cooling fans wont turn off

[Xraller]

I have a 99 beetle and the radiator cooling fans wont turn of even when the key is off and out. They keep running till the battery dies. I have checked all the related fuses. Any ideas?

[Xraller]

an update - I have checked the coolant temperature sensor. Trying to get to the coolant fan switch sensor. Hope that is it other wise it is some computer chip and that seems like that would be expensive.

[dav97236]

When the coolant fan thermoswitch goes bad it defaults to the closed run all the time position which is better then the open never run overheat until head gasket blows position.

[Xraller]

the coolant fan thermoswitch is the one that is on the side of the radiator yes?

[dav97236]

yes lower driver side of rad

[Xraller]

Well I don't think it is the thermo switch. There are some exposed wires that were touching each other and even a little sparks and flames when I connected the battery back up.



The thermo switch might be bad because of the shorts but first I'm going to get everything seperated, fix any bad wires and then see what happens.

[dav97236]

Now here's the next thing to keep an eye open for. This car has a amp spiking problem in this curcuit caused when both fans are running with a/c on and one fan momentarily hangs up for a second . This curcuit is protected by a 30 amp green fuse located in the fuse block mounted on top of the battery. There are three of these and the one to look at is the one closest to the engine or #1. The problem is the pins that hold the fuse are small and will/can arch and burn that area of the fuse block without blowing that fuse causing an area of high electrical resistance . Meaning 12 volts on one side and like 6.5 volts on the other side of the fuse which will tell fan control module to enter sleep mode and make a/c compressor not work and cooling fans to not operate at all. The reason I am telling you this is that the amp spike on your vehicle seams to have found it's weak link in your thermo wiring and once repaired maybe on look out for next weak link which is most commonly that fuse area. If this happens let me know I have a good repair for this without buying a new fuse block.

[danielsatur]

If you had an old bug, you wouldn't be having a problem!

[Xraller]

I agree about that. But its my wifes car. Its the car she had to have. Now I get to say I told you so about the reliability.

[Xraller]

Ok....got the wires fixed and still had the problems so I replaced the thermo switch and that fixed it....although not right away. When I first plugged in the new switch was still the same problem. So I started to investigate how the switches worked by heating them up and checking the resistance and comparing the two. After heating up the new one I heard it 'click' . Plugged it back in and it fixed the problem. So I'm not totally convinced it is a good one.

@dav97236 - I will be watching for the problem you described. But my working theory is some battery acid leaked down onto the wires and ate away at the affected wires. We bought the car used an I cant tell the battery has been replaced a few times.

[dav97236]

Yes that sounds quite possible. Looking at the picture it does not look as if the wires were rubbing together so it could of been acid eating the wire covering. Not a very good idea locating any control module under battery tray but, this car was designed in Germany , built in Mexico, for Americans to drive. lol . Remember the thermistor changes resistance, the hotter it gets the less resistance allowing current to flow turning on the fans so checking it against the bad one may not give a logical result. These are not bad cars they just all have the same typical problems and once fixed they go for a long time. I bought a 1999 beetle for a commuter car 6 months ago fixed all these problems and it's runs great and is very reliable still at 177,000 miles. Saves me about $75 week in gas over my expedition. good luck