83 320i 1.8 manual ? about the auxiliary fan not coming on when the temp guage goes past the 12 Oclo

Asked by Feb 05, 2010 at 10:06 PM about the 1983 BMW 3 Series 320i

Question type: Maintenance & Repair

Hello I am new at this so perhaps you could welcome me and give me some tips on how this works. I am happy to find a site like this...... Well I do have a question perhaps someone could take a stab at. I have a 83 320i 5 speed the problem is it runs hot a lot. The temp gauge will go over the half way mark (3/4) to be exact when sitting at a red light or when its hot. Is this normal for the E21's 81-83 for those years? If not please advise me as to what it might be. I have already gone over many things such as coolant flush, new radiator, installed new thermostat cooler Tempature (171F versus the factory 180F thought that would help it did a little). Everything else works great belts, fan, new water pump, wow the car is great no problems other then this one I am naming please advise me thanks.

Also the following below is another post I did when a lot of useful/helpful info that might narrow down the problem with the auxiliary fan not coming on.....
Okay I have done some things to narrow down the problem.
1st let me say this with the engine running when you turn on the A/C the auxiliary fan does come on right away and stay on. So that right there should narrow down quite a bit of things….…. To me that means its not a fuse which leaves us left with 2 things. Either a bad relay or 1 of the 3 sensors is bad. I did pull the relay its looks BRAND NEW AND FINE. However I could not find a fuse or label for a fuse for the auxiliary fan.

These are my questions for you if you could please help me out here with some or all answers. Does anyone know if there is a fuse for the auxiliary fan & if there is one where it is located at? Is there any test I can do to see if the auxiliary fan relay is bad or good? How many fuse boxes are there and where are there locations on my 320i 83 1.8 manual? I only saw 1 fuse box under hood I am guessing that there is others please advise me?

Thanks for any/all help as this problem has been bothering me for some time and I am sure it is quite simple to fix. Everything works on my car its like new. THEREFORE there must be others on this forum or other e21 owners that have had similar problems to mine. Perhaps there it is notorious for the relay or switch to go bad to the auxiliary fan? I also checked the connection where the auxiliary fan connects to the switch I guess which is near the front grill and headlights.

Oh I also looked at all the fuses in the fuse box and they look good none blown that I could tell.

4 Answers


Hello Dave, Although i own an E36 not an E21 i have helped people service some old 5 series too. My mates car seemed to be the exact situation. Running fine and normal temperature other then whilst either stopped and idling or under direct load. We changed almost the entire cooling system(hoses,coolant,radiator, thermostat, water pump) yet it still seemed to overheat. It seemed after a lot of trial and error the way to fix it is as follows. 1. Whilst "cold", remove the reservoir cap (to expel any pressures). 2. Remove the top hose of the radiator. 3. Using a funnel or equivalent, fill the top hose with coolant. 4. Keep filling until coolant comes out the top hose outlet of the radiator. 5. Making sure the correct level of coolant is in the reservoir, replace the top hose. 6. Take it for a spin :) PS. As for the auxiliary fan, it only comes on when the air conditioning is in use. Hope this helps :) Andy

Hello Andy, I am dave thanks for responding back. There seems to be some confusion about as to whether or not the auxiliary fan should come on when the tempature guage goes hot or over the 3/4 mark. I have been told it does come on to cool the car then I have been told like you said it only comes on when the a/c is on. Who is correct there must be a surefire way to know can you advise me thanks. The car is e21 83 320i 1.8 manual


Hello, Yeah.. i once had the same question. I asked on bimmer forums and they agreed that the aux fan only comes on with the A/C. I also asked a BMW mechanic today and they said the same thing. Did you try filling your radiator of coolant from the top hose? This has now worked for 4 cars i have service all having similar issues as you are explaining. I will look for a link to explain everything in detail about the BMW Aux fans, i found it once before.

Hello Andy, Thanks for looking for that link that will help me out a lot I will look for you posting it later thanks. I have not had a chance to try the top hose trick and it will be some time now as we are about to get more snow here:( That means no driving the rear wheel drive cars unless I want to do donuts....:)lol

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