My fan in my 91RS isnt cooperating with my car... it doesnt turn on all the time... i can have the engine over 220 and it wont turn on, but then 5 mins later, i can have the engine off, and turn the key to ON w/o turning over the engine and the fan will turn on full blast... is this electrical wiring or my prom? either way its really making me mad... every time i stop at a light, my car heats up a good 10 degrees per 1 min @ the light... thats not natural...

 

RS,

That's not generally abnormal with a stock PROM and fan settings. IIRC, the turn-on temp is around 224°F, and maybe a bit higher in the later years, like yours. Our cars were designed to run hot for emissions and fuel efficiency. It's uncomfortably hot for me, so I "adjusted" mine.

The fact that the fan turns on after heat soak is also not unusual, and indicates that the fan, relay, sensor, ECM, and wiring are all functioning correctly.

I see that you've altered your original setup, but what ECM/PROM codc are you using?

 

The fan in your RS is operated by the fanswitch. There are aftermarket F/S' available in different temperature ranges if you want to have it turn on at a lower temp. Also a good idea to get a 180 t-stat to go along with it. Be forwarned, though, with a low temp switch the fan will run alot in warm or hot weather so your fans life expectancy will be shortened.

 

You're probably right. I thought the later TBI setups used an additional ECM output for the fan control. I presumed that is the reason that allowing the ECM's AC Request line to float up high (disconnecting it) is why the fan would operate. I guess I shouldn't presume.

 

im going to try to put a manual switch in my cockpit to solve that... ill just turn the fan on during city driving and turn it off when im on the freeway... and im gunna put a 170 therm in it...

 

Would have been great if they did since it would be alot easier to tweak things. All the outputs that could be used for the fan are tied up by the smog pump crap, though. Pretty much,the fan is only turned on by the HVAC control head or the fan switch.

 

If your going to do it that way, make sure your air dam isnt damaged and the cooling system is up to snuff or itll never stay cool w/o the fan. The way to go would be leave the stock fan switch connected but have the manual switch along side it so you can turn the fan on when you want to.

 

exactly... im going to lower the fan therm, put a 170 in it and add a manual switch... i got lotsa fun in store