Hello All,
This is my first post on North American Motoring, but have been lurking for quite a few years now. Unfortunately the guys over at MiniMania tell me I don't have a 'Real Mini' because it's not the old style and don't want to help me.

Either way, here is a little backdrop on my current issue and what I've done to try and debug. For what it's worth, I have done extensive searches on this site, on Mini Mania, and over the web to try and find more solutions.


Tis the season for Mini maintenance, and I've been trying to solve this issue for a little while. My mini is a 2002 Mini Cooper S hatch with less than 50k miles on it. I purchased it almost 8 years ago used from a collector who had been keeping up on routine maintenance but still needed a battery and air filter replacement.

A week or so ago the A/C in my car stopped working somewhat suddenly, at the time I was bothered, but knew that there could be a variety of reasons for this to happen. The first thing I checked was to see if the compressor is actually turning on. Without taking the car apart I am able to see that the compressor clutch isn't turning. I'm hesitant given the mileage on the car to assume that the compressor or compressor coil is shot. To ensure what the cause of this is, I have gone ahead and checked the following:

1) AC Fuse (Engine Compartment) 30A, looks and is not blown.
2) AC Fuse (Cabin Compartment) 5A, looks and is not blown.
3) AC Relay (Engine Compartment). When the AC is turned on in the car when idling, the click from the relay is clear and crisp, although it sound sound worn down. I bought a new relay for this and put it in. Much louder click, so I give this a passing grade.
4) r134a level. I took the low pressure cap off the AC system and connected my gauge. The pressure reading immediately went up into the red. I turned on the car and the pressure stayed the same in the system.
5) r134a test, to ensure the system wasn't staying off due to over-pressurization, I had a mechanic legally remove some of the r134a from the system. (EPA etc). This brought it down to the correct 'operating' pressure, but still the compressor clutch would not turn on.

I know steps 4 and 5 both rely on the compressor actually being on, because without the compressor turning on the pressure reading is not accurate or even correct. However this was the best I could try without the compressor turning on.

From here, if my lurking has served me well, I know that the possibilities are as follows:

1) Compressor itself is shot, $600 replacement + my time and effort to replace and a recharge.
2) Compressor clutch is shot. Can't buy this on it's own, and would need to replace the whole compressor.
3) Compressor coil is shot. $95(?). This is (apparently) a common problem on early new Minis. Would still require me to get the system drained, replace the coil, test it, and recharge.
4) One of the multiple sensors are telling the compressor that a different external situation is happening, and thus telling the compressor not to turn on. I don't know exactly how these sensors are wired to know if the relay would even activate if any of the sensors are tripped or not. Speaking of which, could someone knowledgeable on the subject tell me all the possible sensors that would be preventing the AC Compressor from turning on? I only know of the refrigerant sensor and the pressure in the system sensor.
5) If there are other things I haven't tested but should please let me know! I'd like to take every opportunity I can to learn more about my car.

From what I've said, where do you guys recommend I go next? I work daily and need the car to get to and from work, so leaving the car in pieces for more than a weekend isn't an option I'm excited to consider. If I need to replace the compressor I would be able to finish it over a weekend once the parts arrive.

The only somewhat straightforward test to do is check the OBD2 readings and error codes and try to deduce something from those. However with the Mini most standard OBD2 devices can't read the codes. I have one that for sure can at another property, but cannot access it until this weekend.

I have the time, ability, and money to replace the entire compressor, but I would really rather not.

Thanks in advance for all your help, and I will be happy to provide more information, answer questions, and take pictures if needed.

Regards,
Chris

 

I speed read thru your post and didn't see if you have auto or manual AC. In either case, I would recommend you verify if the compressor clutch has fail. If you can check the resistance of the coil, which if good should read almost like a dead short with a DMM. If it read good the next step is to see when you switch on AC the clutch solenoid is getting power. To do this you have to figure out if the AC control switch one side of the coil to ground to energize, or switch it to +12V to energize it. I think the latter is more likely as there is a relay. I think there is a single conductor connector by the radiator that is the compressor clutch on/off.

As you have observed the clutch does not engage I would not condemn the compressor until this is verify.

 

I'm curious about the outcome, and how you get to it, because my AC failed shortly after I bought my car, and my diagnostics were the same for Chris's first four tests. However, since I ride my motorcycle most of the summer, and have the family wagon on the hottest days when I really need AC, fixing this problem just hasn't bubbled up high enough on my priority list yet.

Scott

2004 R50 5-speed with auto climate control

 

Have you guys checked the Sticky at the top of the Stock Problems/Issues section where I am moving this to? If the low speed fan does not come on the AC is not going to work. Also check out the video below on how the ac works.

https://www.northamericanmotoring.co...c-problem.html

 

The AC in my '03 S worked fine even when the low speed fan was inoperable. Perhaps R53Coop was referring to the power steering fan- I think the AC will not work if it doesn't.

 

Both fans work in conjunction with relays. As far everything I have read and with my own personal experience without a low speed fan the AC head pressure goes bonkers. The thread I referenced has 1407 postings on the matter of the low speed fan and there are numerous on how the AC is impacted.

If the low side pressure is high than either the compressor is shot or the expansion valve is stuck open. Need to know what high side pressure is.

 

I know where you are coming from, with so many newbies don't bother to do some leg work with their problems. Many can't be bother to invest the time to make a intelligible post with the most basic background. Not so with this OP. He has detailed what he know, not know, and gone thru very reasonable fault isolation steps. The sticky post you point to is not all that useful as I myself have read just about the entire thread trying to ascertain if my low speed fan is kaputt. I ended up devised my own test to confirm mine is just fine. The low speed fan is very loud and unless you have prior experience the loudness difference it is very hard to tell.

Your assertion that if the low speed fan (better put - fan low speed) does not run the AC will not engage invites some scrutiny. I don't know the answer for sure but I reason it not the case. The computer do not have direct means to know when low speed does not run. For both speed, all it controls the hi and lo speed relays but has no mean of knowing if current is being drawn by the fan. It has two or three things it relies on for AC function:

1. Engine coolant temperature
2. Refrigerant excessive pressure
3. Power steering cooling fan kaputt - per other poster
4. Depends on if it is auto or manual AC the call for cold functions a bit differently

So assuming the OP's fan low speed does not run, the compressor clutch should engage (when call for cold) at least until the coolant temperature reach the panic point. Per the other poster that the AC will not run if the power steering fan failed make sense to me, as it is a elevated safety problem.

 

To OP. It makes a big difference if you have auto or manual AC as to what can cause the compressor clutch not to engage. Manual AC is much simpler. I want to point out there is an evaporator temp sensor in the center console that the BCM uses to determine call for cold.

The compressor clutch is control by the AC compressor relay which switches on/off +12V to the solenoid. The other terminal of the solenoid is wired to ground.

If it were me I will first verify if +12V is being supplied to the clutch solenoid when you know the AC should be switched on for call-for-cold.

If you have auto AC things get very complicated as there is another CPU involved.

 

The highlighted section above is how a lack of slow speed fan cooling the condenser will impact the AC. I know that the high speed fan set point relative to the AC is 261 PIS. At 116 PSI the low speed fan should come on, so with no air flow across the condenser the system spikes.

IMO need to have a set of AC gauges so both the low and high pressure can be tested. Until then, just throwing darts at the board.

And last, to UCDNebulous, rather have you ask the question than ask no question at all.

 

R53coop, thanks for the pointer. I hadn't looked into that sticky because it didn't look related to my problem. None of the other AC troubleshooting steps mentioned looking at resisters hard-wired into the radiator cooling fan, so this was a great hint.

Scott

 

Hi All,
Just an update on my AC issue. I went ahead and checked the OBD-II codes and got no codes of interest. I also used high/low pressure gauges to check the high and low pressures, both of them seemed relatively normal (if anything high because the compressor isn't coming on). Also all fans seem to be coming on as needed.

To update some users, my car is a Cooper S, 2002 which I believe only came with manual transmission. I also believe the AC is manual, but I do not know for sure.

Finally I used a multi-meter in the socket for the AC relay and found that there was no continuity, which means the coil is shot. I have gone ahead and placed an order for a new coil which cost me around $80 on Amazon. I will install when I next have a chance to (should be the weekend of the 2nd) and let you guys know the results.

Cheers,
Chris