Having resolved my recent cooling issues (namely my bad waterpump and radiator), I have arrived at the problem of my fan not working. I've already tested it according to the method set out by 91Z28-350 in this post: https://www.thirdgen.org/techbb2/sho...hreadid=283556

It has been a number of months since I ran all these tests, but having done them it pointed to a bad fan switch, which I have since replaced with a lower temp switch. However, it still doesn't turn on. I'm gonna recheck it once I have some more time, likely on Sunday. In the meantime, does anyone have any idea as to why my fan wouldn't work if the motor is good, the switch is new and the relay gets power in the correct places? Any ideas would be greatly appreciated, as I have no idea where to start...

Thanks everyone.

 

check your coolant tempature sensor.It only takes about 5 minutes to change and they only cost like $8.

 

Man that write-up seemed like an awful lot of work, just to diagnose a bad relay, and/or bad wiring. (Reminds me of a Mitchell-On-Demand diagnostics)

With Key On, Engine Off, turn HVAC controls to Max a/c cold. Fan should turn on. If this does not work, take the fan switch connector off, and ground it to, say like the frame, with KOEO, fan should turn on. IF this also fails, smack the relay...I know that sounds silly, but sometimes the relay's wiring comes apart inside. Obviously if the fan comes on after you hit the relay, you have just diagnosed a bad relay. lol

Check back with what you have found out.

 

Well, I spent some time working on it the other day, replace the relay, reconnected some wires the previous owner had spliced elsewhere, and now the fan works when I turn the A/C to on, though the A/C has been removed. The fan does not seem to come on by itself, with the A/C switch at off. I'm not very confused, as I've spent alot of time tracing wires and comparing them to the wiring diagram, but I still cannot figure out why it doesn't work properly. But at least it works when I want it to now...

 

The factory fan switches for these cars don't allow the fan to come on until the temp is somewhere around 225º. Now factor in the factory gauge, that is usually around 20º off (high or low)..your fan might not come on until the gauge reads 245º or higher.
Here's a link for some fan switch options

 

Yeah, I probably should have mentioned that I changed the fan switch as well. It's a 195 on 180 off I believe. So it definately should have come on pretty quickly. Also, is there any way to make the stock gauge more accurate? I'd like to know the engine temp, but I don't really want an external gauges. Thanks for your input.

 

I apologize, you did mention the replacement switch, I just had a brain fart. Take the connector off the fan switch, ground it out somewhere with the key on, engine off. Fan should turn on. When I did this, I put my trusy old code scanner (paper clip) into the connector and touched it to the frame rail. Fan turned on, well I did have to wiggle the paper clip around a little...
If this makes the fan come on, then it is definetely a problem with the switch.

 

Yeah, if i ground the wire to the switch, it comes on. It does not come on at all with the engine running. If I turn the "A/C" on, it turns on, regardless of temp. I guess the new switch I bought is bad then?

 

Yeah I thought that with mine at first too. But it would come on, but by the time it did, the gauge was reading over 250º!!! You didn't by chance buy another factory replacement switch, did you?It was summer, so what I did was just bolt the wire to the frame, so the fan would run whenever the key was in the 'on' position. After that, I used a T/A fog light switch, ran wires to it, and made it into a manual fan switch. Looks totally stock, except I don't have fog lights. lol
Well, it's neat watching the indicator light come on by itself when the fan comes on, either by the new 185º switch, or from the A/C.

I ordered the one in that link I posted. The one for like $21.00. Seems to be working fine for me, but right now my fan switch is in the thermostat housing (from a carbed v-8), because I forgot to take the plug out of the pass head in the L05 when I installed it

 

I bought a 195 on 185 off switch. I've run the engine to up to the top hatch mark (not the red one). Unless my gague is off by like 50* it should have come on. I ran it for like 15 mintues today, with the fan toggled on. So I guess I'll just leave it as a "manual" switch until I feel like ordering a new switch.

 

sorry to interupt your thread, but this is related.

My car was doing the same thing (fan only comes on when A/C is on or I ground out fan switch, all problems point to broken switch). I replaced my switch a week ago, thinking this would fix it, but it didn't. but if the engine is hot and i jump the connector to say the head where it positivly grounds out for a second, the fan will kick on and work. did i get a bad swicth or what?

thanks

 

I had the same problem with my new fan switch. After installing it the fan still did not come on but I can pull the wire off and use a paperclip to ground it on the car and the fan comes on. I wonder If I used too much teflon tape on the threads. Tomorrow if get time I am going to try the test again and touch the wire to the side of the switch. To see if the switch is getting ground.

 

I'm making efforts to ground at the A/C switch on the PASS side along the fender, rather then drain any fluids on the block. The thing is, prior to my fuel pump and leaking radiator, the fans worked in the past. When they exactly failed is beyond me, but after putting in a replacement radiator, not having the aid of the fans is making running for any length of time a challenge

I had the above plug undone and then grounded....does it need to be attached AND grounded? I ran the A/C in all positions, but with the car off, then the engine running... I didn't notice the fans start up at all

I'd hate to replace everything currently, as I'm virtually broke
Bill

 

For the past 5 months I have been trying to figure out my fan switch problem. I know the right switch in standard ts 136 I believe. I installed it but it had the thread sealer on it (red ****). Ran it up to almost over heating and nothing. I think some of these switches are not grounding out properly. So what might work is next time one of you pulls out a fan switch run the old engine brush through the hole. the only one the worked for me was the one from r+s straus it came on at 240 and came down to 220. Granted I change the original temp sender to a standard switch. Which may be why some of your gauges are off. But any way a friend of mine suggested wrapping a wire around the switch while its in the car and running the other end directly to the negative terminal on the battery. This will tell you if its a bad ground or the switch.

It seems like alot of us are having the same problem...... I just want the original setup to work the way it was designed. If I ground that wire anywhere fan comes on. So which switchs are working and which are not. And by the way if you install a switch and it has goup on it wire brush that **** off.... Plus if you want to test the switch take a hanger wrap it around the switch. Run a wire around the the thread like 3or for times run it to a multi meter then run a wire from the regular connector hook them up to the old multi meter. Get a thermometer and drop the base of it that would be in the coolant in the boiling water ........... and see when she comes on temp wise that will tell you if the switch is working.

Unfortunatly I lost the on at 220 off at 200 switch I was gonna test it but it went in the coolant bucket...... and never saw it since
please let me know what you guy's come up with. I got everything running great except that stupid fan.............