My understanding is that the auxiliary fan in front of the A/C (radiator) can't remember what you call it is supposed to come on whenever the A/C is on. I've had trouble with cooling in town and found out today when checking the system that it's not on. I'm guessing it's dead, but I haven't had time to check the electrical yet.

I'm looking for suggestions. Do these go awway often? Are there common electrical checks, problems or solutions, what shouled I check first besides the connection at the fan side? What should I expect to pay for a replacement? Replacement proceedure? In the Generals wisdom they have chosen to D/C this item. Where's the best place to get one? Thanks for any help, nothing really on search.
:lol:


[Modified by 86Moon, 6:47 PM 4/25/2003]

 

CHECK AT CONNECTION IF YOU ARE GETTING 12 VOLTS D.C. WHEN AC IS TURNED ON, IF YOU ARE THEN CHANGE FAN SUGGEST LOOKING ON E-BAY SEARCH PUT IN CORVETTE FAN. IF THERE IS NOT 12 VOLTS PROBLEM IS ELSEWHERE.POSSIBLY THE RELAY---THERE IS A WAY TO PUT JUMPER IN RELAY TO TELL IF IT IS FAN OR RELAY I JUST DON'T REMEMBER EXACTLY HOW.

 

Thanks, found fan on ebay, new $44. It should come on automaticly with A/C right? Do you happen to know where the relay is? Haven't checked for electrics yet.

 

The main fan is controlled by the ECM, and is comanded on when A/C is selected on.
It's my understanding that the aux fan is controlled solely by the aux fan temperature switch in the left head between cylinders 1 & 3. The fan should turn on when the water temp reaches 228*F. You might want to take the connector off and put a jumper on it to ground, and turn the ignition to run. That should turn the fan on. If the fan runs then you have a bad temp switch.
If the fan doesn't turn on, place a jumper between the red wire (should have 12 vdc), and the black and red wire at the relay. This will direct battery voltage directly to the fan. Be careful, because the red wire is hot at all times. If the fan turns on replace the relay. If the fan is still dead, replace it. Hopefully it's just a $5 temp sensor and not the fan.

 

You should have 2 fans, a main which is on the engine side of the radiator. It will come on about I think 215. It will also come on when a/c is on. The relay is on the left fender well. If you ground the sending located at the left front cyl head the fan will come. The aux fan is on the condensor side of the rad, it comes I think around 235 and the relay for it is under a plastic cover near the left head light. Hope this helps.......... :cheers:

 

As stated the aux fan (in front of the radiator) is controlled ONLY by the aux fan switch in the block below #1 & #3 spark plugs. Turn the ignition On and jumper that wire to ground and you should hear the aux fan come on.

Remove the shroud over your radiator and clean the debris from between the radiator and the A/C condenser to help with cooling.

Also you can install a lower temp thermostat and aux fan switch and wire that switch to control both fans, per my C4 Tech Tip.

 

:confused: Sorry got my wires crossed.... 65Z01 is correct....


:cheers:

 

Wow, OK. I don’t know if I posed the question in a confused way or what, but there seems to be a lot of conflicting responses here. I tried to read and understand them last night and I gave up, couldn’t do it. I thought it was the beer, but when I looked again today I still was confused, so here goes.

85autoxr, I’m sorry but I don’t understand the procedure you’re talking about.

Fast Glass “The main fan is controlled by the ECM, and is comanded on when A/C is selected on.”

I dunno, but I think the aux fan is supposed to come on with the A/C switch, not the main fan.

“You might want to take the connector off and put a jumper on it to ground, and turn the ignition to run. That should turn the fan on. If the fan runs then you have a bad temp switch.”

OK, I grounded this and the fan came on, This means the switch (sensor) is bad? From what I can determine this is the case, it may have just been worded in a way that was difficult for me to digest.

Mike's 86, " The relay is on the left fender well. If you ground the sending located at the left front cyl head the fan will come. The aux fan is on the condensor side of the rad, it comes I think around 235 and the relay for it is under a plastic cover near the left head light."

This is really confusing and I know you said you reversed something later.

But, my understanding is: the AUX fan should come on when the A/C is activated, period, continuously. Is this wrong? The relay for the aux fan is near the headlight. Right? It clicks when the fan comes on. Based on my understanding 235 has nothing to do with any of this.

65Z01, "As stated the aux fan (in front of the radiator) is controlled ONLY by the aux fan switch in the block below #1 & #3 spark plugs. Turn the ignition On and jumper that wire to ground and you should hear the aux fan come on."

YUPPER, I guess, so here’s my problem, and hopefully final question here: I really can’t read schematics. I have buddies who can in the business, but sometimes they know more than they do and don’t want to take the time to go through the whole deal. I can’t blame them.

Here’s the problem: The AUX fan DOES NOT come on PERIOD. I’ve run the engine through the entire warm up. The main fan comes on after the initial area I think at 195 or so, then runs up to 220 or so and cycles between there and 195-200 I think. The Aux fan never comes on.

Here’s the question: Should the Aux fan come on with the A/C SWITCH, if so does that mean that I need to replace the sensor in the block between #1 & #3?
If so, this is apparently controlled though the ECM?

I think that the answer to both is yes, and I know it’s here, but I want to be sure
:confused:

Thanks for the clarification anyone, sorry to be so longwinded :smash:

 

It is easier to understand seeing the wiring diagram than trying to have someone explain it.
The main fan on the rear of the radiator is controlled by the ECM, and will come on when A/C is comanded on.

The aux fan on the forward side of the radiator, the relay is in the left headlight bucket, and it is only controlled by a temp sensor in the left head between cylinders 1 and 3 to come on at 228*F. It WILL NOT come on when A/C is comanded on.

You said that when you took the connector off the switch between cyl. 1 and 3 and grounded it with the ign in run the aux fan came on? If it did, replace that temp switch.

By grounding that out you set the relay which in turn will send power to the aux fan. When the fan turns on you know that the fan is good, and that the relay is good, and that the wiring between all that is good.

keep asking away if your still confused. I'm not the best explainer, I do better showing.

 

Here’s the question: Should the Aux fan come on with the A/C SWITCH, if so does that mean that I need to replace the sensor in the block between #1 & #3?
If so, this is apparently controlled though the ECM?

I think that the answer to both is yes, and I know it’s here, but I want to be sure

As mentioned, the aux fan (in front of the radiator) is only controlled by the aux fan switch. Your test showed that fan & relay are OK. The sensor is likely ok as it only turns the fan on at high temps. If you want that fan to come on at lower temps replace the stock aux fan sensor with a lower temp sensor. HyperTech makes such sensors and are available through Summit Racing. Be sure to match the new sensor temp to that of your current thermostat.

Now, if you pull the A/C pressure plug (on the right side in the A/C coolant line) and start the engine the main fan will come on, but not the aux fan. When you pull this plug it opens the circuit to the ECM and simulates high pressure in the A/C coolant line. So the ECM turns on the main fan to reduce that pressure.

Botton line: those two fans are controlled independently of each other.

 

Fast Glass,
You've done a fine job explaining. The problem is he has gotten so many conflicting answers, his head is spinning. Fast Glass's explanation is spot on, expect for the turn on temp and relay location. If the switch is stock, it won't close until @240°F, the manual is wrong. In stock trim, it's pretty darn hard to get this fan to come on. If pushed really hard for a long time, like high rpms at low speeds for extended periods, you may see it come on. I see mine come on at track days for instance. The location of the relay on mine is as shown here: .

 

Didn't know the manual was wrong - Scanning my '89 has the aux fan coming on at 228. Main at 226 unless a/c head pressure is about 233psi on the manifold gauge set, a/c on of course. Since repairing a leaking head gasket, replacing the radiator, flushing all of the crap out of the system, & rebuilding the a/c, temps never get high enough anymore to turn on the aux fan. I had to verify the temp by checking in an enclosed garage, a/c off & the main fan disconnected. Switches are available for a lower turn on temp, though you shouldn't need one if system is functioning properly and with the extra draw of both fans running on a charging system that is marginal at best, fans may not maintain maximum rpm with an extended idle; hence, temps climb back up as fan speed goes down.

 

Looks like I'm learning too. My aux fan isn't factory, so that explains the different location. Plus mine comes on right around what the book says so I figured that was the correct temp. Maybe it was easier for the replacement kits to come with lower switches to match the book than to reprint the book. :)
Sorry if I lead you astray anywhere.

 

Wow, thanks for all the help guys :cheers: . But I don't think I'm quite home yet :rolleyes: . I apparently had the fan opperation mixed up. The big problem is NO FAN comes on with my A/C. I thought the aux was supposed to com on. Now I ran the car up to 225 in the garage at about 65-70 degrees. The main fan came on and off with the thermostat as I think it should. I think I said that already. Never got to 228 so I guess I'll have to check the aux when it's hotter.

Going to reread cause I know you're trying to explain it. (This is one of the PITA's on this forum, You can't review all posts when replying in the thread- never seen that before).

65Z01, I found the switch you're referring to on the High side line, the smaller of two right next to each other, unplugged it and started the car, the fan came on. Ilet it run for 2-3 min and plugged it back in. The fan went off after about 15 sec or so.

[U]I guess I still need to figure out why the main fan is not turning on with the A/C.
[U]

[Modified by 86Moon, 8:33 PM 4/27/2003]


[Modified by 86Moon, 8:55 PM 4/27/2003]


[Modified by 86Moon, 8:58 PM 4/27/2003]

 

Didn't get close to 240. Now as for the manual being wrong (maybe I don't need one), The relay is on the other side of what you're vey nice diagram shows. http://@forus.com/moonunit/Corvette/...an%20relay.JPG http://@forus.com/moonunit/Corvette/Fan%20relay.JPG
It's the one with the red cylicone on it.


[Modified by 86Moon, 8:43 PM 4/27/2003]

 

Dammit Jim---- I'll never get this right. I can't figure out how to post two links on a page with out getting them merged into one. Here's the second one with the cylicone :mad . http://@forus.com/moonunit/Corvette/Fan%20relay.JPG
Anyway I still can't read schematics. I have access to them, but it's too time consuming to get my friend to read them and help me truoble shoot when his shp is busy. Thanks again everyone for your help :yesnod:

 

The aux fan doesnt come on at all when the a/c is on...think of it as a back up fan in case the car OVERHEATS.The single main fan in front of the radiator comes on when the a/c is on,or the temps reach 220-228.Since yours is working fine,the aux fan will never come on since theres no overheating.
You can wire the aux fan to come one the same time as the Main fan if you splice into the main fan relay.Not necessary since I did this and didnt see much change in temps,just more fan noise while theyre both running.

Now,if your MAIN fan doesnt come on when the a/c is turned on,you may be low on freon,the switch on the pressure line is bad or the ecm is bad and not commanding that function,but still works when the car reaches warmed up temps.

 

That's a strange location for the Aux Fan Relay. I'm fairly sure the coupes and convertibles had them in the same location. It's very possible it was added later. Does your RPO list on the inside lid of the storage compartment or console show B4P? It's also likely that there is a difference between early and late production '86 locations. From the other's posts, this is probably more likely, but check for B4P anyway, just for grins.
At any rate what you've learned is the Aux Fan is controlled only be the Temp Switch in the head and has no connection to the ECM or A/C. The stock '86 switch will close @240°F. For testing purposes, you can disconnect the main fan and see what temp it comes on at. Don't let it get above 245 in the event the switch is bad. The rest of the circuit is tested as you already have, grounding the connector that goes on the switch.
As already stated, your refrigerant charge is most likely low causing the main fan not to come on with the A/C. By disconnecting the High Side Pressure Switch, you tested the A/C command to the ECM and that worked. You now need to have your gas charge checked. It's most likely low never getting to 233PSI when the compressor is on. This is all assuming your A/C is working! The Compressor Clutch does engage the Compressor, right? If your charge is really low, you'll have no A/C because the Low Side Switch will not allow the Clutch to energize, so no Compressor run and no High Side pressure build up and no Main Fan. So let's get that clear.
Once this is all done and working, do as also suggested earlier, clean the debris between the Radiator and Condenser. Even with the Main Fan on when it should be, if it can't draw enough air through the Condenser/Radiator sandwich, your temps will rise.
Good Luck.

 

A/C line pressure is related to outside air temp or temp of the air flowing through the condensor. The fan switch opens & turns the fan on at about 233psi and then closes at about 190 psi, turning off the fan. On cooler days, pressures will be lower and the fan will not cycle as much. 50 degrees or less, the fan may only cycle once in awhile. To test, without a manifold gauge set, wait for a 70 degree or better day. The fan should cycle constantly, with very little off time, on a fully charged system at 70 degrees or better. If it doesn't, get a gauge set or go to an a/c shop for a pressure check.

 

Oh man, I'm starting to feel like I'm a "brick". Ya'll are talking at times in terms that I don't understand. I'm working with "real tools" here. The A/C testing equipment works on temps more than pressures as I understand it. Look, my main fan should come on wit the A/C being activated. Right. It isn't. My A/C is comming on. It's not cycling frequently. It blows COLD 34-36 degrees at idle in 70 degree outside temps when the main fan comes on. There's a good charge in the system. It sucks sitting in traffic cause the fan isn't comming on. The main fan doesn't come on when I activate the A/C Oh ya. I replaced the radiator 4 mos ago. Cleaned the whole area spic and span. There is little or nothing between the radiators. THE MAIN FAN DOEW NOT COME ON WITH THE A/C ACTIVATION. This is the problem I'm trying to solve. Whoa, I'm tired. I know you're trying to help, but I guess I'm not expressing myself well :nonod: Thanks everyone :banghead: