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,,

 

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

 

air temp sensor in below for idea

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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

 

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.

 

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).

 

 

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....

 

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?

 

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?

 

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?

 

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??

 

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.

 

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)

 

Ha, funny how someone else struggling prompts you to getting round to something earlier...

Wiring diagram:-

newTIS

Required conditions:-

https://www.newtis.info/tisv2/a/en/r50-cooper-hat/wiring-functional-info/body/heating-air-conditioning-functions/evaporator-control/compressor-control/X04Cvq1

 

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!

 

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?

 

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.

 

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.

Hopefully in the home stretch for diagnosing. I will confess that electrical terminology is not my forte, so before doing anything too destructive to my ECU, I need a bit more help in clarifying my observations to date. Using my voltmeter and discovery to date.....

1. Shorting the control side of the relay (30/87) engages the AC clutch, compressor, fan = nice cold air.

2. All the inputs to the ECU confirmed functional

3. Constant 12v at connection 30 on the relay

4. Relay connections 85 and 86 become a closed circuit when engine running (14V approx.)

5. Circuit 85 and 86 remains closed when AC button pushed.

So - here’s my question. When I push the AC button, all things working as they should, my understanding is that the electromagnet (low current) is energized (+12V) and causes the AC clutch circuit to close. But the circuit is always closed with the car running. Or… Does the electromagnet switch instead activate when the low voltage circuit opens (85/86 becomes an open circuit).

Sorry if my electrical terms and descriptive are a bit lame - hope you understand my descriptive.

 

Thanks for the direction. I have done 1) and 4) and all good. So I have 2) and 3) to do before even beginning to suspect the ECU is faulty . Fingers crossed... Keep you posted.

 

I'm afraid I'm struggling with your description of what you're seeing. please don't apologise, it's a tricky thing to convey over text only.

In (1) you state shorting the control side of the relay but describe shorting the load side.

In (2) you say the inputs are functional. I presume that we know that the ECU is receiving signals but do we know whether or not the signal (for pressure) is in the range that the ECU requires it to be to activate the AC? Remember in the system description that I linked to it required the pressure sensor to be within a range. Did the garage's computer say it was within that range?

The other points I think we are going to need a picture of where you are taking voltage readings.

However, to answer your actual question...

The electromagnetic clutch is energised to engage it. When it is de-energised it freewheels and when energised it locks the mechanism to allow the belt to drive the AC pump.

From the way you asked the question however I believe that you may have misunderstood how a relay works and what is meant by a 'closed' circuit.

If you remove the relay and start the car, do you have battery voltage at 2 of the relay connectors? If so, which ones? A picture would be great if possible.

 

I'm afraid I'm struggling with your description of what you're seeing. please don't apologise, it's a tricky thing to convey over text only.

In (1) you state shorting the control side of the relay but describe shorting the load side.

In (2) you say the inputs are functional. I presume that we know that the ECU is receiving signals but do we know whether or not the signal (for pressure) is in the range that the ECU requires it to be to activate the AC? Remember in the system description that I linked to it required the pressure sensor to be within a range. Did the garage's computer say it was within that range?

The other points I think we are going to need a picture of where you are taking voltage readings.

However, to answer your actual question...

The electromagnetic clutch is energised to engage it. When it is de-energised it freewheels and when energised it locks the mechanism to allow the belt to drive the AC pump.

From the way you asked the question however I believe that you may have misunderstood how a relay works and what is meant by a 'closed' circuit.

If you remove the relay and start the car, do you have battery voltage at 2 of the relay connectors? If so, which ones? A picture would be great if possible.

I'm digesting your advice. I believe I understand the principles of the relay. I tested it this morning. Used small 12V battery charger. Clicks when +12V applied to terminal 85 and ground to 87.

To answer your questions, I have power at relay connectors 30 (always) and 85 (car started). 85 and 86 being primary (activates electromagnet); 30 and 87 being secondary (clutch). When car running and AC button depressed, relay electromagnet not closing (finger on relay, no click).

I agree I need to bite the bullet and take the car in to the garage and have them run another diagnostic. Make sure pressure is in range (I understand low pressure cut off is somewhere around 50 psi, but not sure).

I am at the point where it is unlikely I will sort this out to a fix without more sophisticated equipment and better understanding (I think that's becoming more obvious each day! Ha!!) . At best, I hope to be able to more intelligently converse with the mechanic and have sufficient evidence of the issue not being attributable to a faulty ECU as first course of remedy.

And, I do like to learn....

 

That's much clearer, thank you. Please don't take my comment as negative criticism, It sounds like you're giving it some real effort and conveying this kind of diagnostic route via writing alone is difficult. There are still easy tests you can do on the drive.

If you set your multimeter to continuity/resistance and check between pin 86 and battery negative (whilst turning AC on and off) what happens? This is the terminal that should be earthed by the ECU when the AC is selected on. If this is being earthed with the AC selected then you just have a faulty relay. Just because a relay clicks doesn't mean it is making a connection so people often go down the wrong diagnostic path when this happens.

If that doesn't work, leave one lead on the battery negative terminal and move the other lead to pin 13 of the ECU (the wire we previously talked about) You'll need to 'back probe' the connector or use a wire piercing test lead (costs about a fiver) so that you can connect to the wire with the ECU plugged in. You're looking for the same results as in the previous test. If there is continuity/low resistance when you switch the AC on this proves a broken wire between the relay and the ECU.

Before anyone moans about piercing wires...you also need to go back to where you used your piercing tool and fix the puncture in the insulation.

 

That's much clearer, thank you. Please don't take my comment as negative criticism, It sounds like you're giving it some real effort and conveying this kind of diagnostic route via writing alone is difficult. There are still easy tests you can do on the drive.

If you set your multimeter to continuity/resistance and check between pin 86 and battery negative (whilst turning AC on and off) what happens? This is the terminal that should be earthed by the ECU when the AC is selected on. If this is being earthed with the AC selected then you just have a faulty relay. Just because a relay clicks doesn't mean it is making a connection so people often go down the wrong diagnostic path when this happens.

If that doesn't work, leave one lead on the battery negative terminal and move the other lead to pin 13 of the ECU (the wire we previously talked about) You'll need to 'back probe' the connector or use a wire piercing test lead (costs about a fiver) so that you can connect to the wire with the ECU plugged in. You're looking for the same results as in the previous test. If there is continuity/low resistance when you switch the AC on this proves a broken wire between the relay and the ECU.

Before anyone moans about piercing wires...you also need to go back to where you used your piercing tool and fix the puncture in the insulation.

Not once taken your comments as criticism. Always supportive. I actually am amazed by the direction (and patience) you have offered. I will take these next steps and keep you updated... There will yet be a celebration when this is all resolved!! Many thanks again....

 

Update: My error - relay 86 is hot so connected pin 85 to battery negative as you directed. No continuity. So went to DME for next step in checking that continuity occurs when pin 13 connected to battery negative while AC switched on. But uncertain because wire at pin 13 (if I am reading wiring and location diagram correctly) is not BRN/BLK/YEL. Here's a photo of what I am looking at. Wire looks to be RED/VIO perhaps? Can you help clarify for me?

 

Apologies for the slow reply, been a bit busy. I was dubious of the wiring diagram when I saw that code, I've never seen a single core cable with 3 colours in a car. Are you able to check the colours on the wiring diagram by lifting the fuse box and seeing what goes to that position? It may not be possible to check this way because of the internal conductors in the fuse box but worth a quick check. I will check on mine too as it should be the same as yours.

Also I just wanted to check that you are testing the earth side of the control side of the relay is earthed with the AC selected? Your last post reads like you may be testing without selecting the AC on.

 

This is interesting. And yes... I did check with the AC selected. Took the car in to my mechanic today. He was also intrigued, as the different sources he had on computer for wiring diagrams showed the 3 colors and pin 13. He finally landed on a diagram that showed the brown/black/yellow wire from pin 93 on the short DME connector. He assured me that this was it, and that pin 13 was the throttle body power pin. Anyway - tested the wire (from pin 93 - it was black/brown/yellow) and no continuity. Which still leaves me wondering if that was the right wire - if not, one wouldn't expect there to be continuity. So - his diagnosis ended as a faulty DME. At this point, I may as well run a ground wire through a toggle switch from the relay (85) and, as I should need AC, just turn it on and off using that as a workaround. Sure do hate giving up!

 

Quick note. May explain my confusion around pin 13. I just found an old discussion that clarifies pins 82 to 121 are represented as "B" 1 to 40. Explains perhaps why I see the Brn/Blk/Yel wire at pin 93/13 and why pin 13 (red/vio) is the electronic throttle body power. Make sense?

 

The pin in your picture is definitely the wrong one. If you have another look at the wiring diagram I linked to it has a hyperlink next to the pin number. If you click on that it takes you to a picture of the connector. Pin 13 should be on the smaller (40 pin) connector.

Another poster on here posted the following in another thread:-

ECU pinout?

Hello, I've been lurking this forum for a little bit and feel ready to post... I will be collecting my 'new' 2003 MCS next week. One-ball exhaust mod will be done on the very same day and I've already ordered a 15% pulley+belt. I happen to have a spare SMT7 piggyback (about the same...

www.mini2.com

 

I missed on the hyperlink. Would have kept me on the right path had I not overlooked that earlier on . Sorry. Now I have my bearings. No continuity when probing that pin/wire. Going to get my mechanic to run through the sequence again to be certain all the conditions are being satisfied before attributing things to a faulty ECU. I'll let you know the outcome and hopefully still provide you with a screen shot of the diagnostics.