I have a single electric cooling fan, and it keeps acting up. I just replaced the fan swith not to long ago with a 170* switch, I believe. I was just sittin there with my car running at idle while I'm getting the carb all adjusted and noticed the fan wasn't running at all so I jumped in the drivers seat and the temp was at 220 and I also had like my vent on. When I pushed the rod from vent to off and then back to vent the fan kicked on for a second but then died off so I put it on bi-level and the fan was running. Not sure if fan is suppose to run when you have it on vent but I swear it did before. Well anyways I pulled the rod back to see if the fan would just stay going but no luck on that. Whats the diagnosis for my cars sickness... I almost thinks its the fan switch but want some second opinions, I'm going to check the wires to the switch and make sure its all good tomorrow. Later guys.



Vetter

 

You have a bad fan relay. The fan switch controls a relay that is also controlled by the A/C. In vent only the fan should not run until it gets to fan sw temp. Not sure where it is on the 91, they are either located on the driver side firewall in the engine compartment or near the rad. It's very common for them to act intermittent. Don't get an aftermarket, they suffer from the same design problem the originals had. GM has an updated part, so does NAPA. Should cost about 20 bucks either or. Part of what contributes to premature failure of the relay is a low temp fan switch. It cycles the fan constantly and unneccessarily I might add. There is no reason on earth to run the fan at 170, it places undue stress on the alt, the fan motor and the relay. Up to you on that one, NAPA has one that's on at 215 and off at around 185 or so. Might be a better choice.