Cooling Fan wont come on over heating!!

ASSISTANCE Stock Engine-Bay Components
1

So I just got a new thermostat put in my car thinking that that would solve my overheating problem. It helped alittle but at a stop light the oil temp gauge goes up? but when I am driving it is at about half way. My question is what should I test first? I tested the cooling fan relay and when it is disconnected I tested the two power terminals for continuity and it gives me a volt reading of like 103? Is that right? or should I not get a reading when the relay is disconnected from the battery? I also disconnected the terminal for the relay and the fan works fine when jumped by a battery? I dont know what I should do next, any advice?

2

I’m assuming you mean that at a stop light that your coolant temp gauge goes up, not your oil temp gauge… but what year is your car? If its a '92-'93 I would suggest checking your temostat-housing-mounted fan switch. Mine went bad causing my fans to not turn on and in turn my car would overheat if the car wasn’t moving. On the highways it was fine. Replaced the fan switch and all was gravy.

I don’t know a whole lot about the voltages of relays and stuff though, maybe someone. Else has more input on that. Do a search here with the keyword Overheat… seems like there has been more and more people overheating lately… probably because of it being summer, meaning hotter temps.

3

My car is a 91 LS and It has a temp guage but maybe im all over the board with my questions. The cooling fan should kick on before the temp guage goes past half way im assuming? Im just trying to pinpoint the problem so I dont have to replace a bunch of different things that it could possibley be.I will try to test that thermostate housing switch and see if thats the problem. Thanks any other advice or links to pinpoint the problem would be helpful.

4

I just had the same problem last week replace your temp switch it’s on the passenger side of your head

5

Thanks I will try that and see if thats the problem. Is it pretty typical that one of those would go out? Any other advice would be appreciated hopefully I can narrow it down.

6

So I tested the continuity for the cooling fan relay. I am getting 103.4 VDC. The car is off but Im still hooked up to the battery. My manual says that there should be no continiuity? is my relay bad or?!? please help:bawl:

7

i love it when people tell others to change parts based on what fixed their problem in which could have multiple possible solutions.

yeah. that voltage is high. you sure the multimeter is ranged correctly? not reading mV?
you have ac? you can try using your ac fan relay. see if that works. your relay may be shorting internally

8

ya my cooling fan doesnt come on either but i dont think it makes a huge difference just as long as theres proper circulation through the radiator core. someone correct me if im wrong but my cars been my dd for over a year and ive never heard the fan come on and its never overheated until just recently but thats because of a leak. I’m thinking about wiring a switch to my fan so i can turn it on and off whenever i want but i’m not too confident in my wiring.

9

…or you could just fix the problem.
your fan pulls air through the rad, cooling the antifreeze inside it. so yeah, it’s vital. specifically at idle

10

So last night I just had to keep trying stuff to diagnos the issue and I noticed some antifreeze leaking from what looks like a big rivet?that is connected to the head were the coolant comes into the head?!? but the thing is that its not leaking from the threads its leaking from where u would hook up a like a grease gun. I know that that is not what thats for, grease that is, but maybe thats were an a/c recharger would hook up? any ideas as to why and what that might be happening?

11

thanks welfare for the advice. And your right about the multiple things that could cause a problem. I also tested the relay completley disconnected and I was still getting a reading of 103.4V with the ohm meter set to continuity. Shouldnt it read OFL with it completely disconnected?

12

A couple things:

  1. When you check for continuity, you should be checking it with the wires to the switch unplugged so there shouldn’t be voltage there. Either you get the “beep” or nothing. Also, if that 103.4 is not a typo (you’ve written it twice) then you aren’t reading your meter correctly or it is broken.

  2. Are you talking about your coolant bleeder nipple? If there is a significant amount of air in your cooling system, the thermo switch will not operate properly and your fans will not come on.

EDIT: Actually, yeah, do you know about bleeding the coolant system? I think that little bugger is 8mm? May be 10.

This is how I do it, I’m not sure it is the 100% correct way to do it, but it seems to work fine for me.

  1. Make sure car is cold enough that you can open the radiator cap without burning yourself with steam or coolant. Turn the heat on in the car (but don’t turn on the fan) so water can circulate through your heater core too.
  2. Open the radiator cap and start your car (with cap still off). If the radiator is totally full, you may get a little coolant that spills out.
  3. Wait until the car is at operating temperature. 10 min or so? …until your thermostat actually opens up so water is flowing through the block. Keep the radiator topped off.
  4. Open that little bleeder valve just a little bit so that coolant kind of spills out of it, if there is air in your system, it will sputter and kind of spit coolant out.
  5. If you open that valve too much, air will get in behind the threads and make it seem like there is air when there isn’t.
  6. When you are getting a steady stream of water (or if the coolant starts to swell out of the radiator cap), close the bleeder valve (it doesn’t have to be super tight to close all the way, you don’t want to strip anything out).
  7. Close your radiator cap after making sure that you have coolant in your overflow reservoir and the radiator is full.

I don’t know about a 91 LS, but on a 92-93, that sensor should have between 200-300Ohms between the terminals at normal operating temperature.

13

I was having the same issues a couple weeks ago, turned out to be the ground on the front driver side, I took it off sanded down the paint and it works fine now. Worth a shot.

14

Thanks for the advice. I went to a shop of a guy I know and he said to switch out the ect switch and the cooling fan sensor. So I did and it solved the problem. I bled the system and added coolant and it is running below half way now. No wonder the fan wasnt kicking on. Thanks again to the people that added to this post.