Alright i bought this fan switch off of jason D and went to install it today. After wireing everything up correctly and triple checking it all, there was still problems. First off. It wasnt working. I flipped the switch, and nothing happened other than one LED would flash for a split second as soon as i switched it. Thats it. So i get out the little stick that checks if you have power to something. Well what i came to the conclusion of, was the wire that i was directed to use as a ground wire, actually had power to it. I dont know if something was wired wrong with the switch or what? Anyways, what ended up happening was one of the LEDS blew up, so i cut the power wire and ground wire to it, and pitched it. I connected the ground wire to a bolt/metal piece on my shifter and went ahead and wired everything up like that. What i ended up with is one LED light that comes on for both, hi and low fan settings, A switch that works, a car that hasnt burnt down yet, and an SES light. So what is causing my SES light? Any ideas to you know it alls? Well thanks in adanve and ill take another shot for you all.

 

More than likely you are grounding the fan relay control line which is pulled low by the PCM when it wants to turn on the fan. This has the same effect as the PCM by grounding one side of the relay causing it to close and turning on the fan.

However, the PCM monitors its control lines to see that they are at the proper state prior to the PCM changing it to ground.

To put it in other terms, one side of the relay coil is tied to the fan fuse #7 under hood where it gets 12 volts all the time. The other side of the relay coil is connected to the PCM. Before the PCM takes its side to ground, it checks to see if 12 volts is there. IF it is not there, it sets a fan code.

Since you are probably grounding this line with the switch, the PCM is seeing that it is not at 12 volts when it checks and sets the SES.

What you need to do is use a couple of resistors as in Robs diagram (thanks Rob) to prevent the problem.

http://shbox.com/1/fan_sw_diagram2.jpg

 

So is this something that will cause more of a problem than an SES light? Such as shorting out or blowing fuses? Also, if it is just a SES light, when i have my pcm tuned could i have the code deleted? Or would it just continue to come on. Thanks for the good answeres though, and the link. You guys are great

 

I would fix it, so that it works correctly. That way, if you have a real problem with the fan wiring, the PCM will tell you. If all you are getting is a P1641 or P1642, it won't really hurt anything else that I know of.

 

Thanks shoebox. Ill try to hunt down some resistors to get it fixed, but wanted to make sure its ok to drive for now. I havent had the codes pulled to even see what they are but will check it out as well. Thanks again to everyone