My primary cooling fan circuitry died last summer and I was told that fixing it would be a very expensive venture. I am getting increasingly more annoyed as days go by of having to turn the primary fan on with the little switch I had installed (plus, forgetting about leaving it on has cost be a battery). I just recently got a new radiator, so my cooling system is ready to be made new again. I want to go with a 160 thermostat and respective low-temp fan switches. Will a new fan switch solve my primary fan problem, or will I have to replace something before the fan can be automatic again? Also, the secondary works, but by the time it comes on (my current thermostat is stuck open) my coolant is already at 230-240 degrees (ouch). Can this all be done, and for how much? Thanks.

 

It's about $16 from Autozone.

 

How do you currently have the fan wired? Were you grounding the relay or just feeding 12 volts to the fan motor directly? If you were grounding the relay the suspect the CTS. Rarely does the ECM driver fail unless direct 12 volts is fed to it when the driver is on. If you are feeding 12 volts through a switch to the motor change the relay for starters. The easiest way to diagnose the pri is to jump the ALDL connector like you are going to retrieve codes. During code retrieval the pri fan self tests and will run automatically during the entire time the jumper is in. With this method you don't have to run the risk of overheating the engine. Find the primary fan relay, in 89 it's behind the rad on the pass side all by itself. Jump the ALDL then have someone turn on the key, hold the relay in you hand and see if you can feel it energize. If it energizes but the fan won't run replace it. Remember, if you have a dual fan system all you have to do is turn on the aux fan with a temp lower than the temp that the stock comes on and they will both run. The ECM defaults automatically if it sees a low on the aux control input from the fan sw before it turns on the primary, usually at 220-225 degrees. Forget about all that extra garbage and wiring, you don't need it.

 

When I had it checked out over the summer, my mechanic had mentioned that he believed it was an ECM problem and that would cost me about $345 to fix (a bit pricey just to get a fan working). However, I currently have the primary running off of one of the 12 volt auxiliary slots on my fuse box, which runs to the power line on the relay, and then the other end of the switch goes to a ground right under the center console. I am guessing since he didnt need to bypass the relay that it is still good. In the event that this is an ECM-related problem, what would be my best bet about fixing it? I am guessing that trick with the auxiliary fan temp would be the best bet?