Hey guys I have a question. I was checking my cooling system the other day and I noticed the little fan in front of the radiator does not come on. I was told this comes on when you are at a red light and running the A/C.
First let me explain something. I have put a new radiator, new themostate, new hoses new heater core new A/C system, (compressor, reciever dryer, lines and it is running a R12 system.) I also changed all the fan relays as well. The car runs cool but I notice on hot days in heavy traffic the temp will shoot up to 235 degrees although it does come back down to about 210 to 215.

I have experimented in the garage with the car running at idle I watch the temp go up to 228 and the big fan kicks in and cools the car right down, when I look up under the front of the car I noitice the little fan does not kick on. So I turned on the A/C and let it run and heat up with the A/C on but it never comes on.

I do have the Helms book and I went through it tonight but all it says is how to remove and replace and trouble shoot the big fan,I dont have a problem with the big fan. Does anyone have any ideas ????

 

Booster fan comes on at 238

 

Oh, and the AC only turns on the main fan. The Aux fan is controlled soley by the temp switch in driver side head.

 

Aux. fan is only controlled by a temperature switch in the head, it doesnt come on by any ECM control.

 

Vader take it slow for me , are you saying that if the temp exceeds 238 then the little fan will come on?
The reason I ask is because I have been told that it comes on when you are in heavy traffic but no one has ever explained to me how it works other than that

 

Is that a typo or is the 86 different from the 88 by 10 degrees? The 88 FSM says 228*F (109*C) for the 88 Aux. Fan, page 8A-31-1. The main fan should come on 2 degrees before that, at 226*F (108*C) OR when the A/C coolant fan switch closes at 240psi.

In GM's odd way of defining things under the hood, the "Coolant Fan Temperature Switch" is not for the main fan, but is actually for the Aux. Fan, and as AGENT86 pointed out, it is the sole controlling device for the aux. fan.

If the aux. (booster) fan isn't coming on at 228*F give or take 2 degrees, I'd check the fan relay and the coolant fan temp switch. On the 88 most of the relays are the same, so an MAF relay or the manual transmission OD relay can be swapped in to do a quick check of the aux. fan relay.

The coolant fan temp switch should close (0 OHMS) when heated to 228*F or above. The switch should have one green/white wire going into it where it is located in the driver side head between the 1st & 3rd cylinder. You can easily test it by removing the wire where it is attached to the switch by a plastic clip, and grounding it to the block. When you turn the ignition on, the aux fan should run. If not, you have a bad relay, an open in the wires to the fan, an open Fusible Link E,or a bad aux fan motor. Most likely the relay or the switch.

 

Couple more things, the main fan relay is located on the wheel well just in front of the battery, and the aux. fan relay is next to the radiator, drivers side. You can buy a lower temp switch for the aux. fan (mines an on 200, off 185) and wire them in such a fashion both fans come on at the same time...without having to reprogram the ECM. Mines been like this for 6 years. I think there might even be a "tech tip" write up on it.

 

 

Hey guys I think i found the problem, After carfull insoection I noticed the wire going to my switch in the block had come off. So I reconnected it. I also notice that the little plastic piece was broken that goes into the switch. I hate to replace the whole fan assembly for this little problem, Is there anyone who has an old fan that i can have that green wire with the plastic piece on the end?

That way i thought I would splice it in and the problem would be fixed.

 

I picked up mine at our local jobber in this little town of 10,000. The same connector/pigtail is used on the knock sensor also.

 

Steel Breeze, like warrior2291, you have an 88 also as I recall. The 88 FSM page 8A-31-1 says 228*F (109*C), for the 88 Aux. Fan. NOT 238.

 

There are at least 3 different quoted temperatures in the 86 manual for the fans.

The only one that is correct is that listed at 238F

 

My aux. fan would not run, even with jumpering it. I removed it and without it blocking airflow to the radiator, run several degrees cooler at cruise. (5-8ish)

 

Well, if the 86 FSM has 3 different temps quoted, then WHY would someone who owns an 88 want to use information from an 86 manual that has obvious errors? Given that the original question was concerning an 88 and not an 86, why not use the info from the manual that is correct for his model year Vette?

Unlike the 86 manual, the 88 FSM consistently states the main fan is on at 226*F in 4 different places. Pages 6E3-A-8, 6E3-C12-1, 6E3-C12-2, 6E3-C12-4. That being the case, I'd say that the 88 FSM is:
A) not inconsistent like the 86 FSM, i.e. more likely correct
B) the appropriate and accurate manual for an 88, for which the question was asked.

As posted, the 88 FSM says the Aux. fan is on at 228*F. What happens on an 86 is obviously anyone's guess, since you state that the 86 manual is not consistent. I'll take your word on the 238*F for an 86, but I am interested in why you picked 238*F from the 3 choices in the 86 manual.

 

Ok guys so far you have been a big help to me. I went back to my Helms book and you are right the big fan comes on at 228. Thats the one the sits in fornt of the engine..I found my problem with that one I need to replace the wire comming out of the harness that goes the switch in the block. Apparently the little plasitc piece on the wire broke off and it does not sit or plug in very tight to the switch. i repaired that temporarly with some duck tape until i can find the green wire that comes out of the fan harness and splice a new one in. I really dont want to but the whole assembly just for that. So if anyone has any idea I am open to sugestions.

What I wanted to really know was when does the small fan come on in front of the Condensor? I have ran the car in the garage and when it gets to 228 without the A/C running the biig fan comes on at 228. When I start all over again( Let it cool down) and turn the car on again and let it warm up again if I turn the A/C on the big fan kicks on immediately. I never see the litte fan come on?? I have been all through the helms book for my 1988 but I have not seen anything on the little fan in front of the concensor.

 

Its quite simple, I dont have an 88 manual and theres no a priori reason to assume they would change it. Why would GM turn on both fans at 228? Theres no reason to do so.

I know from being here that the MAIN fan for all years comes on a 228. That IS stated clearly in the 86 manual.

1. Yes 86 does say the MAIN fan comes on at 228.
2. If only 88 owners replied to all questions concerning 88, then do you think this question wouldve been answered? I guess you never answer any question regarding any other year besides 88 right?

So does the 86 manual in one place, and its wrong, that would be why I picked the other one to be right after seeing it activate there. What part of that wouldnt be blatantly obvious?

Of course we know that GM is the all-knowing all-seeing Goliath that never made a single mistake in all the years of C4 production and their manuals are the holy grail of everything.

 

You need to jumper the connector to see if it even works.
If Mike's 88 manual page quotation is correct, you should see the temperature in the manual listed.

Otherwise take it out and make it heat up to 238 and see if the auxiliary fan triggers.

 

thanks vader i will do that tonight and let you know

 

The specs - 226 main and 228 aux - are right for your Year and you can double check the Main by using a scanner because it's signal is from the Coolant Temp Sensor. Have the a/c off, because with it on, the ECM will ground the Main Relay when the high side gets to about 220 - 240 psi, regardless of Coolant Temp. You need a manifold gage set to check that out and since you've rebuilt the a/c, maybe you have one? If so, and given your temps, it wouldn't be a bad idea to look at your pressures and see what the high side is doing. Frankly, the Aux fan should rarely if ever come on. It was a 100 Buck moneymaker for GM and plenty of Vettes left the Factory without it and cooled just fine with a single fan (and obviously, since it isn't tied into a/c, it was never intended to have anything to do with it's operation). I never saw the Aux fan temp when my 89 was new - and I don't now - though I never turn off the a/c. My guess would be that it's overcharged or there is something else going on. Can't imagine great vent temps if your coolant temp at idle is anywhere near 238 degrees and you might also want to look at your alternator output as if it's that warm, it's probably on battery voltage. That will slow your main fan down and once that happens, temps climb - AND if the aux comes on, that's just a bigger drain and if both fans aren't up to speed, they're not doing what they should be doing - cooling it down. Solution is to get it to cool right with the single fan - overcharged a/c - plugged orifice - low alternator output (probably the Achilles Heel and difficult to overcome with the stocker) - would be suspect given all that you've replaced, assuming the cooling system is tight and nice and clean. Other problems would perhaps be a plugged tranny cooler or dirty filter (assuming it's an auto) - leaking head gasket.

 

Just to let you know the A/C is right on the money and everything in the system is brand new including the condensor the radiator, the reciever dryer the orfice tube the line ......the compressor.......AND the ALTERNATOR, the battery, the intake gaskets, all the fan relays the mass air flow sensor.......get the picture!....sooo with that said i am leaning toa new temp switch...and to repalce that wire too.........