Question: Aux fan not working

[gmhowe]

I was told that the fan in front of my radiator for my 85 would come on when the A\C was running, well its not and even the Service Manual or Chiltons does not even reference it all. So beside's fuses what else can I backtrack and find out whats wrong. Its been running about 245 here with the ac on in Phoenix ( been averaging 105-114 here lately )
and can't use my 96 CE since the ac compressor died last week ( crap )

Thanx
Gordon

 

[Schrade]

This is a later C4 fan schematic. Might help you see how to route each fan's circuit through the other fan's circuit, at the two relays on the radiator housing, to confirm that both work.

After that, I don't know where to send ya on it.

My notes are for doing this circuit swap for a problem I had last year...

A few more pics in this thread...
MERGED-(Fresh opti pull pics) & (Ignition stutter-Code crackers needed) - Page 6 - Corvette Forum

 

[vigman]

Fusable links 1988 cooling

Are under the battery... there are 5 or so... they look like rubber tubing ( thick ) moulded onto the red wires.. you need a 12 Volt test light with a SHARP PROBE... test those.. The one that sends power to the Aux fan is link E which goes to the aux fan relay on pin E which is a red wire.

The AUX and the MAIN relay for the cooling fan is located under the master cylinder.

There is a blue wire going to pin D of both relays ( 3 amp fuse in fuse panel ).

This is hot with the key on.. this is the logic for the relay coils..

On the AUX relay this is controled by a Dark green/ white on the drivers side of the block with a temp switch pulling that wire to ground when the temp gets to 228 degrees.. that's the dealio...

To test... 1st try grounding the dark green/white ( Clip lead )

Does the fan kick on??

Does the relay click?

If the relay clicks... go to the Aux fan wiring...

At the fan.. there should be a black ( ground ) and a red black ( 12 volts when the relay closes )

Is there 12 volts there?

If yes... check the black for ground

If the ground is fine... and the Black Red has power.. the Aux fan motor is toast.

If there is no power on the Black/Red.. check that you do have power on the Red wire ( Pin E on the socket ).

If yes on pin E....
The relay is toast


Now see if this jives with your car...


Vig~

 

[vetteoz]

On the AUX relay this is controled by a Dark green/ white on the drivers side of the block with a temp switch pulling that wire to ground when the temp gets to 228 degrees.. The AUX and the MAIN relay for the cooling fan is located under the master cylinder.

'85 has the fan switch between #6 and 8; gauge sensor between #1 and 3 . Switch and gauge sensor positions were swapped in '86 .
And this is the only thing that operates the aux fan, it does not operate with A/c on like main fan .Usual documented operating temp is 235; main fan at 228.

The aux fan relay on early cars is on the front of the radiator shroud, inline with the drv side hood hinge.
There is also a big plug there (heavy red / blk wires ) that you can use to supply power direct to the fan to check if it is working
Could also be something as simple as the switch in head being faulty.
Also , how long since you cleaned out the front of the radiator and flushed coolant? Lottsa crap gets sucked up in the front and the radiator fins get blocked restricting air flow.

 

[vigman]

Good point OZ

1985 is different than 88...
I believe the logic & color codes are the same...

Vig~

 

[vetteoz]

1985 is different than 88...
I believe the logic & color codes are the same...
Vig~

Unfortunately one size doesn't fit all on C4 coolant system controls.:ugh
84 had a mech switch only
85 had ECM control with a mech switch over ride
86-89 had ECM control with mech control of aux fan
90 + had both fans by ECM control

 

[gmhowe]

I was told at the vette shop that the aux fan right behind the front license plate holder was the one that comes on whenever the AC is turned on and the fan behind the radiator in the shroud, right in front of the engine was the main fan that kicked on when temp hit 2xx degrees.
So its my aux fan on my 1985 that is not working
Gordon

 

[gmhowe]

ok I went outside and fired it up, neither fan came on. Turned on the AC and the fan in front of the engine kicked on, fan in front of radiator nuthin.
let it get to 246 degrees fan in front of engine still on but still nuthin from the fan in front of the radiator, so the guys at the vette shop were wrong and the fan in front of the radiator is the main fan that should kick on after 2xx degrees. Which I was more of an electrician to track this stuff down.
Gordon

 

[Schrade]

ok I went outside and fired it up, neither fan came on. Turned on the AC and the fan in front of the engine kicked on, fan in front of radiator nuthin.
let it get to 246 degrees fan in front of engine still on but still nuthin from the fan in front of the radiator, so the guys at the vette shop were wrong and the fan in front of the radiator is the main fan that should kick on after 2xx degrees. Which I was more of an electrician to track this stuff down.
Gordon

You don't have to be an electrician. Electric flow is just like water. It comes from a source, and goes into the sink (ground). In between, the flow gets tapped, to push a water wheel or something, and it goes back into the line to head back for the sink.

Poke a hole in the water hose, and the pressure drops, and the wheel doesn't turn as fast. Plug the sink (bad ground), no flow. Simple.

 

[gmjunkie]

You don't have to be an electrician. Electric flow is just like water. It comes from a source, and goes into the sink (ground). In between, the flow gets tapped, to push a water wheel or something, and it goes back into the line to head back for the sink.

Poke a hole in the water hose, and the pressure drops, and the wheel doesn't turn as fast. Plug the sink (bad ground), no flow. Simple.

Thats a good way of explaining it!!
Just 1 problem I see with it,most plumbers only know 2 things!!
Sh*t won't run up hill and Payday is on Friday!!

 

[gmhowe]

Junk,
You

 

[gmhowe]

Junk,
You are as funny as you are wise.
Gordon

 

[gmjunkie]

Junk,
You are as funny as you are wise.
Gordon

Thanks!! I think??:ugh
"vigman" is purdy right on about the fusible links,I have to replace so many on the 91 back models that I have 3-4 rolls of link different gages in my tool box!!

 

[vigman]

Gordon.. do you have a test light?

It's REALLY easy... I'll walk you through

Vig~

 

[vetteoz]

let it get to 246 degrees fan in front of engine still on but still nuthin from the fan in front of the radiator, ....... the fan in front of the radiator is the main fan

Main fan is BEHIND radiator.All '85's have it and have perfectly adequate cooling with just one fan
Some like yours also have the Aux fan in FRONT of radiator.
Something is wrong with your cooling system; you should not be seeing 246 degrees.
Have you checked the actual true engine temp; gauge may be wrong / faulty

 

[ken mohr]

Main fan is BEHIND radiator.All '85's have it and have perfectly adequate cooling with just one fan
Some like yours also have the Aux fan in FRONT of radiator.
Something is wrong with your cooling system; you should not be seeing 246 degrees.
Have you checked the actual true engine temp; gauge may be wrong / faulty

He is correct. Look for debree in front of your radiator. The main fan should pull the temp down almost instantly.

 

[gmhowe]

Then why does the fan behind the radiator come on when I turn the ac on and turn off when I turn the ac off ? The engine was rebuilt about 3 months ago and just started this hi temp thing where the fan in front of the radiator does not come on at all. and no debri as the radiator was replaced just 18 months ago and I have a screen to stop debri from coming in. I have a chip and the shop just replaced the 180 thermostat with the 160 snice the put back in a 180 during the rebuild. Could there be a problem with the thermostat ?

and Junk that was a compliement

Gordon

 

[ken mohr]

There is a pressure switch in the line that turns on the main fan as soon as the the unit is pressurised. You may have a thermo hanging up. Lets see if anyone has any ideas.

 

[vetteoz]

the fan in front of the radiator does not come on at all.

First up as previously discussed , you need to confirm that
1.the aux fan actually works
2.the relay works
3.the temp switch in the head is operating.

 

[vigman]

Agreed!

The main fan needs to come on either with the A/C or when the car hits 228 ( ish )

the AUX fan only has 1 control which is the sender on the side of the block.

Mid America ( and others ) make a lower temp turn on switch.

if your car is getting up to the 240's you are WAY TO HOT!

My 88 puked it's heads @ 238 ( other issues there )

But when I pulled the radiator.. there was a TON O STUFF trapped between
the A/C condensor & the front of the radiator.

35% of my cooling was gone due to all the road kill the main fan sucked up there.


Vig~