Test if Fan Works?
 

I am in the process of rebuilding my car since my accident, and I started my car for the first time in months :D My radiator fan worked the first day that I turned it on. Two days later, I started my car again and just let it idle, and the fan wouldn't work. My car was actually overheating some, and the fan still didn't work.

Is there a way I can test if the fan works or not? It just seems weird that it would work one day, and not the next. Is there a way I can test if there is some sensor or switch or something that's causing this problem?

Thank you :)

Turn the A/C on and see if the fan comes on. You may have a bad temp switch if it only comes on when the A/C is on. You might also have air in your system which won't allow the coolant to contact the sensor and register the correct temp. I'd start by checking the fan with the A/C turned on and then bleed the air out of the radiator. Make sure it has cooled down before you remove the radiator cap and bleed screw! While bleeding, turn the heater on full blast and add coolant until a steady stream of coolant flows out of the bleeder next to the radiator cap. It helps if you park the car on a hill with the nose elevated. It also helps if you massage the hoses, to push the air trapped in the system to escape. Watch your hands and hair around the belts! Hope this helps, Good Luck.

Thanks. That might be it, I'll look into it!

good info on bleeding the radiator and checking the fan i gotta remember that one

One of the fan sensors is in the passenger side of the radiator.

Pull the plug off the sensor and put a paperclip in the bottom hole and one of the top holes of the plug. This will be either the slow or fast fan speed.

Putting the paperclip in the bottom and the other top hole will be the other fan speed.

This is the most reliable way to check if the fan is operable at both speeds.

I tested the sensor with the paper clip and the fan only works when the paper clip is in one place, and only at the high speed, so would that mean that the sensor in the radiator is bad? Also, the fan doesn't work with the AC on.

http://i135.photobucket.com/albums/q...6/Cimg1568.jpg
When you turned on your air conditioner, did you here it hiss and kick on? Did it blow cold air?

Open up your fuse box. Locate the two yellow relays next to the purple relay. The purple relay is your stage2 fan relay. The yellow relay in the middle is your A/C compressor relay. The yellow relay on the right is your stage1 fan relay. Switch the two yellow relays and see if the fan comes on when you turn the A/C on. They're the same part number so don't worry about messing anything up. Just make sure the car isn't running and the key is out of the ignition when you swap the relays. If your fan comes on after switching the relays and turning the A/C on, you'll know where the problem is.

Okay, I'll check that. Thanks.

Old thread, but no one can say I didn't search!!!

I've having a similar problem.

When I did the paper-clip check, only the high-speed fan came on.
With the car running, turning on the A/C DID make the low-speed fan come on.

Right now I'm chalking this up to the fact that I had to rewire the fan (connector was bad, so I removed it and soldered the connections). It worked well for a while, but the low-speed wiring may have failed. I'll have to wait until I get home to check it.

I've got a new coolant temp sensor on the way, and I'll re-bleed when I install it.

Any other ideas?

I'm having the same problem, just checked. The fan works with a jumper in pin 2 and GND, but not pin 3 and GND. Turned on the A/C, and the fan works. Can't be sure what speed the fan works with the jumper, or the speed it works with the A/C on.

What's next, replace the radiator sensor?

If you tried swaping the low speed relay and the low speed still didn't work when you used a paper clip to jumper around the fan switch (as described by campaiar) the fan switch (temperature sensor) is probably not the problem. The next obvious thing to check is the continuity of the fan low speed resister mounted on the back of the fan.

Excellent first post! You're definitely going to be an asset to the community. Thanks for joining and welcome to the forum!

BTW, I just finished drinking a bottle of tequila and smoking a fat ass stogie, sorry if I sound impaired.

still sounds better than some of the stuff I say :rolleyes:

Is there a part # for the fan resistor/connector? I troubleshot my system, and all the voltages are coming from the circuits/fuses. It's either the relays, or the resistor. I know someone said to swap relays, which I did, but that is not 100% conclusive. First off, what speed does the AC kick the fan on, low or high. I think it uses the high speed, which seems to be working. I can't seem to get the low speed working.

The AC fan should come on at high speed. Perhaps someone else can help with the resistor part number. What I understand is the resistor is located on the back of the fan housing close to the fan motor. It is about 4 inches long and 1/2 inch wide cylinder with two wires coming out the top. The wires run alongside another lead coming from the fan motor to a connector on the bottom corner of the radiator. I'd guess that from underneath the car you could disconnect the connector and measure the continuity of the resistor as well as determine whether voltage is coming to the resistor when the low speed fan should be on.

Did some more troubleshooting. First off, the voltages to both the low speed and high speed relays are there. That is both the triggering voltage, and the main voltage. The high speed relay, in the "un-energized" state passes the voltage to the low speed relay. I pulled out the low speed relay, and put a jumper between pins 6 & 2 (see diagram), and the low speed fan came on. That means the entire fan assembly is good. This was done while I also had a jumper in the temp sensor low speed pins 2 & GND.

Hopefully, that would point to the low speed relay being the problem. When I swapped the AC fan relay, and the low speed relay, the fan did not come on. So either both the fan relay is bad & the low speed relay, or it is not the relay.

I did turn on the A/C, and the high speed fan came on. That would imply the A/C fan relay is good.

Looking at the diagram, it appears the DME sits between the path of the double temperature switch and the actuating function of the low speed relay. This is not the case for the high speed relay, and explains why when I jumper ed pins 1 & GND of the temp switch, the high speed fan came on.

So I can force a connection across pins 2 & 6 of the low speed relay, but I can't get the GND from the DME to actuate the low speed relay properly.

Again, that assumes the relay isn't bad. I only hope the relay IS bad, that would be an easy fix. If not, I must trace the path from pin 2 of the temp switch, through pin 68 of the DME, then out pin 57, and finally to pin 5 of the low speed relay.

Can I get the low speed relay at a parts store, or only at the dealership?

Any thoughts?

http://img502.imageshack.us/img502/9...hematicky0.jpg

My mechanic had mentioned that he thought that even with jumping the fan switch leads for the low speed fan to come on the engine would have to be hot. I don't know what the DME is doing with the input from the radiator switch but perhaps it is integrating another temperature input. Is the engine hot when you are doing your trouble shooting?

No the engine was not hot. Maybe that is why the relay didn't actuate. I still wanna replace the relay, then I'll try warming up the engine.

Related problem:

Summer is at last coming here in Finland. Yesterday I noticed at trafficlights that
engine is warming up a little too much.
I stopped and noticed that I have the double temperature switch at its place, but theres no wire attached?!?

Front end of the car has been rebuilt last autumn. I think mechanic has forgot that wire and cant find it.

Would someone do me a favor, and give me a hint where I should look for it.
I know it comes from DME, but where is that :)

Thanks!

behind the battery is the dme you gotta pull back some foam and you will see the box

With any luck your mechanic put the the wiring harness for the radiatior switch back into place and you won't have to run wires from the DME. The harness should be present under the top brace in front of the radiator and appears to run across the front of the car. It then runs down into the engine compartment with the connector for the radiator switch comming off about 20 cm to the left of the radiator switch and the remainder running down to a connection on a part of the air conditioner. Good luck.

I drove to work yesterday, got stuck in traffic. Temp gauge was climbing, went past the 3/4 point, but not into the red. Traffic started moving, and it calmed down. Can't be sure if the fan came on, sounded like it was but hard to hear.

After testing my system previously, it looks like the fan (high and low) and relays are good. I'm beginning to wonder if the radiator sensor is the problem. I have a new one, will put it in this weekend. I'm hoping the sensor is just not actuating at the correct temperature.

The radiator switch is the first thing to check. It is also important to be sure the system is "burped" so that the switch sensor end is actually in contact with the radiator coolant. You should be able to see if the switch has closed when the engine is hot with an volt/ohm meter or even just a 12V lightblub and some wire.
One caution, I had a local shop replace mine and even though the temperature specs were appropriate (there are two temperature range switches available, mine needed the lower opening variant) the switch they got from their supplier did not open at the specified temperature and was far too slow in opening. If the system otherwise checks out but still doesn't work after you've replaced the radiator switch, it isn't a bad idea to test the replacement in a pan of heated water.
Another tip, If you are overheating in traffic because the low speed fan isn't coming on, turning on the airconditioner should force the high speed fan to come on and the engine should cool down.
However, I thought that you already determined that the fan wouldn't run when you shorted between the switch leads and ground (blk/grn or blk/gry and brn switch connector wires in the diagram above). If the fan won't run when the switch is shorted closed then replacing the switch won't work either.

^^^ air trapped in the system was my problem, with your exact same symptoms (overheating only in traffic, etc)

As you mentioned earlier, the car must be hot in temperature to turn the fan on. Shorting the connector won't trigger the low speed fan unless the car is hot. But even if it is hot, maybe the radiator switch sensor is bad. Or, as someone just mentioned, there is air in the system.

What is the part# of the sensor that turns on at a lower temperature? What are both part#'s, and what are the temp ranges?

How do I burp the system? I know there is a bleeder valve on the side where the fluid level is measured. I was thinking along those lines today. What if the fluid isn't hitting the sensor. The level rises as the car pressurizes, and it still may not be hitting the sensor.

Burping the system is accomplished by removing the bleed screw on the top of the radiator then adding coolant to the overflow reservoir until coolant free of bubbles comes up through the bleed screw orifice. Do this once, drive the car until warm. Let it cool down and repeat Sometimes it takes several tries to completely bleed the system.
The radiator switch is a dual switch and there are two types with different temp ranges. The temperature range is engraved on the switch. I think the part number for the low range switch (80/88 degrees C) is 61 31 8 361 787.

I just did as you described, and the Bentley manual describes it as well. No fluid started coming out of the bleeder valve, even after I fill the reservoir almost to the top. I closed the cap and valve, and drove it around the block. Then I let it cool for a bit, and loosened the bleeder valve. Some air came out, but not much. When I opened the cap, the level had gone down, just below the cold line. I added some more fluid, got it up to temp, and then bled the valve. Gonna take on the highway and hope it's resolved.

Not sure if I'm gonna replace the temp switch on the radiator this weekend, since I would like to know if the bleeding fixed the problem.

My car overheated and some checking shows that the fan is not working.

My 1996 has a two speed electric fan and when I jumper the sensor on the side of the radiator I can get the high speed to run, but not the low speed.

The relays are good (swap) and I am inclined to think it is the low speed resistor mounted on the fan.

Problem is I don't know how to test the resistor and Bavauto does not sell one for 318ti.

Anybody know about these resistors?

Here's the bad-boy I'm talking about:

Read post #16. It explains how to jumper the low speed fan relay, and test the low speed fan. That will tell you if everything is working in the fan.

Yes, I did that. It does not run on low speed.

That is why I suspect the low speed resistor, but I guess everybody just replaces the whole fan unit.

Thanks.

Try disconnecting the resistor and checking for continuity and whether there is voltage coming to the fan when you think the low speed fan should be running. If the resistor is bad maybe you could find one through a junk yard.

A tip on burping. Put the TI's front end on an inclined surface. This helps the air move naturally to the cap of the radiator.

Thats what I am not sure how to do. I have an ohm meter, but the thing has two blue and one black wires coming out of it. One blue goes to the fan. The black and other blue goes to the harness.

I know there is voltage going to the fan even at low speed because it sounds like its trying to turn on when I put the AC on. I can also hear the low speed relay clicking. I am assuming the fan motor is fine because it works on the high speed jump test.

I guess junk yard is the only option besides a new fan unit which is around $300!!

Thanks to everybody trying to help me out.

If I could source these resistors I'd through them out at parades.

From the wiring diagram I'd guess that the low speed fan input would be the black wire. The diagram shows a black wire with a blue stripe. I'd guess that you should have continuity between the blue wire to the fan and to both the blue and black/blue wires going to the harness. I'd expect a higher resistance between the blue to fan wire and the black. I was puzzled by your saying the fan tried to turn on when you turn on the A/C. I thought that the high speed fan should come on when the A/C was turned on.

I tested the black and blue at the plug end of the wires coming from the resistor and its the same reading as when the tester is not hooked up at all. I take that to mean the resister is no good, but I admit I have little experience doing that sort of test.

The low speed setting comes on when you turn the A/C on (even if the engine is not very hot) If the engine gets too hot it switches to high speed.

It sounds like you mean that there is infinite resistance between the black and the blue leads. That does sound like the resistor is bad. I don't know where you can find one new, have your tried calling any of the suppliers or even the dealer?