Engine fan hardwired
Thread Starter
Racer
Joined: Feb 2012
Posts: 442
Likes: 23
From: Seattle Washington
Engine fan hardwired
I'm bringing this 85 back to life. Bought it about 2 months ago and I hate to tell you how much I already have
into it. However, I know what I have now and am almost through with the fix. QUESTION: I have found the engine fan is hardwired. Will have it corrected but I would like to know the most likley fix and more importantly what problems is this causing while left as is?
Thanks,
JW
into it. However, I know what I have now and am almost through with the fix. QUESTION: I have found the engine fan is hardwired. Will have it corrected but I would like to know the most likley fix and more importantly what problems is this causing while left as is?
Thanks,
JW
Race Director
Joined: Feb 1999
Posts: 12,772
Likes: 17
From: Indianapolis IN
ECU tells the main fan to come on using a relay, use the GM manual to determine the signal wire color / number to the Relay and see if the relay is in the engine bay some where setting languid or being by passed.
Racer
Joined: Sep 2007
Posts: 493
Likes: 0
From: Eden Utah
I'm bringing this 85 back to life. Bought it about 2 months ago and I hate to tell you how much I already have
into it. However, I know what I have now and am almost through with the fix. QUESTION: I have found the engine fan is hardwired. Will have it corrected but I would like to know the most likley fix and more importantly what problems is this causing while left as is?
Thanks,
JW
into it. However, I know what I have now and am almost through with the fix. QUESTION: I have found the engine fan is hardwired. Will have it corrected but I would like to know the most likley fix and more importantly what problems is this causing while left as is?
Thanks,
JW
I am assuming by being "hard wired" the fan runs all the time. If so not good... You need to get it back on the relay
Drifting
Joined: Oct 2006
Posts: 1,328
Likes: 14
From: Stafford Connecticut
It aint going to be that easy. I am chasing the same problem.I have the factory manual and all it says is the ECM controls the main fan.It doesn't say how.I changed the relay because it was melted inside.My main fan still runs all the time.
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
Mine has color diagrams and detailed flow charts that direct you thru the entire system piece by piece.
The 2 book set is what I am refering to. One book for mechanical/tuning with the 2nd book strictly electrical with diagnosis. These books tell you how to ID all the pieces, what they are, what they look like, where to find them and what they're called.
Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 13
Two different scenarios.
You have a switch on the A/c and supposedly in '85 only a mechanical switch for the fan.
If either of those are faultly the fan would run full time ; key on
Fan will also run if the ECM is in limp home mode
Tests to be done.
Le Mans Master
Joined: Dec 2002
Posts: 5,270
Likes: 3
From: Seattle Area WA
You basically need to check the wiring and verify the relay works. A relay can fault and provide constant power.
Unplug the fan, start tracing wires back. My 86 has the fan relay on the driver's side fender right where it starts bending back to the battery.
Wires ok to the relay? (mine was spliced in this section to a random switched 12v...)
Test relay?
If the relay is good and the wires are good then it may be a switch or ECM but I'd bet it is one of those first two.
Unplug the fan, start tracing wires back. My 86 has the fan relay on the driver's side fender right where it starts bending back to the battery.
Wires ok to the relay? (mine was spliced in this section to a random switched 12v...)
Test relay?
If the relay is good and the wires are good then it may be a switch or ECM but I'd bet it is one of those first two.
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Drifting
Joined: Oct 2006
Posts: 1,328
Likes: 14
From: Stafford Connecticut
I just got back from checking all those items because my fan runs all the time.I removed the CTS wire fan still ran.I disconnected the switches to the air conditioner fan still ran.I swapped relays fan still ran.I put in my spare ECM fan still ran.I changed chip in ECM with one that is supposed to turn fan on at 200 degrees off at 180 fan still ran.The only time the fan stops running is when I turn the Vette off.It's driving me nuts.I do have a solution coming.It's a switch from Eclers that will run both fans at 200 degrees on 180 off.It goes in the head on the drivers side to replace the factory auxiliary switch
Last edited by steven mack; Mar 3, 2012 at 01:17 PM. Reason: Add info
Le Mans Master
Joined: Dec 2002
Posts: 5,270
Likes: 3
From: Seattle Area WA
I just got back from checking all those items because my fan runs all the time.I removed the CTS wire fan still ran.I disconnected the switches to the air conditioner fan still ran.I swapped relays fan still ran.I put in my spare ECM fan still ran.I changed chip in ECM with one that is supposed to turn fan on at 200 degrees off at 180 fan still ran.The only time the fan stops running is when I turn the Vette off.It's driving me nuts.I do have a solution coming.It's a switch from Eclers that will run both fans at 200 degrees on 180 off.It goes in the head on the drivers side to replace the factory auxiliary switch
BUT, your fans run even when the car isn't started and is just in the "ON/RUN" position? This is what mine did with the hardwire job. It wasn't obvious though, my wires were correct from the fan connector to the fenderliner and then inside some plastic wire loom I found the wire cut and spliced to another piece of wire that was in the loom to a junction and wired to a switched 12v. Without actually tracing all the wires, it looked as if there were no problems.
First step, check continuity from the connector for the fan relay to the fan connector. You'll want to check for continuity of the black wire with a red-stripe. This is the wire that takes the switched 12v from the relay and supplies it to the cooling fan motor. If you do not have continuity then there is probably a splice in there somewhere. If you do have continuity then start looking at relays (2 relays can be bad, easy to actually just test). Good luck.
PS. This applies to the original poster and Steven.
Le Mans Master
Joined: Dec 2002
Posts: 5,270
Likes: 3
From: Seattle Area WA
If your fans don't run with the engine off but key in the run position, it is probably something else but I'd still check. I thought when you said all the time you meant all the time except with the key off. I'll try to grab my FSM to check. This stuff is so annoying.
Le Mans Master
Joined: May 2006
Posts: 9,226
Likes: 9
From: Irvine Ca
People do this when their radiator is clogged with sediment/scale from putting tap water in their coolant system.
This is a good clue that your 85 most likely has cooling issues that you find in the Summer months.
There is a lot of good info posted as to how to rewire it back to stock.
I'd suggest pulling the radiator and having it boiled out, or getting one of those NOS from thepartsladi ($99 if I recall).
This is a good clue that your 85 most likely has cooling issues that you find in the Summer months.
There is a lot of good info posted as to how to rewire it back to stock.
I'd suggest pulling the radiator and having it boiled out, or getting one of those NOS from thepartsladi ($99 if I recall).
Le Mans Master
Joined: Dec 2002
Posts: 5,270
Likes: 3
From: Seattle Area WA
Well I don't think I can supply answers but have you tested the first wire yet? If not, just do this. Disconnect the connector from the relay, the fan should not run. This confirms you are powering the fans through the relay and not hardwired.
The next step varies based on your results.
The next step varies based on your results.
Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 13
It will do , ECM is in limp home mode with no CTS input
it will do ; need to jumper the A/c switch .Open switch sends signal to ECM to operate fan
Engine running or key on ; two different situations
As soon as key on you have power to the fan relay that if hardwired would make fan run full time
As USA said above; work out how the relay is currently wired
As simple as putting the relay control wire to ground will make fan run as soon as key is on
it will do ; need to jumper the A/c switch .Open switch sends signal to ECM to operate fan
As soon as key on you have power to the fan relay that if hardwired would make fan run full time
As USA said above; work out how the relay is currently wired
As simple as putting the relay control wire to ground will make fan run as soon as key is on
Last edited by vetteoz; Mar 3, 2012 at 07:36 PM.
Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 13
You already have all the wiring in place .Replace the relay/ connector
and run the control wire that used to go to the ECM to the new fan switch
Done
Le Mans Master
Joined: Aug 2010
Posts: 9,272
Likes: 17
worse comes to worse just buy a 90 fan harness and a thermal switch. Just take and run a wire from your starter to both relay orange wires (fused of course) then both red wires are hooked to an ignition feed (your fan fuse) then thermal sensor to both relay green and blue wires, then plug fan harness into motors and ground the other fan motor wire.
Tie in the a/c wire to the thermal sensor wire.
Dont use original fan relays go with later GM weatherpack relays and you will never have a problem. Take and mount the relay assemblies to the side of your radiator shroud and you are good to go & ecm has no more control of the fans.
Don't have to come from a vette of course, I used this setup from a 90's lumina in my 82 corvette to run it's dual fans. Isn't overly hard to wire up.
Tie in the a/c wire to the thermal sensor wire.
Dont use original fan relays go with later GM weatherpack relays and you will never have a problem. Take and mount the relay assemblies to the side of your radiator shroud and you are good to go & ecm has no more control of the fans.
Don't have to come from a vette of course, I used this setup from a 90's lumina in my 82 corvette to run it's dual fans. Isn't overly hard to wire up.
Drifting
Joined: Oct 2006
Posts: 1,328
Likes: 14
From: Stafford Connecticut
I'm going to do some more wire checks . If I can't find the problem wire I will run both fans with the Eclers wiring kit.Then both fans will run off the temp switch in the drivers side head.That is how the factory runs the auxiliary fan.I don't want to burn out any more wires.The Eclers kit will turn the fans on at 200 degrees and off at 185.Thanks for all the input guys.Steve
