Hi Speed Fan not working?
You need to double check your 50 or 60 amp fuse, whatever your system has. Physically remove it, then test it with a multi tester for contiinuity. You also need to disconnect your fan wire connecter and clean out the terminals with an electrical spray cleaner and wire brush. We had the same problem that you are having. We were blowing our 60 amp fuses one after another. Same thing happens, only the low speed fan will come on. When the ac is turned on the high speed fan is suppose to kick in, it didn't. We disconnected the fan wire connector, cleaned out the teminal pins with an electrical contact spray and small wire brush. You may want to test the low and high speed sides of the fan while you have the wire connector disconnected. Run jumper wires straight from the battery to do this. Check the wire diagrams above to see which system you have, so you know which wires are the postives and negative. If both the low and the high side of the fan works, then you can look elsewhere for your problem. We then installed a 60 amp breaker in place of the fuse. This was over two years ago. So far, no more problems with the fan circuit. Both fans come on when they are suppose to. The Constant Control Relay Module in the picture that someone provided, does not have anything to do with the 02 sensors. It only supports the fan and fuel circuits. It's a multi type relay system. On the early models, I believe it is under the driver seat, on the later models it's under the passenger side fender, between the fender, and fender well, just above the strut housing. I believe your 02 sensor problem is another matter. This Constant Control Relay Module, is not your main Computer. Your main Computer is located elsewhere. Good luck, Tommy.
