Now I need help!

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Chaser

Chaser

New Member
Posts
2,175
2004my TD4

AC has just stopped working without warning. It was working perfectly this afternoon.



The compressor clutch isn't engaging.
When I switch AC on engine rpm increases so switch is OK and ECU is responding.
Fuse OK and relay in engine compartment fuse box is pulling in when I insert it with AC switched on.
Pull plug from what I think is a pressure sensor on the small bore metal pipe at nearside of radiator and the fans start up but still the clutch doesn't engage.

So is there a fudge to get it to engage and prove whether it's a low gas pressure fault? Or could it be something else? :)

Thanks, any help appreciated
 
I don't have AC, I open the sunroof and lower the rear window instead. Could it be down to the belt that drives the compressor?

I know if you use AC with a low refrigerant level it can damage the compressor.
 
Thanks hawardo, I have removed the splash shield from the inner wing and can see the belt is OK and the outer part of the clutch/pulley is just freewheeling around the hub.
 
Hi,

As the relay pulls in I would check for live feed to compressor clutch terminal. If o.k do a resistance check between clutch terminal and compressor body if clutch windings are good I would expect about 2-4 ohms. If windings are o.k then you could bring a temporary fused live to compressor clutch terminal and check AC cooling efficiency. I'm sure that I don't need to remind you not to run AC too long with low pressure.

Good luck. Dann..
 
Dann said:
Hi,

As the relay pulls in I would check for live feed to compressor clutch terminal. If o.k do a resistance check between clutch terminal and compressor body if clutch windings are good I would expect about 2-4 ohms. If windings are o.k then you could bring a temporary fused live to compressor clutch terminal and check AC cooling efficiency. I'm sure that I don't need to remind you not to run AC too long with low pressure.

Good luck. Dann..
Click to expand...

Thanks Dann, I will do the checks you recommend if necessary but as access to the area is a right pig I was hoping to prove the compressor and clutch from a remote connection somewhere. Do you know if I can safely bridge the connections in the plug to the sensor in the pipework?

howardo said:
I'm guessing now but aside from a mechanical failure on the compresser could a refrigerant leak be the cause?
Click to expand...

Yes I'm thinking it's low pressure at the mo but thought that the efficiency would drop over time rather than it just stop. I've never had a system fail completely on me before so not sure.
 
Do you know if I can safely bridge the connections in the plug to the sensor in the pipework?
The sensor becomes open circuit when it sees sufficient refrigerant pressure in the AC circuit. So a bit of a quandry: these systems unfortunately don't incorporate the handy 'sight glass' in the drier unit which showed the presence, or otherwise of refrigerant. If you unplug the sensor and measure resistance across the pins at the moment I'm sure you'll read very low resistance which either means low refrigerant pressure or faulty pressure switch. There are lots of electrical checks you can make but in the end the only way to safely establish refrigerant charge level is with the fancy AC charging station. D..
 
I'm also guessing, but Howardo might have a point. As I think the refrigerant usually contains some form of lubricant, it would make sense for there to be a failsafe when it looses too much pressure.
Sorry, but I don't really know & hope someone can help as you've been very good to all the other forum members here.

Good Luck.
 
when I had this with a vauxhall, low pressure inhibited the clutch engaging, even when it was called for.

how much is the "gas it yourself" canister from halfrauds ?
 
Ok had to bite the bullet and get a re-gas kit with a gauge, £40 :eek: but the only way of getting any further assessment.

The pressure is high at 65psi not low. Apparently it should be about 45psi

I can't think of anything that would increase the gas pressure other than the current ambient temperatures were having. Fading sticker on the slam panel indicates an air con service or check 05/08 (I think) so I can only assume it was over filled then and now the hot weather has caused it to increase to the high pressure cut off.

Just trying to work out why it hasn't dropped overnight though.

Any further thoughts before i vent some off.
 
Well reducing the pressure made no difference at all and reading on the net the static pressure may have been ok. The coloured zones on the halfrauds gauge which made me think that it was high could be correct for when the AC is operating.

Going to get it up on stands and remove the undertray to gain access to the compressor and it's electrical connection.
 
Dann said:
Hi,

As the relay pulls in I would check for live feed to compressor clutch terminal. If o.k do a resistance check between clutch terminal and compressor body if clutch windings are good I would expect about 2-4 ohms. If windings are o.k then you could bring a temporary fused live to compressor clutch terminal and check AC cooling efficiency. I'm sure that I don't need to remind you not to run AC too long with low pressure.

Good luck. Dann..
Click to expand...

I have a live feed to the compressor windings.

Removed clutch and windings, resistance = 2.6 mega ohms.

are they available separately?
 
Yes i've changed clutches and windings, shop around on the web, sometimes you need a special puller for the clutch but as you've already got it off that shouldn't be a problem. D..
 
Chaser. I asked a similar question as I wasn't sure about low side pressure. Mine has a slow leak and needs topping up annually. It stops working when the pressures too low. Low pressure side can be anything between 45 and about 80PSI with the compressor running and 180 on the high side.
The only accurate way of getting it right is to weight the refrigerant in to an empty system. From memory its about 540grams (I think there is a sticker under the bonnet somewhere). The static pressure with the compressor not working is dependent on ambient temp.

It won't run if the pressure gets too low.

Is there any signs of oil on the pipework? This would indicate where the leak is as the oil is carried round with the refrigerant. If its lost some oil this will need topping up too. At this point I would be taking it to an A/C specialist I think.

Specialist being the word to watch. I live opposite a garage that offers "A/C repairs and Maintenance". They sort of know how to use the machine to add gas but I don't think they really know what they are doing. I used to do a/c repairs (not on cars) years ago so know a bit and when I questioned them about compressors they just looked vague!
 
tonyt37 said:
At this point I would be taking it to an A/C specialist I think.

Specialist being the word to watch. I live opposite a garage that offers "A/C repairs and Maintenance". They sort of know how to use the machine to add gas but I don't think they really know what they are doing. I used to do a/c repairs (not on cars) years ago so know a bit and when I questioned them about compressors they just looked vague!
Click to expand...


This is exactly what I have found over the last few days, lots of people trained is service and regas procedure but don't really know jack **** about how the vehicle specific system/electrics operate.
Clutch spares don't seem to be available even from the stealer so options are either to hand over £500+ for a new compressor or wait and see if a second hand clutch or complete compressor appears on fleabay.

If anyone spots a SANDEN PVX 16 pump from a TD4 after chassis 3A289510, LR part no. JPB500120 should be on the pump label, please pm me.
Cheers for everyones help so far......

Chaser.
 
Complete long shot, but would an alternator/starter motor repairer be able to redo the windings for you.
 
chromiumuk said:
Complete long shot, but would an alternator/starter motor repairer be able to redo the windings for you.
Click to expand...

Not such a long shot chromie, on Monday I went to an electrical engineering firm who willing agreed to attempt it although they were used to doing huge motors. Since it was knackered anyway I let them try.
They stripped out the old winding and discovered the internal diode and it's mounting became damaged so they didn't go any further with it.

In the meantime i have been searching around for suitable connectors to use to rebuild and secure the diode and hope to go back to them tomorrow to see if they can now rewind it.

The man in charge was a good sort, kept apologising for not being able to do it and said it had hoped to do it for free! :)
 
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