I have an 88 IROC 350 TPI and am having some cooling issues with it. Car runs fine when actually cruising, but in traffic (stop/go), the temp climbs to 240/250. I have the dual electric fan setup, and the only fan that ever comes on is the drivers side fan at 240 degrees. First, which is the primary and which is the secondary fan. I have not been able to find a certain answer: some say drivers side, some say passenger side. Both fans have a black wire and a black with red stripe wire. Also, haven't been able to find a straight answer on which are the fan relays and which one is which. I have three relays on my driver's side firewall (two have an oval shaped top, the other is square shaped). Need to figure out this cooling issue. Thanx

 

That's probably due to it changing.

If you've searched (or just read the few post on the current first page), you''ll know where the fan switch is. Key on, unplug and ground the fan switch wire. The fan that runs, is you secondary. Unplug the fan and ground the fan switch (with helper) and you can locate the relay (probably on the passenger side near the radiator). Could also be that if you have a SD TPI, the two relays are fans. The square is likely to be fuel pump.

Keep in mind, ecm fan on temp is 220° and fan switch is 238°. The accuracy of the gauge can be +/-20° (not fact) but, that's another topic.

 

Ok, so I replaced two relays: one by the radiator and one by the battery the other fan now comes on. However, both fans push air back over the engine (Not forward through the radiator to the front of the car). Is this correct? My car is actually running hotter now with both fans going. If the fans are supposed to blow forward, how do I fix that? Thanx

 

So (at least according to my in dash temp gauge), BOTH fans come on at 240. The passenger side stays on for a little while then shuts off. The drivers side stays on longer, then shuts off when the temp comes back down. What the heck is goin on here?

 

The primary fan is the one that is front of the driver seat. The secondary is the one on the passenger side.

A stock fan switch will rarely turn the secondary fan on. Our cars just don't run that hot (especially this time of year) for very long.

The fans are supposed to suck air from the front of the car and blow it over the engine. You'd be fighting natural airflow when you're moving if they didn't. Fans only run at less than 40 mph. So the idea of radiator fans is to take up the slack when you're driving slow enough that natural air movement up from the air dam into the radiator isn't enough to cool the vehicle.

Best bet is to buy a fan switch that turns on at 200°/off at 185°. Could also get a new chip that programs the fan to come on at a lower temp.

 

So as I mentioned, both fans come on when my temp gauge reads 240: then the passenger side one shuts down at 230 and the other one around 220. Now, is the primary fan only controlled by the computer (which gets its temp readings from the sensor in the intake manifold)? And the secondary fan is controlled by the sensor in the passenger side head? Now, I have read that the temp gauges are often off. Is this a defect in the gauge itself, or a problem with the temp sensor in the driver side head? Thanks for your help folks

 

Tolerances in the production of the gauge, made in china replacement sending units, age, wiring deterioration. There are a lot of factors that can cause the gauge to lose it accuracy after 17 to 27 years.

 

Bottom line up front? there is a problem with your temperature guage. The Primary fan (the Black with Red stripe) is designed to come on at 228* F, the secondary (black with pink stripe) at 238* F. The guage builds up resistance inside in the wiring; crud, dust, etc get in there and make it harder to move. Someone takes the dash apart and messes with the needle- they will come off and there is no meas to index them so that they go back on properly. The wiring in the F-bodies are notorious for developing corrosion in the "weathertight" connectors- which throws off the guage as well.

The primary fan is controlled by the computer via several feeds from components in the car (the sensor in the head, the A/C pressure switch). The secondary fan is controlled by a Temp switch (which actuates at 238* F) on the passenger side of the block. The location of these switches varies slightly by year- but I have always seen them here. To get to it you will have to be under the car- look slightly below and to the rear of the motor mount. Be careful, there is coolant behind the switch. One more note- DO NOT use thread tape, shellac, etc on these types of sensors- that will prevent them from working properly.

The best thing you can to to help the engine is to use an aftermarket fan controller. GM set the temp for the fans to come on high- this helps with combustion, but is not exactly friendly for engine wear. You can pick up an aftermarket control system for the fans that will use a probe in the radiator fins and eliminate the entire stock system AND will control 2 fans. They will also actuate the fans for the A/C- it only requires connection of a wire to the A/C. The bonus to these- they are adjustable! You can custom set the fans to the point YOU want them to come on- it only takes a few minutes with a screwdriver.

The radiator fins get damaged, crap gets caught between the radiator and the A/C Condenser, the Air dam gets damaged and/or broken off. Modifications to the engine, engine running lean... ALL of these can cause trouble with overheating. The biggest problem that I have seen with F-bodies- people build the motor, and don't build the cooling system EVENLY to match. Using a morepowerful waterpump (higher flow) alone will not help. Upgrade the stock P.O.S. radiator to at least 3 cores- I personally used a champion MC-951 4 core that I got on Ebay for $300. I can run the A/C on a 95* day sitting in traffic and not move above 190*- and my motor is pushing a little over 350 RWHP.

If anyone needs the schematics- I have the GM service manual. They are a h*ll of alot better than anything I have seen anywhere else, AND they have ALL of the schematics, not just the ones that Haynes and Chilton choose.

 

So I'm leaning towards installing an aftermarket fan controller for my dual fan system. Is there any reason I need to leave the fans hooked up to the factory system/relays, or would it be fine just to have it being run by the aftermarket controller? Also, anyone have any recommendations on the brand of controller (flex a lite vs. Hayden for example)? Thanks for all your help