Cooling fans stuck ON?

So my cooling fans are running constantly. As soon as the ignition goes on, the fans go on and stay on.

I understand that the temp sensor for the fans is in the bottom of the radiator, so I unplugged that and they still ran.

I was getting 11.8v at the cooling fan harness, BGB said normal is 5-10 or something.

I am thinking that it is the fan solenoid in the fuse box, stuck in the on position.

Any suggestions? Where can I get a replacement part?

Cooling fans are reverse-wired, so if any of the component fails, they are designed to stay "ON" to help prevent overheating. Carefully check everything along that line.

I have a gremlin in my cooling fan system, I had to hard wire mine to even get it to work. Regardless, I would point my finger at the switch in the fuse box or the sensor in the bottom of the rad. there is a step by step in the bgb to test the relay. If you need a new one I have one still in the box, bought one thinking it was my problem, let me know.

there is also a sensor in the air conditioning hard pipes that will turn the fans on if it's removed or broken.

All Fours":voh21q4k said:

there is also a sensor in the air conditioning hard pipes that will turn the fans on if it's removed or broken.

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since I'm no wiring guru, would there be any way for it to malfunction and not allow the fans to turn on? I'm still trying to figure out whats going on in my car, I have the fan hard wired to a switch and run it constant after it warms up a bit.

I dont have my BGB in front of me, but If I remember correctly the system on the ST185 is wired like the one on my 3rd gen. The temp sensor switch in the bottom of the radiator is normally closed, making a direct signal to ground under normal (cool) conditions. Once the temp increases, it opens, giving no signal (which is the same as pulling the connector off) causing the fans to switch on.

The easiest way to test if the sensor is bad is to run a wire from its pigtail to a ground and see if the fans shut off. The pigtail has only 1 wire in it, right?

If its 2 wire, then you just bridge the 2 together.

It is 2 wire, I tried bridging them and got the same thing.

I am going to try a new solenoid......and if I remember correctly, there was a solenoid sitting around inside the car when I first got it, cant remember what happened to it, and I did buy the car with a bad head gasket....so Im wondering if this problem isnt what caused the car's demise in the first place....dont want that to happen again!!!

Thanks a lot for all your help guys!

Yeah, recently my cooling fan was stuck OFF - it was that little temp. switch on the bottom of the rad... good luck

Slink":1tvvq79s said:

Yeah, recently my cooling fan was stuck OFF - it was that little temp. switch on the bottom of the rad... good luck

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when you unplugged the switch did the fans run constant? Mine didnt, still cant figure out my real issue.

RIalltrac":bwgcrri7 said:

Slink":bwgcrri7 said:

Yeah, recently my cooling fan was stuck OFF - it was that little temp. switch on the bottom of the rad... good luck

Click to expand...

when you unplugged the switch did the fans run constant? Mine didnt, still cant figure out my real issue.

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yep, mine did

Just checked through the wiring diagrams. Just as Rick89GTS said, the fans are wired to run constant if any sensor fails.

The radiator fan relay is normally closed, giving the fans power all the time. The relay's trigger wire (which turns the fans off) is a system ground - which goes through the A/C pressure switch, then a check connector, and then through the water temp switch to ground. This wire is blue / black according to my BGB.

Do you have a digital multimeter to test for voltage and continuity?

So, testing the system from the end of the circuit up:

1. water temp switch - as stated eariler, connect the blue wire to ground or bridge the 2 wires together. Jumping the blue wire to ground is a better option, since bridging the wires assumes that the white wire has a good ground connection. You can check the ground by testing for continuity between the white wire and the negative terminal. You can also check the blue wire for voltage - no voltage means something is dead before this sensor.

2. Check connector. Make sure its connected - See if the blue wire has voltage here. If there is no voltage, then continue on. If you do see a voltage, then make sure the wire is getting to the water temp switch (continuity test). You can also bypass the temp sensor and some wiring here and connect the blue wire to ground.

3. A/C pressure switch. Check for voltage here, or bypass it and connect the blue wire to ground taking the check connector and temp sensor out of the circuit.

4. Radiator fan relay. If everything above has passed, then it could be a bad relay. Just like before, you can bypass the whole circuit by connecting the blue wire at the relay to ground. This should cause the relay to "click" and the power to the fans should stop.

Have fun!

lol fun, thats a good one. I hate wiring, its like my arch nemesis. I must have spent like 3 hours hovering over my engine bay checking wires and what have you trying to figure this out. Its too damn cold out nowadays to get into it, but I'll be using your tips above come spring time to resume my search.

Sweet!

Ive ruled out # 1 and 4 I think.

Now- I yanked the AC out of my car....so I think this may be the problem. I do not know where ther check connector is or the AC pressure switch.

I'll see if I can look them up in my BGB, where they used to be. I can ground the wires that are left over and see if I can get this working right.

Thanks again!

If you have removed AC then this is almost certainly your problem:

3. A/C pressure switch. Check for voltage here, or bypass it and connect the blue wire to ground taking the check connector and temp sensor out of the circuit.

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The pressure switch is on the AC hardpipes just before they enter the firewall. It will probably be on the passenger side (my car is RHD so it's different). Chances are you unplugged the sensor and binned it, but there should be a black, 4 wire plug around that area.

There is one other place to check for a fault. I thought I posted this before but maybe not. Behind the glove box there are two little computers in black housings. I dont know the proper names for them, but the lower one controls the fans. I had the problenm of my fans running constantly and I studied the diagrams like, forever until I found that computer. I switched it with the one from my parts car and the fans have worked perfectly ever since. good luck!

Cool, thanks for all your help!

Ill look into later today, let you know what I find.

And the winner is!.......

four wire connector where AC line used to be. Yaaaah!

And your consulation prize is the enjoyment of not having two worry about overheating when standing still.

I put a jumper across two of the wires and fans instantly worked properly.

Note to others who are removing their AC!

Thanks again guys!

good now that you've fixed your issue now you can help me fix mine

k_trac":246s31xb said:

And the winner is!.......

four wire connector where AC line used to be. Yaaaah!

And your consulation prize is the enjoyment of not having two worry about overheating when standing still.

I put a jumper across two of the wires and fans instantly worked properly.

Note to others who are removing their AC!

Thanks again guys!

Click to expand...

Which two wires did you jump??? (color)

I have tried this before and it did not work for me!!

Thanks
Dave

Here it is, Ill check on the color or the wires, but you should be able to tell by looking at this pic.

Just try jumping them, and see what works.