Have a 2003 MCS with 65k miles. Put a new AC compressor in last year. This summer the only way to get the AC to kick on was to rev the engine up to around 5k rpm. Now the compressor won't ever engage. Checked fuse (F5), don't know how to check the relay. When the AC was on it seemed to draw a lot of power from the engine and would cut down the power.

Any one ever had the problem with having to rev up the engine for it to kick on? What is the problem?

 

Check your serpentine belt, as a potential first move..if its slipping it wont spin the accessories as well as it should.

The 5000 rpm thing is weird..like the clutch on the AC is not engaging.. Unfortunately I don't think switching the clutch on the AC is a easy replacement as it isn't sold alone.

Start with simple stuff..at 65k miles if you didn't change it..it's time.

Also if you have a smaller pulley and didn't go with a shorter belt... You need it.

 

Last summer when the new compressor was put in I put in a 15% pulley and a new smaller belt too. I might take it somewhere and see if they can check the pressure valve (I've read some people saying it might be bad). Though I don't know if a shop can test if the system is low without the compressor running or not. If I could just get that compressor to run I can hook up a refrigerant gauge that I have. Ughh

 

The AC clutch is available separately these days - there are several threads on it.
Definitely sounds weird that it wouldn't engage until 5k RPM, that doesn't really make sense in that the clutch is binary and not speed dependent.

 

How are you checking if the clutch is engaging or not?

Have you checked the pressures with the manifolds?

Usually, if the pressure switch is faulty, it won't engage at all at any circumstances.

 

I will turn on the AC and go look under the hood to see if the AC compressor is turning (and not just the part that the belt is hooked up to).

I'm not sure how to check the pressur switch. I can't even find the darn thing. I have hooked up an AC gauge but it won't read correctly since the compressor does not turn on.

Maybe I should take it into a shop and have them test the pressure switch (wherever it is located). Along with testing to see if I am low on refrigerant. Are shops able to fill the lines without the compressor working?

Luckily it is beginning of fall and I will have cold temperatures and 12 inches of snow to worry about for several months during winter.

 

You can check the pressure on the low pressure side to see if there is any pressure to check for presence of refrigerant.

Also just by hooking the manifold on the high side you can see if the clutch is engaging or not by watching the fluctuation on the needle. Fluctuation = clutch is engaging/disengaging. This will be extremely helpful for you since you can't see the clutch directly. No need for actual reading.

If there is some pressure and fluctuation is present that means you are short on refrigerant judging from lack of cooling.

Just remember this, you don't add to the high pressure port no matter what. It may blow up on you taking out your hand if you are holding the can.

BTW who did the AC work last time? Did it work fine when it was repaired?

 

To the op....
Did you swap out the dryer and pull a vacume BEFORE refilling the system?
I ask because some of the symptoms you describe would match this having been done, or perhaps a clogged/failed expansion valve....the drier is swapped out cause it filters out chunks of faile compressor out, and removes moisture..which can destroy the compressor, turning the oil into a black sludge, and the air when refilling a system will reduce/prevent the system from working....
While ac work can be diy'd to save a few $$, it does usually reqire a trip to the shop to get a vacume pulled on the system to dry it out, and check for leaks before refilling...

 

DailyDriven & Zippy,

Thanks for the info. The gauge i have only hooks to the low side. What you said makes sense. I did the work last summer. I had it tested for leaks and vacuumed out before i changed everything. I replaced the dryer too. Didn't replace the expansion valve. Where is it? Do i have to go thru the dash to get to it?

I'm sort of a noob when it comes to AC but not afraid to learn how to do something. Just hate paying the high price of maintenance on minis. But there are only so many things i can do until i have to have a pro get involved.

 

Now after you did all the work, did the AC work as it did before. Let me roll back, did they draw vacuum for 30 min let it stand for 15 min or so then checked for leak and charged the system under vacuum? Did they put in about a pound of r134a? Also u need substantial compressor oil in the system since You replaced the drier and compressor. Did they put enough back in?

Sorry to say, I have yet to meet an honest mechanic, I don't trust any mechanics out there. I watch them do work when I let them touch my cars. Like changing tires.

ABSOLUTELY Nothing wrong with DIY, we all learned some where, some how, and some time ago.

Just gotta do things right the first time to be cost effective at least from my experience. I personally tackle DIYs projects to learn for the most part, and I usually don't end up saving money for the initial job because all the tools purchased; More like paying up first for repairing other family vehicles and that saves money.

Anyways let us know how things go.

 

Thanks for the encouragement! It did work properly after I did the job last summer. A shop vacuumed and tested the system for leaks. They didn't recharge the system since I was going to redo the compressor. When I opened the lines I closed the ends since I read to not leave them open. I added the r134a when I completed the job (yes about a 1lb). I added the correct amount of pag oil to the compressor before the install. Maybe I should have added more.?

The pressure from the low side reads very high, but because the compressor is not running.

Maybe I'll have a shop test the pressure switch as a start. Not sure when i will get to this. I might just wait until winter is over and then tackle this in the spring once temperatures start rising.

 

UPDATE! I'm finally getting back to my AC problem. So after reading around for awhile I realized my DIY skills aren't that good for my first time working on an AC system. When I initially replaced the compressor I had a shop evacuate the refrigerant and then I took out the compressor. Replaced the compressor and drier. Once everything was sealed up I failed to have a shop pull a vacuum on the system and charge it. I just filled it with a can of r134a. I think ZippyNH nailed the problem by suggesting that I needed to pull a vacuum prior to charging with r134a. This is probably why it failed again.

So, now that it doesn't work, will I have to replace the compressor OR do you think I just need to have the system evacuated, vacuum pulled and recharged?

Your help is much appreciated. Thanks!

 

Hmm, not sure. I can't think of a technical reason that air in the system would kill the compressor, but maybe someone else can. Hopefully you can just pull a vacuum, add R134a and get back to normal. AFIAK, no vacuum just means water/air = lack of efficient cooling.
I've done the dead compressor swap, and hope I don't have to do it again (for both $$ and time.)

 

Hoping someone who know can confirm or deny if the following is possible in a MINI.

In my Honda, I know that the compressor will not kick on when the pressure is low. It's a safety feature to make sure the clutch on the A/C pulley will not engage if it's possible that the oil in the system is low. The shop that vacuumed and refilled it jumped the terminals on the compressor with a paper clip just for a few seconds. We wanted to prove that the compressor worked before wasting time and money to refill it.

Hope that helpful.

Alex

 

AlexQS, did they jump with the paper clip with the 30 and 87 pole on a relay? I saw a video this morning showing how to do this, but just don't know which 87 to jump to. Thanks. Video is below.

 

Sorry, I don't know exactly where on a MINI, and don't yet have a book.

On the Accord, the kid at Oil Can Henry's did it, jumping terminals right on the compressor itself.

 

Tried this jump last night. Only one of the 87s is used. Jumped the 30 to the 87 and nothing happened. The A/C compressor didn't come on nor did the power steering fan (since I've read that they use the same relay). Going to get under the car later tonight to see if power is getting to the compressor by testing for 12v. This should tell me if power is even getting to the compressor. If it isn't then there is something else wrong. Pressure switch that is bad, fuse, relay, etc.

Can I directly jump the AC compressor to the battery to see if it works?? Kind of like how you can do it with the cooling fan. Anyone ever do this?

 

Hi guy,.. So sorry, I maybe should not have said anything in the first place, since I am so new to MINI, and can not guide you specifically.

I would NOT jump from the battery to the compressor. The compressor after all is not an electric motor that runs on power, we're only talking about a switch to engage the clutch that is likely stepped down a lot in voltage and amperage. I wouldn't want you to fry it by giving it approximately 60 or more amps of around 12 volts. That's way too much!

Don't the people that vacuume and fill the system check it for free -before they fill it for $charge ???

Alex

 

They probably do. I just don't have much time to get it in and wanted to try and diagnosis the problem before they spend hours trying to figure out what the problem is. My best bet is to take it in, tell them my compressor won't kick on, and if they can test it and also see if the pressure is too low. Thanks for the word of warning!

Andy

 

MY AC IS WORKING!!! The electrical connection to the compressor was not making a good connection. I don't know why I didn't think about this before, but this is probably why I would have to rev up the engine to around 5k rpm last summer to get it to kick on. It was low on refrigerant too. I had it filled today. Thanks for all of your suggestions.