cougar20th

Do the 2 cooling fans on the radiator come on at the same time or staggered. Ive got one working & one that doesnt. But before I go looking for a problem I figured I would ask.

Stephen

iTrader: (12)

1 is temp. controlled, other is AC on/off controlled (& possibly high temp controlled as well, I'm not sure).

y84pauloflondon

Like Stephen said, passenger side fan is turned on by a Fan temp switch and the other is turned on with the AC system. And some say that the same AC fan also comes on at Very high temps (like 238*), this I'm not sure about. To help keep my temps down I hooked up a manual flip switch inside my car, to turn it on (2nd Fan) when ever I want...Alot of info that will help You is in other threads ("fan switch", and "Overheating issue") Read post # 17 on "Overheating issue" that may help.

deadbird

On an 88 IROC (assuming TPI, since dual fans are mentioned) the primary (passenger) fan is ECM controlled to turn on at 220°F.

The secondary fan is controlled by the fan switch in the passenger side head and turns on at 238°F.

While I'm not 100% positive of the transition year, in '87, the ECM turned on the primary fan only, when the A/C was on. In '89, the A/C would cause both fans to run.
'88 may, or may not, call for both fans to run with A/C but, as a guess, I would wager they should both run.

IIRC, Wiring color at the fan switch would tell you. Dk green would be a single fan runs with A/C. Grey, both will run.

Either way, under normal operating conditions, the fans don't run at the same time.

cougar20th

Yes the car is a 305 TPI car.

Cool. That helps a bunch. Ive only got one fan kicking in at about 225 & shutting off at 220 or so. Oddly it is the drivers side fan. The passenger fan I have not seen run.

I havent checked if the ac turns the 2nd fan on or not. Havent used the AC in a couple years.

deadbird

That's not 100% definitive, that's just going by what's been stated by others for the fan that usually runs.

I always thought my drivers side fan was the primary on my 87 but, it's been so long since I've rewired it, I forget. It shouldn't make a major difference which runs though, as long as one (the ECM controlled) runs when it should (roughly 220°.. give or take a modest +/- % if going by the factory gauge).

383RAT

I've done some extensive wiring on my 88. Deadbird is correct on his statement. They are staggered on. One via the ECM the other via a thermostatic switch on the passenger side. I had the same thing happen to my car. If you decide to troubleshoot it and would like a little help just message me and i'll tell you what i did to figure out where the fault was.

articwhiteZ

iTrader: (56)

you just want More CFM pulling. to do so with stock parts is easy..

just Piggy back the 2nd fan to the first one.. you do not cut any wires.
just use a splice piggy back and.. up grade the fuse just a tad..

it's easy and works better them GM intended...

you can feel the air at the back of you car moving..

keeps it cool in the summer... kicks on when it's Hot and off when it's cool.

deadbird

That is terrible advice. The fans are also powered direct to the battery and protected with a fusible link, not a standard fuse.

articwhiteZ

iTrader: (56)

it's been 15 years ago i did mine..so i could be wrong about the fuse... have to look and see.. but i can tell you. setting it up to run at the same time. works just fine.. no probs at all..and the fans come on and go off just fine.....and i did not have to Cut any wires..

Reid Fleming

iTrader: (2)

For details, check my signature.

As for same time or staggered, the answer is.....both. Here's the deal. On my car, I have a 200/185 fan switch on the passenger side. At the moment, I have the stock GM chip in the car. Now in this situation, you would think that the passenger fan would come on before the ECM controlled driver side fan. But they both turn on at 200°. So it appears that the passenger won't come on without kicking on the driver side if it's not already on.

Your passenger side fan probably does work. It's ultra rare to get it to turn on with the stock fan switch and the A/C off. The car just won't get that hot, that the stock fan switch turns it on. Especially in NH at this time of the year.

Johngypsy

Ok, this is going to sound a little nuts,,,, but bare with me on this,

The Tpi sys seam to get hot a lot,
Some add a external wire for a Togo switch, some just use a jumper to the start (er) relay or fuel panel area,

Some blow out fan motors and some are just to week to turn like they used to!

Ok, with the 305 Tpi sys motors, only 1 fan will work and turn on, as the 5.7 liter tune ports both should work on together, and that's all years from 87-92 models because of much temps passing threw it,
On a normal daily day, when the 305 reaches temp, 1 fan will come on, when it reaches to 220 plus, the other will kick in,,,, and both will stay on together and some time stay on when your car is also off, but hit the ac button and you have both fans working together even if the car just started up for 1 min,

As the corvette with the same set up and the Iroc z and the z28 all with the L98 motors, will always have both fans on at once, of you have only one on with the 350 motor? Determine if the motor was swaped out for the 350 one, because the computer will think it's only a 305? And there fore kick one on at all times, which will cause the car to get hot!

For example:
If you was to buy a, let's say a hypertec chip for you car, (305) and then you install it, and see that the chip was made so that the cars fan will come on more and more then normal (both) that's because it was designed that way for better power to cool the car, as with a 5.7 chip, both fans will come on, even though it was made so with the factory chip and ecm, but with the chip only much more then normal,

So, if you want more cooling car conditions if your in traffic? Don't flip on the ac button while parked and waiting,,, lol,,,, you will need to go the other direction, but to flip it on the heater mode and sweat it out until you can get to a safe location, but sometimes if the regular fan won't come on at all? Then flip the ac button on to get be 2nd fan on, just so you won't break anything in the motor, (heads) (intake) or gaskets, best bet, slick into the other fan for dual all at once, just like the other guys here said, so what ever you have to, so it won't break the cars internals, just remember...... Heat is the number one enemy in a cars life, the heat will destroy a cars life as the motor, trans, and inside of a car, always carry a bottle of water at al times until you can take care of it at your convinces,

And last, if you do a toggle which? Just be careful, as they will never last and 40% of them ALL, fail at some point, it's nkt been made like that, so the factory fans will not last and then will ether completely shut down, or ether just move beyond slow that will never cool down the radiator at all,

Hope this helped all of our 3rd gen readers out there!
John
Iroc z parts and supplies
Houston tx,