My 2004 Cooper S got a brand new backup cooling fan and new drive belt in December, along with new idler pulley and drive pulley.

The AC hasn't been consistently cool lately, but I blamed Florida heat.

Then yesterday, in the heat, the engine temperature gauge spiked all the way up to hot and the red light went on. I was running the AC at the time. I let the car cool down for a few hours and was able to get it home after dark (headlights did not drain the battery) without getting hotter than mid-range on the dial... But it occurred to me that I hadn't heard the fan run in a good long while.

My Mini repair shop is shut down for vacation. An independent AC shop I trust took a look at the car today. They say the fan works fine if they bypass some sort of controller that was not yet visible to them. They believe this is an electrical problem relating to the controller device. (Sorry, I don't know the name.)

Does this scenario sound familiar to anyone? Is this likely to be expensive to fix?

Patty

 

The controller they are referring to sounds like the temperature sensor. The fan should kick in based on the temperature of the antifreeze. Usually, it's 210 degrees Fahrenheit for low speed and 225 degrees for high speed. Remember, combining a 50/50 water/antifreeze with a 15 or 16 lb. pressurized system, the boiling point is much higher, somewhere above 250 degrees.

If the sensor is bypassed, the fan would stay on all the time, whether it be low or high. Even with the AC on, so long as you are moving and not sitting still, the engine temperature should not shoot up too high (though the fan is designed to be on all the time with the AC on). The spike sounds more like an air pocket. If memory serves, I read another post that mentions a spike in temperature as a result of it. Check your reserve tank and make sure the antifreeze level covers the veins at the bottom of it.

 

The reserve tank was low when I checked earlier today but not completely empty. I could see the sides of upright plastic pieces inside the tank -- are those veins? I added about 3 cups of fluid before taking it to the shop, where I've now left it for the weekend... Would an air pocket keep the fan from kicking on? I'm not sure I understand how that works. Is it this: The entrapped air is too cool? So the fan doesn't do its job and the engine gets temporarily overheated? And the AC can't keep up with the extreme heat? (Because my AC was definitely blowing warm air during this spike.)...

If that's the trouble, would simple addition of antifreeze solve the problem, or is it necessary to do something akin to bleeding brakes?

(And thanks so much for taking time to answer.)
Patty

 

I refer to them as veins. Not sure what exactly you call them. But they seem to be the guide to go by when topping off the reserve tank.

No, an air pocket won't keep the fan from coming on. It can cause the temperature gauge to read a spike because the air will heat up quicker than antifreeze. I overlooked your comment about the fan not coming on. If that's the case, it could be the relay. Perhaps that's what the shop was referring to as bypassing. I would not do that, however.

Open up your bonnet (hood). Open the large fuse cover. It's the rectangular cover next to the driver's side strut tower and has a fuse emblem on it. First, verify the 50A fuse for the AC blower is good. Look inside the cover; it will show a four-bladed fan symbol to indicate which one it is (it is FL11 for my '06 MCS).

You will also notice four large relays. With mine, two of them are the different fan speeds. Each is indicated by a fan symbol followed by "I" and "II" respectively. Two of the relays are green in color, and two are a slight lavender color.

Being yours is an '04 S model, the wiring may be different. Your relays may be white in color. If that is the case, they will most likely be (from back to front): heating and AC blower relay, AC compressor relay, engine cooling fan low speed relay, and DME main relay. See if either of the two AC relays have a matching part number with the fan speed relay. If they do, swap them, then run your MINI until it gets hot enough the fan should come on. Sit in your driver's seat and keep an eye on the temperature gauge. If it spikes, immediately shut it off and put the relays back the way they were.

 

Thanks.
For clarity, the bypass was just to test the fan, not an attempted solution.
I'm wishing I'd kept my car at home this weekend instead of leaving it at the shop, but I was afraid I'd do harm by driving it further without a good understanding of the problem.

 

Oh, that's understood. I know what it's like not to have your MINI. Mine spent a week in the shop back in April. Boy did it go by slow.