electrical and ignition Electric Fan Turning Off Too Soon In This Summer Heat!

[enoklite]

Hey all!

 

Driving around lately in this L.A. weather has been taking its toll on my poor 02's cooling system. I have an electric fan kit installed right now by one of the previous owners, but it seems to only want to come on once my coolant temp is at around 75-80% and turns off when its still around 65%. These percentages usually happen on days like today where it was near 90 deg. out. Obviously, the ideal set up would trigger the fan at much lower temps.

Might I have a problem with the fan's relay or thermostat? Any ideas? If i'm leaving out anything let me know!

 

Thanks!

[M3M3]

get a fan switch with a different range.

 

you did not provide any info at all about exactly what you have in there now.

[jrhone]

LOTS of things to check.  How is the coolant level?  What is the coolant mix?  Old or new coolant?  Where is the fan switch?  What type?  What temp is it set at?  What brand parts?  Factory BMW?  Pep Boys specials?  That sounds like my initial setup.  I replaced it with a factory BMW switch and it all works perfectly.  Comes on just a tad over half way, turns off under half way.  Pics and details of the install are key.  This can be done a number of ways so we need to see your setup.  

[jimk]

Don't panic!  It may be high to your liking, but it won't kill the car because the fan is cooling sufficiently.  If the temp stayed up then there isn't enough fan and it is not cooling sufficiently.  Look at where it is sensing the temp also and choose a lower temp switch.

[jrhone]

Oh another thing....how are the grounds on the gauges?  Are u sure the temp gauge is reading accurately?  I had bad grounds and did the ground mod of the gauge cluster and that changed the readings on the gauges...they were reading too high.  Here is a test...when you turn on the lights, do the needles jump?  Mine used to...after the ground mod, they dont move when the lights turn on.  What fan are u using?  I am using a high speed SPAL.  I had no issues in 118 degree heat in AZ.  85-90mph on the freeway in 120 degree heat and the car was at half way on the temp gauge....I was much hotter inside the car...lol..

[RayC911]

I would just try a 71 Tstat and install a manual toggle switch too

[enoklite]

Thanks to everyone for the excellent replies! My coolant level was fine--not completely topped off (which I did today) but certainly not low. It would seem then that the thermostat controlling the fan is allowing it to turn on late.

However, as has been pointed out, I may need to check the gauge ground(s). When any of the turn signals are flashing, the temp needle bounces ever so slightly. With the headlights toggled on, it rises slightly as well. It may be that the car is cooling off at adequate temperatures but the temp needle is just not accurate due to poor grounding.

I think I'll have to use an IR thermometer and see what my actual temps are next.

[jrhone]

Where is your temp switch?  in the radiator?  Water neck?  You never said what temp switch you had in there...

[enoklite]

Mine is located in the radiator, but I cannot discern a temperature range from it as it has no markings.

[jrhone]

This may be your problem....I have mine in the water neck where the temp gauge gets its temp.  There are water necks out there with multiple ports for various sensors.  There is a heated debate about what works, but I just looked at mine in the garage...it comes on at just over halfway and goes off and just under halfway....keeps the temp at halfway.  You could also have a bad temp switch.

 

Here is my water neck..the fan switch on on the right...temp gauge sender is on the left.  I'm actually going to be going with a 3 port water neck so I can install a sender for my VDO water temp gauge I just installed.  I went this way so in the future, I don't have to modify a radiator so my car works.  If Im on a road trip and need a radiator, I can get a stock one and bolt it up.  Its a stock BMW fan switch so I can get one anywhere BMW parts are available.  

 

[jrhone]

Others may chime in that have more knowledge, but after thinking about this here are some questions...

 

1. Your fan switch is on the radiator...so its monitoring the temp AFTER the coolant is cooled....your temp switch is monitoring the temp of the coolant BEFORE its being cooled.  so in between the switch and the temp sensor is a thermostat, radiator, engine.  You have to account for all those things when you are figuring out what temp the coolant needs to be at when the fan turns on.  What happens when the t-stat is not working properly?  How does that affect the coolant temp?  How about a radiator that has a slow flow?  

 

2. If the radiator is clogged, the coolant stays in the radiator longer, thus cooling it more...so the switch sees low coolant temps and turns the fan off.  Even though the coolant exiting the engine is hotter than normal. So maybe the radiator flow should be checked.

 

Almost all the kits I have seen monitor the coolant at the switch or near it....so you can turn the fan on or off based on the engine temps, not the temp of the coolant BEFORE it goes into the engine.  

[jrhone]

Oh and Ray's advice on a manual toggle switch is spot on...good to be able to override the temp switch and just turn it on for more cooling if desired.  I have almost never used mine, but its nice peace of mind knowing I can.  Or...you can put your regular fan back on.

[enoklite]

Thanks jrhone!

I have an e21 radiator installed so I don't know if the stock fan fits. Also, those are some very good points that you've made. Everything is getting its temp reading from someplace else so its hard to say where I'm at until I look into those items. I still have yet to take an actual reading/go through the gauge cluster grounds. I will report back ASAP!

Again, thanks to everyone for the massive help!

[MatthewCervi]

My car has an E21 radiator with an electric fan triggered by a thermoswitch off the bottom side of the radiator and it works perfectly (starts up around midway on the temperature gauge and never lets it rise much above that).  The switch is part # 61 31 1 364 272 - 91deg from an E21 or E30.

 

Like others have said...don't trust the gauge to be accurate without verifying.  I spent several years throwing parts at my car trying to figure out why it ran hot until I finally replaced the gauge with a NOS unit.  So if you have a spare gauge/instrument cluster or can borrow one from somebody, try that out before going too deep into this.

[jimk]

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