1988 350 IROC - There is what looks like a temp/fan switch near the #8 spark plug - I believe it is a single wire - anyone familiar with part/part number ? I believe this controls the second fan. Also not a cooling question but what is your opinon on using a Battery tender ? Any potential damage to computer? Any problems with battery fumes ? The battery IS NOT sealed - should I remove the cap(s)? I also have a heater core to replace which I have been prolonging for a while. Thanks !!

The part is a cooling fan switch:

http://www.autozone.com/autozone/cat...&parentId=63-0

Shouldn't have any issues with a battery tender - they only charge 1 or 2 amps at a time, and they start/stop as needed. I wouldn't think caps need taken off since it only runs 1 or 2 amps - when charging witha real charger, your running 10 or better charging amps, which can build up fumes from the acid heating up and become an issue, but shouldn't with a little tender.

Could you please outline a troubleshooting method to confirm this is the issue. Should fan spin when car is first started up and then shut off? Again this is the secondary fan. Are there any otther sensors that should be looked at? Thanks for your help

If you turn on the AC and the fan goes on, the relay is good. All the switch does is ground the wire when the set temp is reached. With key on grounding that wire should turn on the fan. If that all works and you still get no fan when the engine is heated up it's the fan switch

I dont believe I see the secondary fan spins when the AC is turned on or when the car reaches upper temp. The primary fan appears to be functioning propery. Your thoughts?

First thing check wiring connector to the fan for good contacts and then put 12 volts directly to the fan to make sure it is working. If that's all good check the fan relay. Both the AC switch and the fan switch provide a ground to the green with white stripe wire at the relay. You can try grounding it there which will eliminate or point to wiring problems to that point or possibly expose relay pigtail weaknesses. If testing while the car is not running(good idea) you can swap out the relay next to it for the fuel pump to test with.They are the same