Aircon Queries.

[Guest paco929]

H i everyone,

Thanks for the help with my previous problem, namely fuel injection pump. Now OK.

This time its the aircon. I bought the car when it had been standing for about six months. It probably needs a re-gas. My main query is . My instrument panel does not have an outside temp guage. Nor does the passenger mirror have an outside temp sensor. My car is a 1997 2.1 td Did these earlier aircon models not have this temp guage ? or has this car been got at !! Everything else seems kosher ie: Air con control and switch are in place. Just an additional point though. The illumination on the aircon switch comes on when switched on, but is very dim. Don't know if this is significant .

Appreciate any pointers,

Jack.

[Guest Colin Hunter]

Is The car a late Mk1 or early Mk2? The changeover was sometime in '97 or '98 I think. The difference externally is in the bonnet/grill area. Is the grill separate from the bonnet (Mk1) or integral (Mk2)? If it's a Mk1 I don't think it will have an outside temp indicator. I had 2 Mk1s and neither did, although they were only LX's. However my present Mk2 LX has the temp readout next to the clock. The outside temp readout has nothing to do with the operation of the aircon. It's just a readout!

 

It's very likely that during the car's layup period the gas has escaped. Citroen reccomend operating the system at least once a week to keep the seals and other components in good order. If the pump seals have "dried up" the gas may have escaped there. The only way to find out is to try to get it re-gassed.

 

What happens is that the car is coupled to a machine which is programmed to the system's requirements of gas and oil. The machine then pumps out any gas/oil remaining in the system and reclaims it. The system is then pumped down to a vacuum to remove air/moisture. When a full vacuum is acheived the pump cuts out, and if the system maintains a vacuum for a set period, the machine will allow the system to be charged with the relevant amount of gas & oil. If the machine senses that the vacuum is not being held (Indicating a system leak) it shuts down and the operator knows there is a problem.

 

The system can then be pressurised with a fluid containing "Fluerescene", A green substance which reacts to UV light, and the leak traced by shining said UV light source around the system pipes and components until the leak shows up.

 

Not sure if the brightness of the indicator has any bearing on the operation of the system. Best bet is to phone round your local area for aircon specialists and get it checked out. I imagine they'll be quite happy to see you at this time of year!

 

Cheers. Hope this helps. :D

[willie]

Is The car a late Mk1 or early Mk2? The changeover was sometime in '97 or '98 I think. The difference externally is in the bonnet/grill area. Is the grill separate from the bonnet (Mk1) or integral (Mk2)? If it's a Mk1 I don't think it will have an outside temp indicator. I had 2 Mk1s and neither did, although they were only LX's. However my present Mk2 LX has the temp readout next to the clock. The outside temp readout has nothing to do with the operation of the aircon. It's just a readout!

 

It's very likely that during the car's layup period the gas has escaped. Citroen reccomend operating the system at least once a week to keep the seals and other components in good order. If the pump seals have "dried up" the gas may have escaped there. The only way to find out is to try to get it re-gassed.

 

What happens is that the car is coupled to a machine which is programmed to the system's requirements of gas and oil. The machine then pumps out any gas/oil remaining in the system and reclaims it. The system is then pumped down to a vacuum to remove air/moisture. When a full vacuum is acheived the pump cuts out, and if the system maintains a vacuum for a set period, the machine will allow the system to be charged with the relevant amount of gas & oil. If the machine senses that the vacuum is not being held (Indicating a system leak) it shuts down and the operator knows there is a problem.

 

The system can then be pressurised with a fluid containing "Fluerescene", A green substance which reacts to UV light, and the leak traced by shining said UV light source around the system pipes and components until the leak shows up.

 

Not sure if the brightness of the indicator has any bearing on the operation of the system. Best bet is to phone round your local area for aircon specialists and get it checked out. I imagine they'll be quite happy to see you at this time of year!

 

Cheers. Hope this helps. :D

 

A wealth of information is our Colin!!!!

[Guest paco929]

Thanks again Colin. .Really appreciate your help. I was hoping that I would get a reply roughly saying what you have said. The car is a December 1997 Mk 1. ie separate grill and bonnet. I suppose this system is pre gizmos like dash temp guages etc. I was a bit worried that I had a problem with the compressor clutch, which was not driving the compressor. Until I read in another listing about the pressure switch which has to be made for the clutch to engage. I linked the terminals in the plug, and he presto the clutch engaged. I just have to hope now that the seals are not knackered.

Next step is gas it up and hope for the best !!

Best regards,

Jack.

 

P.S. Yes I must agree Willie. It's a good job someone knows what they are talking about !!

[Guest Colin Hunter]

Once more chaps, thanks very much for the compliments. You must remember that I am an Engineer by profession and cars are only machines when all is said and done.

 

Aircon systems are just the same as your fridge or freezer in your house, and, indeed, operate on the same principle as the refigeration systems I worked on when I was at Sea and brought New Zealand Lamb and Australian Beef to the UK table. Not to mention Bananas and Kiwi fruits and other exotic fruits which would have rotted to Buggery if not for the magic of refrigeration!

 

You basically have a system containing a volatile gas, a compressor, a condenser, a thermal expansion valve and an evaporator. The condenser is in the radiator area, and the evaporator is inside the car near the heater matrix.

 

What basically happens is that you have a high pressure and a low pressure side to the system. The gas flows to the compressor where it is pumped up to a higher pressure (Energy added) It then flows through the condenser where it becomes a liquid at the same high pressure. It then passes through the contolling part of the system, the expansion valve, which controls the amount of gas needed to maintain the set temperature. as the liquid passes through the valve it enters the low pressure side of the circuit and as it does so it will absorb heat (Energy released) from the surroundings to complete the change of state from liquid to gas. It does this in the Evaporator which is the bit that cools the car when you turn on the aircon. The gas then flows back to the compressor, etc, etc!

 

If the temperature inside the car drops below the setpoint the expansion valve will close and the compressor will "pump down" untill the low pressure switch cuts it out. It will cut in again when required. This is why you probably won't get a system which is short of gas to run. The pressure required by the system to operate won't be there and the clutch won't go in.

 

This is not just for citroen aircon systems, it is the basis upon which EVERY refrigeration system operates!

 

As I always say, think basics and you'll get there!

 

Cheers lads :D