I'm looking for a lower than stock coolant fan switch for the 91 RS w/ 305. Something like described at http://www.thirdgen.org/cool Problem is all the threads I have found on the subject are old. At least old enough that many of the part numbers have changed. Does anyone have more relevant data that is still current regarding part numbers for different sources for coolant fan switches. This thread http://www.thirdgen.org/techboard/tp...itch-part.html (Coolant Fan Switch Part Number for 1989 TPI) Gave me a lot of different manufacturer part numbers but many are outdated or there is no data regarding heat range. Thanks again for any help.

I put a Hypertech Fan switch in my car and if i remember correctly it turns the fans on at 195* as opposed to 225* from the factory. I got it from Summit. Having the fan switch and a 180* t-stat makes my car run perfectly even sitting in traffic in the hottest weather.

Summit and Jegs carry a Jet part #60600 fan switch that turns the fan on at 195-200. You may also want to change the thermostat to a Stewart EMP-301, 180 degree thermostat.

I tried many of them, and gave up on them all - I could never get one to work for more than a few months.

I went with a separate fan controller for my fan, fully adjustable, with options for always on switches in the cabin - cost about $90, and it probes the radiator for sensing. Haven't had any issues since I installed it.

Flexilite

Well today I out in a 180 degree stat and a second coolant fan switch. I used the one for the 87 Grand National since it has a lower temp range. Got everything switched out and buttoned and still a no go. Fan will not turn on when the coolant gets hot enough. I know the fan works as well as the relay, fusable link and the wiring to the switch but for some reason the switch will not trip the fan on. I'm running out of ideas here. At this point I'm pretty much going to go with the Hayden switch from Pep boys like described above and bypass the factory setup. Very annoying!!

One fan, or 2?

1 fan. NOT supposed to be ECU controlled from what i have gathered otherwise that would open up other options as to what may be wrong. There is only one wire running to and from the switch.

If it's only has one fan then it has to be ECM controlled, I could be wrong, but i can't see your sig, so I don't know what you have.
In any case, basics and common sense aside, my answers are third gen based.
Your userID suggest a 94. If, that's true and you are correct on how it works then the only way I can help you is for you to provide the correct diagram because I only have AllData access to thirdgen cars specifically my '88.

See sig below but just to expand...in this case it's th 91 RS with a 305 and TBI. Everything I remember reading on here suggest that the fan switch for my application is not ECM/ ECU controlled. However it is in fact ECU controlled then something like a bad temp sending unit (next to the stat) that the ECU uses to determine temp and send the signal to turn on the fan could be my problem. The sending unit on this car is the original piece so it may very well have gone bad.

If it only has a 1-wire sensor it's a switch. At this point I'd really need a diagram, just to verify what circuit it using. I'm sure it's the same as my '88.

The ECM in Diag mode (KOEO and ALDL connector pins A&B jumpered ) should cause the fan relay to energies.

Yup one wire, it's a switch.

Is the fan on your 88 ECM controlled? Your last sentence completely lost me. I have no idea what KOEO and ALDL are or how to get the car into diagnostic mode.

ALDL is the diagnostic connector under the dash where the troubles codes are read. KOEO is Key On Engine Off.

My primary fan is ECM controlled and the secondary uses a switch like yours, but is in the right side head below the #6 & #8 plugs

So if that's just a switch where is the coolant temperature sensor, in the radiator?

if you do give up, cut the power wire (blk/rd) from the fan relay and run it to the ign slot on the fuse box. Fan(s) will come on when ignition is on. I did this yesterday, for some reason I had to change my gauge fuse to a 20 amp though.

I have the switch on the pass side head between the 6-8 cylinders like you do to drive my one and only fan. The coolent temp sensor is in the intake manifold right next to the thermostat.


While I'm troubleshooting this fan issue I have actually grounded the wire to the fan switch to the chassis so the fan runs as soon as the ignition is turned on. Same idea you had but a different approach.

Resolution with my cooling issue. I made a new post here: http://www.thirdgen.org/techboard/co...ml#post3817040 (Success!! Fan problem with 305 solved!! (long))

95 C (203 F) fan switch. GM PN 3053190
Napaonline has a switch that cross-references to this number, as well.

That's the switch i am now running. According to the dash gauge the fan is still not coming on until ~230. See my new post for details. I think the ECM is controlling my fan coming on. Not the switch.

I found your other thread...I've posted there. According to the factory manual for 89, the fan is NOT ecm controlled. 91 could be different, but it is doubtful.