over heating issues

Good Morning All, I know this may well be like flogging a dead horse but I am hoping for a bit of advice. So when the car gets up to 180 degrees isn't the low speed fans supposed to come on? I am getting nothing from either side. The Fans do come on at what I am guessing is the high speed side when the AC is turned on. I have researched this problem and from what I can make out is that the resistor has probably gone bad. So I replaced one of the resistors with a 100w, 0.5ohm green resistor off of Ebay. A few you tube channels said this would probably fix the fault. It has not made a difference to the Low speed (?) still only one speed when the AC is on. Before I change out the resistor on the other fan I was wondering if there was a fan speed module or something like that? Or has the motor gone bad? Which I think not because it works with the AC. Any thoughts would be greatly appreciated. Thanks Guys, Knobby.

If you are willing to play with the relays under the dash, you cold also use a jumper wire to test the fans. I can post how to do this when I get home.

The fans run on low speed when the AC is running, unless the engine is hot enough to kick on the high speed fans. The resistors are required to run the fans on low speed as they limit the electrical current going to the fans. If both of your fans were running with the AC on (easy to tell by placing your hand in front of the front tires to feel the blowing air) then you replaced a good resistor. I would not use an aftermarket resistor for this application... they run very hot and an improper resistor could cause other issues. I do not remember the exact temps where the low speed and high speed fans are activated but it is definitely NOT 180 degrees F. I think it is more like 103 C and 107 C for the low and high speed fans, respectively. Use the HVAC system to get a better idea of your exact coolant temp. The dash temp gauge is not very accurate... If both of your fans are operating then the fan motors are probably good. When the fans run on high, it is easy to tell as they are so loud that you can hear them from inside the car. Your probably not getting the coolant hot enough for the high speed fan setting to activate. On a warm day, take your car for a drive to get the car up to operating temperature and then let it idle a bit (maybe even give it a little gas to bring the RPMs up a little while idling), the fans should kick on at high speed within a short time. I'll bet your high speed setting is fine, its usually blown resistors that prevent the fans from running on low speed that is the problem. Also, why do you think you have an overheating problem? Again, use the HVAC system hack to more accurately monitor your coolant temps.

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Also, if the A/C is under high load it will switch the fans to high speed until the pressures reduce. The point here is the the fans should turn on, low speed, immediately when you turn on the A/C. If you turn on the A/C and the fans don't start immediately - but after a few minutes they do start - it's very likely that the A/C pressure went high (because the fans were not running on low speed) and the high pressure kicked the fans on high speed. There are separate high and low speed relays for each fan, and separate fuses for each fan. Two fuses and four relays.

Located under the dash drivers side.

The dash gauge that might indicate 180F could be quite far from what the DME is actually seeing. I once thought I had a problem, too, because my low speed fans do not come on until my dash gauge indicates right at the final white line, which would appear WAY too hot. But it�s actually close to 100C, which is really just fine. My car is a 1999 C2. When it�s very hot out, the high speed fans will come on with the AC only when the AC needs it, which is when AC fluid pressure is high enough. No, the high speed fans will almost certainly not come on at highway speeds. At highway speeds, there is a lot of air moving through the front radiators.

Yes, what Mike Murphy wrote is all correct - the A/C might switch to high speed when sitting in traffic in the summer but won't need high speed while moving. The A/C runs the radiator fans on low speed no matter what when it's on, even if it's not strictly necessary.

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OK, so you can take a wire and attach it to pin 85 on the relay to the fan. The other end of the wire, all you need to do is to touch it to a metal part of the dash to ground it. This will turn the fan on. You can check the high speed and low speed of both fans this way to check that they are working. The relays are 19, 20, 21 and 22. I see that DBJoe996 posted a diagram of the relay box. Its really easy to access the relays and identify them when you are down there. They are above the fusebox. on the driver's side.

Hi Jim, I have swapped two of the relays over on one side, ie, The low and high side relays on one side, Still only the fans for the AC come on. Nothing when the AC is off and when the car is at idle after reaching operating temp. I will try the relay bypass like you suggested. Thanks for your help.

Thanks theprf, When the AC is turned on the fans start up straight away. The fuses all check out fine and I have swapped over two of the relays going to one side with no difference. I'm not sure how long this problem has been here as I live in Florida and have had the car for just over a year and the AC is nearly always on.

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Have you measured operating temp by reading the DME through an ODBII reader or Durametric? My fans don�t come on at operating temperature either. They come on as a last resort.

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Thanks for your advice. I think it is overheating because the needle will move to the right of center (180) especially when I am in traffic at idle. I have pulled into a parking lot when this is happening and there are no fans running. They do run when I switch on the AC. I'm sorry for my ignorance but I don't know the HVAC Hack . Is there somewhere I can look that up? Thanks again.

I live in Florida as well. As a point of reference, while running or at idle, my fans, with AC off, rarely come on unless outside temp is over 85. Sometimes they will cycle on/off if temps are over 90. They definitely run if the AC is turned on. Just providing a point of reference because there may be nothing wrong with your fans. Make sure your ambient air temp sensor is correctly located in the front bumper holder, as the DME/ECU uses that to determine when to run the fans. I find that coolant temperature has little to do with the fans running, unless your car is running excessively hot. While at normal coolant temperature (between the 8 and 0), my low speed fans do not run.

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I'm afraid I have not as I don't have a Durametric So where is your needle pointing when they do come on?

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I see often the outside temp as over 95, and the needle will go past the (0) on the temp Gauge and still the fans do not kick in.

[QUOTE=jim010;17172815]OK, so you can take a wire and attach it to pin 85 on the relay to the fan. The other end of the wire, all you need to do is to touch it to a metal part of the dash to ground it. This will turn the fan on. You can check the high speed and low speed of both fans this way to check that they are working. The relays are 19, 20, 21 and 22. I see that DBJoe996 posted a diagram of the relay box. Its really easy to access the relays and identify them when you are down there. They are above the fusebox. on the driver's side.[/ Thanks again Jim. I will try and do this sometime today and let you know what I find out.

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Right...same here. Just make sure the radiator fans work on low speed and high speed, then let the DME/ECU handle the rest. Check your coolant level and monitor the temp gauge. Sometimes when the ambient temp is over 95 and I'm running (not idle), all fans will come on including the engine compartment fan. Car sounds like a hovercraft when pulling into the garage!

The temp gauge is notoriously inaccurate so no need to worry too much about the numbers as long as the light isn't coming on and your levels are ok.

The low speed fans dont even come on to about 212*f. My car wont even get that hot unless im in traffic with an outside temp over 85*. Most base ob2 readers can pull the temp off the dme. Any higher end snap-on or altel shop scanner can activate the fans in high and low. If it is a big concern pay and hour of diagnostic to your local indy. The low speed resistor is cheap off amazon and easy to splice in if needed. There r a ton of threads on the repair if u google it.

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As I have already mentioned in this thread, they come on when the needle points to the final white line on the gauge.

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Yeah, and if ones happens to be on a dusty dirt road, it will spray dust all over one�s clean car.

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If you have an MKI 996, which it looks like you do from your avatar, you can use the HVAC system to display your current coolant temp. It will give you a much more accurate reading than the dash gauge. Here's the procedure: Hold down the recirculating button and the air up button (arrow pointing up) for 5 seconds. Then scroll through the menu choices with the up/down arrows. Coolant temp is item 6c. I think you then press the center vent button to select your choice. The display will then show your current coolant temp until you press the "Auto" button to exit this display. You can keep the HVAC display on the coolant temp while you drive to monitor your current coolant temp. Here's a link with more info: https://www.6speedonline.com/forums/...-you-know.html See post #6. If your fans run on low speed when you turn on the AC then your resistors are good and I bet your fans are operating on both high and low speeds properly. I would not put too much faith in the dash temp gauge as its pretty inaccurate IMHO. Another thing you can check, if you think you are running hot, is the radiators for dirt and debris. If your radiators have never been cleaned, a lot of dirt can get stuck between the radiators and the AC condensers which requires removal of the front bumper cover to access and clean. You can take a quick peek at your radiators though to make sure there isn't anything obstructing them. I cleaned the radiators on my 996 at about 55,000 miles and while there was some debris between the radiators and condensers, I didn't really notice any improvement in my operating temps after the cleaning. Also, depending on your mileage, a new water pump may help your car run a bit cooler.

You might also unplug and replug the coolant temp sensor on the engine. Sometimes corrosion can build up on the contacts and give higher readings than actual. The Mk1 uses a dual element temperature sensor, one for the DME and one for the gauge - so the DME could be reading accurately and the gauge wrong.

Thank you to all who have been trying to help me sort out this problem. I am sorry that I have been unable to get back to this subject earlier as I had a few things going on at home and I also managed to break my little toe. Apparently trying to arrange furniture with your foot as you walk by is not recommended. As you can imagine I have not been driving the car to much to carry on with a diagnosis. In the last year I have replaced the Water pump and the Thermostat to a 160 from LSN {?) solutions. I guess what was freaking me out was the fact that the needle was going past half way. On all of the cars I have now or in the past the needle doesn't go past the halfway point unless there is a problem. I will be using the HVAC hack to get a better reading as it seems to be a common thought that the Gauge in the car is somewhat in accurate. Thank you all again for the great insight.

Ouch, broken pinky toe hurts like hell!