Question: cooling fan question here.

[vernh]

Hey everyone I am new here but have browsed the board for a couple of weeks. I recently bought my first corvette. A dream of mine since childhood. Anyways, it has sat for aprox. 7 years and I have solved many problems with it. But, One that is giving me fits currently is the cooling fans. I have read many suggestions but most are hard to follow and some of the switches and all is even harder to find. I was able to get my aux fan to run by jumpering it. I do know it will run. Now as for the main fan the one located between radiator and motor not sure where to jumper it to get it to run. Just to ensure it is working. I have turned on the AC and when I do no fans run. Does that mean the ECM is bad? Or could one switch make both fans unoperational. I guess I could have two bad switches but I hate to start changing switches and all just to be guessing. Currently car is not licensed so I reckon carrying it to a shop is out of the question. I was really wanting to get everything working so I could drive this bad boy. Any help would be greatly appreciated.

 

[vernh]

cooling fan question again

I have followed the wires from the main cooling fan. The black with red stripe wire appears to terminate at a relay mounted on the wheel well just infront of the battery. It has the same part number as the relay that I jumped to start the aux. fan. My question now is do both fans have their own relay? And, if they do does anyone know if I am at the right relay to test my main fan to see if it is good or bad? I did find on the driver side the piece mounted in the block the connector for it was broken. I stuck it on the best I could but engine still run hot and fans never came on. When key is off the main orange or red wire running to the relay isn't hot but once key is turned on it is showing 14 volts. Any help would be greatly appreciated. I also forgot to mention in my first post this is for a 1989 corvette.

 

[G Winter]

Providing the 89 is set up close to a 90 the relays are activated by grounding. They always have power to them when ignition is on.
There should be a wiring diagram on the relay , from that you should be able to determine which wire is ground. Memory not being
real good I think it was white and blue on my 90 either that or white and green . The diagram should show the coil in the relay, one
side will be 12 volt disconnect the wires and use a volt meter to check for the 12 volt. There is also a 12 volt power to the relay at all
times to power the fan. Hope this helps.
You really need a service manual if your doing any amount of work on this car.


Glenn

 

[boomdriver]

Yep...Glenn is 100% right on.

there are 2 relays. One for each fan. Forget that front pusher fan..its nearly as useless as lips on a woodpecker. Its the big sucker fan that MUST run right. That one should come on with a/c and when the engine temp hits 228. Thats Normal. The front fan comes on at 238-240.

Because ALL things are controlled by completing grounds, thats all thats necessary to make something run. Find the ground thats the link from the sensor/switch. If you simply take the temp sensor wire off and ground it the fans should run...
BUT..

You REALLY need a service manual to do these kinds of test/repairs. Other wise you risk doing great damage by grounding the wrong things.

E BAY has used sets of 2 books for $75.
Do a search here and there is a link here somewhere for new books for around $150. Search C4 FSM



You cannot work on a C4 without them...The electrical is too complicated and there are too many subsystems and things that are hidden.

BTW..
Welcome to my world!
Corvettes are addictive, so beware but ENJOY !

 

[vetteoz]

My question now is do both fans have their own relay? .

yes

The black with red stripe wire appears to terminate at a relay mounted on the wheel well just infront of the battery..
does anyone know if I am at the right relay to test my main fan to see if it is good or bad?

that is main fan relay

When key is off the main orange or red wire running to the relay isn't hot but once key is turned on it is showing 14 volts. .

Wrong.
That red wire should be hot all the time .
Only the blue wire should be hot ;Key on ( if not check fan fuse)
Maybe the fusible link blew and some previous owner has wired power to relay differently

Usual fan test is to jumper incoming red wire to outgoing red/black wire at the relay connector ;
only you will have to do it with key On as you have no power there with key off as it should be.

 

[vernh]

Thank you Glenn

Providing the 89 is set up close to a 90 the relays are activated by grounding. They always have power to them when ignition is on.
There should be a wiring diagram on the relay , from that you should be able to determine which wire is ground. Memory not being
real good I think it was white and blue on my 90 either that or white and green . The diagram should show the coil in the relay, one
side will be 12 volt disconnect the wires and use a volt meter to check for the 12 volt. There is also a 12 volt power to the relay at all
times to power the fan. Hope this helps.
You really need a service manual if your doing any amount of work on this car.


Glenn

 

[vernh]

did a jump at the relay fan wouldn't run. I replaced fan and now it will run when I jump it. But it still doesn't com on when it reaches temperature. The three amp fuse in the fuse panel do you know how it is listed other research has shown me it to be the 10 amp. fuse listed as ecm. I will go now and check for any 3 amp fuses and check them. Thanks for your help and diagram. I have made many repairs to the car already but this one is stumping me.

yes


that is main fan relay


Wrong.
That red wire should be hot all the time .
Only the blue wire should be hot ;Key on ( if not check fan fuse)
Maybe the fusible link blew and some previous owner has wired power to relay differently

Usual fan test is to jumper incoming red wire to outgoing red/black wire at the relay connector ;
only you will have to do it with key On as you have no power there with key off as it should be.

 

[vernh]

Boomdriver thanks for your help. Yes I can see how they are addictive. I have loved just sitting in the thing and running it for a few minutes at a time.

Yep...Glenn is 100% right on.

there are 2 relays. One for each fan. Forget that front pusher fan..its nearly as useless as lips on a woodpecker. Its the big sucker fan that MUST run right. That one should come on with a/c and when the engine temp hits 228. Thats Normal. The front fan comes on at 238-240.

Because ALL things are controlled by completing grounds, thats all thats necessary to make something run. Find the ground thats the link from the sensor/switch. If you simply take the temp sensor wire off and ground it the fans should run...
BUT..

You REALLY need a service manual to do these kinds of test/repairs. Other wise you risk doing great damage by grounding the wrong things.

E BAY has used sets of 2 books for $75.
Do a search here and there is a link here somewhere for new books for around $150. Search C4 FSM



You cannot work on a C4 without them...The electrical is too complicated and there are too many subsystems and things that are hidden.

BTW..
Welcome to my world!
Corvettes are addictive, so beware but ENJOY !

 

[vernh]

Checked three amp fuse in panel it checked good. I am wondering if I may have a bad ecm. I can jumper the main cooling fan once car is hot it begins to cool down. Once it reaches a certain temperature the aux fan will go off. Which I believe tells me that part of the ecm is working properly. I am wondering now if my ecm isn't ever telling my main fan to come on.

did a jump at the relay fan wouldn't run. I replaced fan and now it will run when I jump it. But it still doesn't com on when it reaches temperature. The three amp fuse in the fuse panel do you know how it is listed other research has shown me it to be the 10 amp. fuse listed as ecm. I will go now and check for any 3 amp fuses and check them. Thanks for your help and diagram. I have made many repairs to the car already but this one is stumping me.

 

[vetteoz]

I am wondering now if my ecm isn't ever telling my main fan to come on.

Possible but highly unlikely
At this stage would do more investigation of wiring
Do you have key on power at blue wire as noted in post #5?

If you ground the green / white at fan relay connector ( key on ) , fan should run ; if not relay is kaput
If it runs you may still have bad connection to ECM
Need to ground same wire at ECM connector before considering ECM problems

it begins to cool down. Once it reaches a certain temperature the aux fan will go off.

Aux fan not controlled by ECM,
See diagram I posted above , no connection back to ECM from aux fan relay

 

[vernh]

I do have power at blue wire when key is on. After having posted earlier I did notice that the aux fan isn't on the ECMper diagram. I then thought these guys are going to think I am a moron. I will ground the relay tomorrow and see what happens. I do think the relay is ok cause I swapped it out with the aux fan relay and aux fan still worked. Main reason I am thinking ECM is fan doesn't operate with ac on or with car over 230 degrees. I do appreciate all of your advice and help thank you.

Possible but highly unlikelyAt this stage would do more investigation of wiringDo you have key on power at blue wire as noted in post #5?If you ground the green / white at fan relay connector ( key on ) , fan should run ; if not relay is kaputIf it runs you may still have bad connection to ECM Need to ground same wire at ECM connector before considering ECM problemsAux fan not controlled by ECM,See diagram I posted above , no connection back to ECM from aux fan relay

 

[vernh]

fan did come on when grounding green and white wire at relay. Unhooked plug to ecm and checked wire to insure wire wasn't broken from relay back to ecm. ohmed out as though wire is solid. I guess now I just need to figure out where wires are grounded and make sure they are grounded properly.

I do have power at blue wire when key is on. After having posted earlier I did notice that the aux fan isn't on the ECMper diagram. I then thought these guys are going to think I am a moron. I will ground the relay tomorrow and see what happens. I do think the relay is ok cause I swapped it out with the aux fan relay and aux fan still worked. Main reason I am thinking ECM is fan doesn't operate with ac on or with car over 230 degrees. I do appreciate all of your advice and help thank you.

 

[boomdriver]

fan did come on when grounding green and white wire at relay. Unhooked plug to ecm and checked wire to insure wire wasn't broken from relay back to ecm. ohmed out as though wire is solid. I guess now I just need to figure out where wires are grounded and make sure they are grounded properly.

The key to C4 electrical is the GROUNDS. They control everything. Voltage takes a backseat to grounds on these cars. Why? easier to manage/control/less risk.
Locate the ground bubdle of 5 wires on a bolt near the oil filter. Clean and repair. Also clean and repair the hot wires to the jumper post behind the battery.

Check the connections on the various temp sensors/switches. There is a different sensor for the gauge than the ecm or fan control. Some cars have as many as 4 or 5 temp sensors. What you see on the dash is not always what the ECM is seeing.

 

[vernh]

Thank you. I will do that. I hope it works. I was starting to consider the idea of possibly replacing the sensor that turns on my aux fan with one that cAme on at a lower temp if the made it and tie both fans grounds to that one switch.

The key to C4 electrical is the GROUNDS. They control everything. Voltage takes a backseat to grounds on these cars. Why? easier to manage/control/less risk. Locate the ground bubdle of 5 wires on a bolt near the oil filter. Clean and repair. Also clean and repair the hot wires to the jumper post behind the battery.Check the connections on the various temp sensors/switches. There is a different sensor for the gauge than the ecm or fan control. Some cars have as many as 4 or 5 temp sensors. What you see on the dash is not always what the ECM is seeing.

 

[John Robinson]

As Boomdriver said the grounds are the life blood of these cars running.




There are no words to describe what strange symptoms and running conditions you will get with bad grounds. Bad grounds have probably sold more high dollar parts that were not needed than any other thing known to man on these cars.

 

[vernh]

Pulled all grounds on front of car and cleaned them. Only one I couldn't find was 103 I have checked all wires for continuity from coolant temp switch back to ECM plug and they check good also checked wires from switch mounted on ac line. Does anyone know where I would find 103 on the diagram? I have looked all over in the area the diagram shows and I cant find that one. Any help would be greatly appreciated. Also has anyone ever replaced their aux fan switch with a new one designed to turn aux fan on at lower temp? I have found one thAt also comes with a new harness to tie into main fan relay ground to turn both fans on at 200 degrees. This way I totally bypass the ECM. If anyone has done this how do you like it?

As Boomdriver said the grounds are the life blood of these cars running. View attachment 4700There are no words to describe what strange symptoms and running conditions you will get with bad grounds. Bad grounds have probably sold more high dollar parts that were not needed than any other thing known to man on these cars.

 

[vetteoz]

has anyone ever replaced their aux fan switch with a new one designed to turn aux fan on at lower temp?
This way I totally bypass the ECM. If anyone has done this how do you like it?

I used this and did my own wiring to save $$
SPAL Fan Accessories - SPAL 195 Degree Thermostat
Have it spliced into original fan control wiring so if switch fails , ECM will still run fan at stock temp

 

[vernh]

Thank you. I am considering doing this because I don't think my ECM is ever telling the fan to come on.

I used this and did my own wiring to save $$SPAL Fan Accessories - SPAL 195 Degree ThermostatHave it spliced into original fan control wiring so if switch fails , ECM will still run fan at stock temp

 

[vetteoz]

I am considering doing this because I don't think my ECM is ever telling the fan to come on.

One last test.
If you are happy fan / relay / wiring is correct , as in you can get fan to run by grounding the Grn/ white on the relay connector
jumper terminals A and B together on the ALDL connector under dash.
That will put ECM into diagnostic mode.
SES light should flash and the main fan should run ( key on )

 

[vernh]

Vetteoz I did jumper a and b terminals. No lights came on and no fans came on. Should car be running or just key on? I did it with just key on. And thanks for all your help

One last test.If you are happy fan / relay / wiring is correct , as in you can get fan to run by grounding the Grn/ white on the relay connectorjumper terminals A and B together on the ALDL connector under dash.That will put ECM into diagnostic mode.SES light should flash and the main fan should run ( key on )