runs all the time is not a great idea, it should be controlled by that coolant temperature sensor unless I'm wrong for the 1985 year. Your call though.
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Thread Starter
Intermediate
Joined: Jun 2021
Posts: 29
Likes: 3
From: Kentucky
I would also fix that blue wire that just grounded to the brake master cylinder area. If I understood you correctly that's the wire normally attached to the coolant sensor for the secondary fan in front of the radiator/AC condenser right? Grounding it so that the fan runs all the time is not a great idea, it should be controlled by that coolant temperature sensor unless I'm wrong for the 1985 year. Your call though.
Racer
Joined: Aug 2014
Posts: 478
Likes: 66
From: Elizabethtown, NC
Both fans have the same relay. The Aux Fan relay is on the firewall, below the LH hood latch. The Main Fan relay is on the rear inside of the LH wheel well. Both relays are wired the same, both relays have 5 pins but only 4 are utilized.
Pin A; Black/Red output to fan motor
Pin B; Dk Grn/White Control input. (Main fan, from ECM, Aux fan from temp switch between cyl #6 and #8).
Pin C Dk Blue Hot with Key in RUN, CFAN fuse.
Pin D Red Hot at all times. From fuse links D and E at battery junction block.
Pin A; Black/Red output to fan motor
Pin B; Dk Grn/White Control input. (Main fan, from ECM, Aux fan from temp switch between cyl #6 and #8).
Pin C Dk Blue Hot with Key in RUN, CFAN fuse.
Pin D Red Hot at all times. From fuse links D and E at battery junction block.
Thread Starter
Intermediate
Joined: Jun 2021
Posts: 29
Likes: 3
From: Kentucky
This is the fan control switch right? Secondary runs all the time so I have a black wire that’s added to the blue one that is ground out on the master cylinder.
Just the wire
This wire is black and ground out on the thermostat housing.
It got to 235 and I didn’t push it past that
Last edited by cindyncharles; Jul 20, 2021 at 05:08 PM. Reason: Add pic
Racer
Joined: Aug 2014
Posts: 478
Likes: 66
From: Elizabethtown, NC
Read this post as most people give you advise based on 1986 and up but the 1985's are different as to relay and fan switch placement on the cylinder heads. https://www.corvetteforum.com/forums...revisited.html
Thread Starter
Intermediate
Joined: Jun 2021
Posts: 29
Likes: 3
From: Kentucky
Read this post as most people give you advise based on 1986 and up but the 1985's are different as to relay and fan switch placement on the cylinder heads. https://www.corvetteforum.com/forums...revisited.html
Thread Starter
Intermediate
Joined: Jun 2021
Posts: 29
Likes: 3
From: Kentucky
I want to thank everyone for the suggestions on how to fix my car. After spending a while tracing wires around, I finally found a fusible link to the fan relay was bad. I cut it out and put a fresh link in, and tested the wire and it was hot. Started the car and turned on AC and heard the sweet music of the fan working. So, I drove it around so that I could get it to temps and even in traffic it stayed around 210. Just now took it out for a cruise without AC and at sitting still idling it hit 215 then the fan kicked on. I put the 195 deg thermostat in it and did ad everyone said I put a very small hole in it and it’s doing what it’s supposed to. Thanks again for the info!!
Thread Starter
Intermediate
Joined: Jun 2021
Posts: 29
Likes: 3
From: Kentucky
Thread Starter
Intermediate
Joined: Jun 2021
Posts: 29
Likes: 3
From: Kentucky