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Discussion Starter #1
My AC (manual) has stopped working. I have checked the following: 1. Relay (K19) - checks out fine. 2. All related fuses (cabin & engine compartment) - all good. 3. Clutch and refrigerant fine. Fan relay good. So - my AC button sometimes flashes, sometimes is solid, but compressor not engaging. I jumped the K19 relay (ground wire) and AC engages and blows cold and rad fan comes on fine. I could leave the jumper in place, but really don't want the air conditioning on all the time. Not sure what to check next. Any suggestions?
 

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is the condenser looking like its falling apart,, ie the radiator looking thing in front of the radiator this cools the gas and turns it back to a liquid for re-pump around the system as such if this fails to cool the system aircon wont work very common for them to get old and not do their job,,
 

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Discussion Starter #3
New condensor a few months ago. Charged properly. I have to think it is a sensor of some form that has failed......
 

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air temp sensor in below for idea
not sure of there is another temp sensor for heater in car fascia somewhere, i know gen 2 cars do as part of heater controls, looking a small grill normally around heater controls plastics if it does, might not have as not climate
 

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Discussion Starter #5
I appreciate the suggestions you are making. I had thought about the air temp sensor, but it seems to be working fine - the outside temperature readout I get on my dash accurately shows the correct air temp. The more research I am doing, I am wondering if another possibility might be the refrigerant pressure transducer. Not eager to check that out as it seems I will need to get under the battery tray and (as is always the case it seems) the bolts spin in the plastic base. But don't know of any other way of knowing if the switch is faulty.
 

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Check the aircon pressure switch in the pipe work, sounds like the system is not triggering because it thinks it has no pressure, but of course it does.

It’s part 5 in the pic I posted below, I think it’s under the battery in a R50 (I have a Cooper S so the air box is there).
 

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Discussion Starter #8
Thanks for the direction and schematic. Helps in understanding the system. Next step will be to pull out the battery and tray and see if I can get at the pressure switch to see if it's the issue. I can't see it anywhere, so figure that's where it must be located. arghhh....
 

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Discussion Starter #9
OK. Everything checks out OK. Compressor, clutch, relay, line pressure, pressure switch, fuses, evaporator switch. Relay is not getting signal from the computer to close the circuit. No other fault codes for the computer. Surely it's not the computer. A break/short in the wire from the computer to the relay perhaps? Any ideas on how to determine if it's the computer or the wire?
 

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Probe the connector at the ECU. Do you have a sequence for what the ECU is looking at/sequence of what is supposed to happen when you press the a/c button?
 

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Discussion Starter #11
Probe the connector at the ECU. Do you have a sequence for what the ECU is looking at/sequence of what is supposed to happen when you press the a/c button?
Thanks for steering this issue towards the determination.....

Wording getting a bit technical for me... But it sounds like you are closer than any other possibilities of what is going wrong. I had the car in for an oil change a couple of days ago and the mechanic put things on the screen showing 6 activities (I think) that occurred when the a/c button was switched. Things like pressure in line, pressure switch, relay (active), etc. Everything checked out good except for the relay - there were 2 measurements for the relay, one that it was functioning and the other that it was activated (not sure of wording, but the mechanic suggested it wasn't been given the "go-ahead" by the ECU. That's about the best I can describe it as a lay person!

Perhaps unrelated, I grounded the circuit (30 and 87) and the a/c functioned well and cold.

Does this make sense?
 

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Makes sense entirely. I'd love to know the operating sequence of what happened when the button is pressed. With that information it'd be easy to diagnose.

My suggestion was to 'back probe' the pin at the ECU to see if it was sending the signal to the relay. That way you would know if your issue was that the ECU wasn't sending the signal or if you had a broken wire between the ECU and the relay. Is that clearer?
 

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Discussion Starter #13
I will plan to take the car back to my mechanic and have him do another diagnostic. I will see if I can take a screen shot of the readout of the sequence and get back to you.

Meanwhile, now I need to locate the correct pin at the ECU (sure is a quite a bundle of wires!) - once that is figured, I understand what you are saying as determining if the ECU is failing to send a signal or whether the wire to the relay is at fault. Hopefully the latter??
 

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That's exactly right. Hang on a bit and I should be able to find the right wiring diagram for your car. I would very much appreciate the screenshot if you could manage that. I also have a mini sat on the drive with a flashing air con light. It's some way down the priority list at the mo as I have a lot on but with that info it would be a much quicker fix.
 

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Discussion Starter #15
Thank - I have been searching for the right wiring diagram but always seems to be a catch to getting at it when I find something. So certainly appreciate receiving it from you when you have time. No rush. Weather cool enough these days for fresh air and open roof.

I will definitely send you the screen shot. Should be able to get the mini into the shop early next week. (BTW - my AC light is flashing)
 

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Discussion Starter #17
Many thanks! I definitely owe you the display of the diagnostic when I see my mechanic. High priority now!

Will be interesting to see if we end up solving the same problem..... Best!
 

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No problem, just as an additional the wiring colour abbreviations for BMWs are a bit odd. BR/SW/GE means you're looking for a brown, black and yellow wire (bit odd to have three colours) and as you've probably already figured out it's on pin 13 of the ECU. The ECU controls it by switching the earth to the relay and the car should have a constant live to the control side of the relay fed by fuse F3 in the under bonnet fuse box.

Interested to hear how you get on. I may have a play with mine tomorrow too.
 

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Discussion Starter #19
No problem, just as an additional the wiring colour abbreviations for BMWs are a bit odd. BR/SW/GE means you're looking for a brown, black and yellow wire (bit odd to have three colours) and as you've probably already figured out it's on pin 13 of the ECU. The ECU controls it by switching the earth to the relay and the car should have a constant live to the control side of the relay fed by fuse F3 in the under bonnet fuse box.

Interested to hear how you get on. I may have a play with mine tomorrow too.
Thanks for clarifying the color codes. I may not have got that one figured easily. And hadn't identified pin 13 of the ECU. I'm just tripping along after you! So now, shouldn't it be as easy as jumping a wire from pin 13 to the relay slot (87), turning on the AC and see if the fan and compressor clutch engage? Wouldn't that tell me if the ECU is at fault or the wire routing from the ECU to the relay?
 

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My method would be:-

1) short the control side of the relay to ground (with the engine running) and confirm that the compressor clutch engages.
2) Test at the relay to see if the ECU is grounding the relay when you push the a/c button.

3) if (2) isn't working, test the wire at pin 13 of the ECU to see if it's being grounded when you push the a/c button.

4) if (3) isn't working, you're now into confirming the inputs to the ECU (pressure and temp sensors, believe you may have already done this?).

Garages have a habit of blaming the ECU when they run out of diagnostic ability. I'm always extremely skeptical when someone tells me that a garage has diagnosed there issue as a failed ECU.
 
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