Air con - compressor clutch not engaging, maybe?

[r00x]

Christ, I'm having so many problems with this car anyway yeah, my air con was dead today and I was dying myself, driving around without it. Need help!

Symptoms: heater set to cold, fan on, press air con, button lights up, engine RPM increases slightly (!!) but compressor doesn't appear to kick in. Compressor clutch does not appear to be spinning at any time. Engine will idle at or just under ~1100RPM with air con turned on but compressor not running.

It worked fine yesterday. A couple of days ago it didn't kick in on the motorway. I assumed going from dead stop to matching the engine at ~3-4000RPM was unappealing and it was waiting for the revs to drop. I don't know if it DOES work that way, but when I dipped the clutch and let the engine reach idling speed, it kicked in and worked fine.

But today, nothing. The engine does seem to increase RPM as if anticipating the compressor will kick in, but the compressor never does.

Other notes:

• The pressure sensor and clutch connectors seem to be plugged in. Gave them a wiggle, no difference. Can these be tested with a multimeter? If so, how?? What readings to expect?
  
  Air is cold when set to cold, HCV and HCP seem to be working. Just no flippin' air con!
  
  The air con, when it did work, put significant drag on the engine. Surprised me actually, it's like someone toggling the handbrake, especially if you're in low gears and low speeds, but you can even feel it a bit on the motorway. Made the car a bit hard to drive sometimes.
  
  But air was lovely and cold, seemed to work really well (handbrake-effect aside).
  
  Did dribble some water into the passenger footwell on one or two occasions.

 

[martinthrapston]

Won't engage if air con gas is below a certain pressure,also check fuse in engine bay,iirc it's a 20a fuse,also you may have a leak,need to get it leak tested

 

[r00x]

Thanks for the suggestions. Crap, a lot to do then. I thought if the pressure was low it would engage the compressor, run for approx a few seconds, then switch off? Is that not the case? I base this assumption on what it did with the heater control valve (I had an HCV stuck to hot once - and when that happened the air con would run for a few seconds then turn off, presumably detecting the heat or something).

Can I check the output for the pressure sensor somehow? Is there a voltage across the pins I should be expecting, maybe a range which is "good" pressure? Or am I better off blagging one of those £30-40 refill kits and having a go at refilling? I've used those before, they include lubricants and sealant for leaks and things and generally seem to work great...

Can I verify if the clutch is working by manually activating it? The clutch wire is just 12V, right? If I removed the wire, then pulled the electrical pin on the compressor to 12V across a fuse, I'd immediately see if the compressor clutch was at fault as if it wasn't broken it would spin, right?

 

[cletus100]

Don't bother with a refill kit, £40 plug it in and refill to find you've got a leak, try an AC service place that checks the system and only charges you if the system is OK and needs refilling, if you use a refill kit be careful of frostbite if there's a leak and your fingers are next to it you can lose a finger (not joking). The AC clutch should have a 12 volt feed and an earth when AC is requested. AC will turn on regardless of needing hot or cold air into the car.

 

[r00x]

Cool, thanks for the advice! Maybe there is a bigger problem here then, I'm fairly sure my AC will not run if the heater isn't set to cold. The compressor will turn off after a few seconds if the air coming out the vents isn't set to cold (when it was working, anyway).

 

[lusid666]

AC should run fine with the hearer on hot, thats one of the best ways to demist the car when its cold outside.

 

[cletus100]

AC should run fine with the hearer on hot, thats one of the best ways to demist the car when its cold outside.

:clap: glad you agree.

 

[Anonymous]

Won't engage if air con gas is below a certain pressure,also check fuse in engine bay,iirc it's a 20a fuse,also you may have a leak,need to get it leak tested

+1

AC should run fine with the hearer on hot, thats one of the best ways to demist the car when its cold outside.

+1

There should be an oil/lubricant in the system which is almost luminous yellow/green (was that colour in mine). If you have a leak, you may be able to see if there is the oil/lubricant on any of the pipes. Well, the ones you can see anyway!

 

[jifflemon]

Kwik fit were running a no-charge if we can't get it 10degrees cooler campaign....

Now whilst I put kwik fit right up there with solicitors and MP's, if you've got a leak, they've just diagnosed it FOC (leaving you to replace whatever bit is dead)

However, as you'll still need a re-gas, if you've any decent air-con places nearby, they'd be my first first point of call.

 

[r00x]

It's working again! :thumbs: Which is just as well because I would've died trying to drive home in the heat today

I found the culprit when planning to test the compressor clutch. This would necessitate removing the clutch power cable, but when I went to do that (which required actually looking at it, unlike my earlier attempts to just wiggle the connector), I found one of the cables had sheared off:

Fancy that!! That might also explain why it felt like someone was playing with the brakes all the time when I drove with AC on, if the wire was going then the compressor must've been cutting in and out continuously. Fixed it and drove back home with it on tonight and it was way, way smoother to drive.

Happy ending!! Thanks for all the suggestions. It will be going into the garage soon, will get them to give it a check over as well, in case there are any other problems, like this not-running-on-hot thing.

 

[Anonymous]

Good news and glad it's sorted. Quick, cheap fixes are the best! :thumbs:

 

[Wild E. Coyote]

Just to join this thread. Mine a/c system is working ok, but is it normal to feel compressor kicking in and out? I mean, if I drive 90-100 kph, I feel jerk as it kicks in. When I had a focus 1.6 (Mk1) it didn't feel like that, I would assume being a bigger car that it had probably slightly bigger compressor and the engine was smaller. Yet, it was much smoother in operation.
The puma was porperly serviced at Ford dealership and the system needed top-up. It is cooling down nicely, it is just these jerks that I don't like....

 

[ewizzy]

Mine jerks when it cuts in and out. It's normal.

 

[ewizzy]

Mine jerks when it cuts in and out. It's normal.

 

[Wild E. Coyote]

Ok, thanks of claring that. As I said, focus was much smoother in operation....

 

[r00x]

Mine was jerking before... now, not so much, it's much smoother, but you can still feel a subtle change in the output power of the car when it's cycling. There's probably something else wrong on mine now though so don't take my word for it :lol: