air con pump/compressor

[billskip]

Hi all

Advice wanted from an engineer who has worked on, dismantled/repaired an air condition pump/compressor.

My unit has failed and I want to strip it down and see if I can repair it.

Problem is I have not had one apart,so before attacking it with a big hammer /forums/images/graemlins/grin.gif

I wondered if any of you may have some knowledge about these units.

It is a belt driven unit (same as fitted to a car) with no name or any ID on it.

any advise please?

 

[Avocet]

Are you sure it's the compressor itself? They are normally very reliable and long-lived. I have never stripped one and, depending on age and type, there are many different designs internally. I've seen one old Sanden unit in pieces and it's a typical swashplate pump inside. I think there might be a special tool required to change the shaft seal in the nose. Probably worth just getting a recon compressor. Wouldn't mind betting it would be cheaper than trying to buy all the spares, seals and gaskets separately.

 

[billskip]

Hi Ian

Yes I am sure its the compressor.

I think you are correct looks like swash plate type,but I have only looked in the hole for the pipe connection.

It looks like aluminum and it looks very "dry" I wonder if some part has oil in it and the seal my have gone, but there is no visable sign of oil leak.

end of the day maybe best get a replacement, but I am reluctant to just pay out without trying and learning a bit myself.

Im hoping there maybe an air con man on the forum but maybe aircon dosn't pay enough to own a boat /forums/images/graemlins/grin.gif

thanks Ian

 

[Avocet]

What refrigerant are you using? IF it's R134a, that would suggest that the compressor is less than 10 years old (the older ones used R12 and that was banned (in Europe at least) some time ago. Sanden make by far the largest numbers of automotive compressors so I'd not be surprised if it was one of theirs. There should be a plate on it though. There's a bloke keeps trying to sell replacement ones for my car on Ebay:
http://cgi.ebay.co.uk/Alfa-Romeo-164-Com...1QQcmdZViewItem for not much money. I DO know that if you try to change refrigerant, you need to replace all the seals in the compressor as there are different seals for different refrigerants. What sort of symptoms were you getting?

 

[rob2]

Bill,

Ian is probably right. Although the compressor does not commonly cause the fault, it is very vulnerable to damage as a consequence of a fault. Perhaps the first thing you can check yourself is to look for leaks.
The system runs on a refrigerant gas with a compatible oil which are together pumped around the system. Therefore, if you lose the gas there's a good chance you'll also lose the oil. Reminiscent of Velocette motorbikes (If its not leaking oil - you've run out). Full flow lubrication can also mean total loss. Although you might find a major leak in the compressor, e.g. the oil seal, this may be the result not the cause and is masking a weeping joint elsewhere.
I would remove the compressor (I presume it has self sealing hoses fitted?) and check that it has no signs of overheating of the clutch, rotates smoothly by hand with the ports open and does not leak. That said, it should work! If not, it may be cheapest to source a recon unit - but thoroughly check the whole system for leaks before using. Ideally the system should be flushed and recharged, but that isn't so simple on a boat installation with precharged self sealing components.
Could you send me a photo of the compressor? I would recognise a Sanden unit. The most common choice is a wobble plate type, true swash plate units are now used in cars but are quite recent.
Is it an old R22 system or a newer R134a system? R22 is now unserviceable, so a new compressor would be cost effective, but the system must be flushed, evacuated and the correct oil/gas mixture introduced.
Any car aircon technician should be able to help you, but will probably need to get the boat to a berth where he can use a mobile charging system (always mains powered). I'm not certain, but the gas/oil ratio may be loaded to reduce the efficiency of the compressor, as it could turn the boat into an ice box at full chat! Do you know the name of the system supplier? maybe a label on some other component would give a hint?
Rob.

 

[Cliveshep]

I stripped/repaired a Mitsubishi unit on my imported Pajero. The thing had seized up after a pipe got damaged, losing oil and gas, knackered the bearings and the swash plate was also worn. Parts can be purchased for compressors, I believe a Swedish firm make them, I got mine from Hunts Auto Electrical in Huntingdon, Cambs. It is essential to replace all the "O" rings/seals, get all the reed-valve plates/spacers in the right order etc and to work in absolute cleanliness in a warm, dry environment. Any moisture left in the unit will later freeze and ice spicules will block the venturi in the condensors. Clean the outside first before stripping down, lay all the bits out in order. The unit has probably got 5 double ended pistons driven by an angled plate on a shaft, the "swash-plate". This is lubricated by the oil in the system. If it is worn the pistons "knock" as their stroke is reversed. You should purchase a new one, cost about £100, also the bearings and seals/"O" rings, not expensive. When you re-assemble the last bit fitted is the clutch which is thrown in by an electro magnet. The clearance between the clutch and the drive pulley plate is crucial as the throw of the clutch is small. If the clutch looks burnt that is normal but if the friction inserts have worn down better replace it. Adjust spacing with packer washers on the main shaft on assembly to get it right. Good luck. DIY is cheaper than purchase of a new unit by a long way but do be painstaking.

 

[billskip]

Thanks for all advice.

You all confirm my suspitions that the gass escaped somewere, and there should be some sort of lubrication.

The symptoms were that it seemed to be ok, but I had suspitions that it was not cooling as well as normal.

The temp out here (Venezuela) got a little warmer 35deg and I put it down to the unit not being able to cope.

However the compressor started to make a noise like a "dry bearing" and then stopped cooling

The unit is no more than 5yrs old but there is no plate or info on it at all, I think it is a unit as fitted to a small Daewoo car.

I will take a few pics and see if I can post them. /forums/images/graemlins/confused.gif but I can email them Ian.

Thanks to all

 

[Avocet]

Odd though - on all the car systems I've seen, they have something called a "trinary" switch on the receiver (about the size of a small beer can). The switch SHOULD prevent the compressory clutch from energising if (a) the pressure is too low and (b) the pressure is too high. It also has a third setting which turns on the radiator fan if the pressure is high so that more air is drawn through the condenser (and if that doesn't work it cuts out the compressor altogether). It is therefore very unusual for a refrigerant leak to damage a compressor because if enough refirgerant (and oil) leaks out, to risk damaging the compressor, this switch ought to prevent the compressor from turning by cutting power to the electromagnetic clutch.

Does the pulley spin freely and quietly at present? If it does, I agree your compressor is probably damaged but if it doesn't, you might get away with simply replacing the bearing the electromagnetic clutch.