Firstfives.org

My last question was aimed at the four prong lower radiator sensor on my 635. As both my 528i's have ( non working ) a/c, aux fans, how do I know if they work?

Best of my knowledge both cooling systems are tip top, never had any problems. I can tell when it's 95 degrees, humid, but so far no needles sneaking over the line.

Very good question. The switches rarely fail, but nothing lasts forever. I have seen partly plugged radiators which flowed poorly, slow enough that what water did pass thru would cool down so the fan wouldn't turn on. Anyway, how to test is to put a piece of cardboard in front of the radiator and watch the gauge so you don't over do it, but see if and when the aux fan comes on. Low speed should come on just past half way, high speed somewhere around 3/4 on the gauge.

Since I am not sure my aux. fan works either, I am going to do the cardboard check.

But, was also wondering, where everyone's temp gauge sits at under normal conditions.

Mine sits about and 1/8 below the midway mark.

Is that pretty normal for stock radiator? Seems like I remember my prior 5's running around the first quarter mark.

Not looking at it but I believe there are four white lines. First, left has a blue area, for recommended warm up in neutral, very cold outside air temps.

Depending upon the temp of your thermostat, the needle will sit close to one or the other of the next two at normal operating temps. Much above the second one, especially climbing, is cause for a flush and fill.

Besides the splashing mess ( and clean up to save pets ), pulling the three hoses, right side bracket, two screws on the fan shroud, the radiator comes right out. Do use a piece of cardboard between the fan blades and radiator to avoid creasing the radiator fins.

Once out, a hose in the top and bottom pipes usually cleans out the crud pretty well. You can just pull the hoses and squirt in the top pipe in the car, but out, you can clean the a/c radiator fins too.

Easiest to put the fan shroud in first, or be prepared for a certain amount of brain teaser turning and pushing. The radiator sits in two rubber mounts
that sometimes need a dab of water, soapy water to slide into. Two tabs need to fit into slots in the frame for the fan shroud to fit perfectly.

Yes there's a block drain, and flush sauces for super chunks, but if your car hasn't been sitting for ten years chances are all you need is a drain and replace what drained out.

Write again if you do it, we'll tell you how to get the air out of the system.

And then the obvious test for just the aux fan itself-with air cond car
Put air settings on cold, turn the fan dial.... aux fan should spin

cpalmer wrote:Since I am not sure my aux. fan works either, I am going to do the cardboard check.

But, was also wondering, where everyone's temp gauge sits at under normal conditions.

Mine sits about and 1/8 below the midway mark.

Is that pretty normal for stock radiator? Seems like I remember my prior 5's running around the first quarter mark.

I'd say anywhere from the 1/4 to the 1/2 mark. It depends of course on both the thermostat you are using and the calibration of the gauge itself. I had an E24 one time that always ran hot, until I figured out maybe the fact that it started out past the blue might have something to do with it. Repositioned the needle so it went from blue to red instead of just this side of blue to past red and it was much better.

You could check just the fan by unplugging it and applying 12v to the high and low speed connection. There was a thread a few years back about the resistor in the low speed circuit getting fried and failing, but we haven't heard about that for a while.... If that has recurred in your car the low speed circuit would be out -- no fan with A/C or the lower temp switch in the radiator. Good news is the resistor is cheap to replace from Radio Shack.

If we think it's worth your bother for the thick among us, like me, I would take photos, edit a FAQ to submit.

Without going out there and sorting backwards from any wires that may lead to the aux fan, (under, around radiator, charcoal canister, etc.) I would have no idea what plug, connector to put a 12v what, battery with wires off it ? or what the resistors are, look like, where, to test (?), to go, or not to Radio Shack.

Unfortunately you have the curse of not knowing how stupid other people can be, about things you learned as a kid.

Karl in KS wrote:You could check just the fan by unplugging it and applying 12v to the high and low speed connection. There was a thread a few years back about the resistor in the low speed circuit getting fried and failing, but we haven't heard about that for a while.... If that has recurred in your car the low speed circuit would be out -- no fan with A/C or the lower temp switch in the radiator. Good news is the resistor is cheap to replace from Radio Shack.

That tests the fan, but not the system. It doesn't matter if the fan works if it doesn't come on when the car gets hot. It's a good troubleshooting tip if you do the cardboard test and the fan doesn't come on, but only then, IMO.

As far as which wires, I don't remember what the 6 series used, but on E12's at least (and 23s and 28s) there are a pair of each small connector and larger connector terminals. Short both of the smalls together to test one speed (I think high, but don't quote me) then short the other two together to test the other speed. All with the ignition on of course, but the car doesn't have to be running. But start with the cardboard test, it tests the whole system.

So, my aux. fan works after doing the cardboard test, (thanks W.). I flushed the cooling system last summer when I got the car and drove it down to Ca. through 100 weather, with the temp gauge pegging and STRESSING out. I did it again when I replaced the started a month ago.

Think I mentioned it. Nothing like driving through 100 degrees with windows down, heater on full blast, no sun-roof. Was thinking about the German engineers in that urban myth driving through Texas.

Since then, I figured out how to let all the air out if the system, set the timing, dropped in a pertronix and the car now sits between the 1/4 and the 1/2 mark, so I am all good there. If I am going down hill in chilly Oregon weather, it drops to the 1/4 mark.

The big bonus was my last trip down to California a couple months ago, I was driving from San Francisco to San Jose and was like "why is it so freakin' cold???".

I'd turned on the A/C by mistake, ( I didn't think it worked), and it took 5 minutes, but I realized my A/C was blowing cold!!! Sweet!!!!

Now, I am off to change my manual trans. oil as I know my car sat for years somewhere and it must e pretty old.

This sites rocks.

I can't wait to drive through summer heat this year!

Thanks T. hans and Mike W.....once again.