MGF Air Conditioning Problem

Hi Guys, New to this site. Have a problem with my 97 MGF air conditioning. Having owned this since 2000 & being an air conditioning mechanic, I have over the journey replaced the refrigerant in the vehicle. Evacuated & weighed refrigerant R134a in each time. No leaks are evident in the system. The car suffers very high discharge pressure, 400psi plus, when stationery, but with the engine @ 3000rpm, roughly equivalent to 100kph.
I have replaced the receiver dryer & TX Valve, both to no avail. The operating pressures are 30 psi suction & 400 psi discharge at the above RPM with a 26oC ambient. The temperature from the drivers side outlet is 10oC. Added 620grams of R134a refrigerant as per the book.

At this stage I have not checked all the pipework for kinks etc or the condenser, although both fans operate& stay operating whilst the compressor is engaged. Without removing the front of the car to inspect the condenser/radiator, is there something someone can suggest where to investigate next. Is there an inherent problem with the design of the system, as it gives the impression the condenser is undersized. To operate the system out on the road, will no doubt kill the compressor or burst pipes especially when ambient/road temperatures can be well in excess of 60oC. Engine temp remains normal, half way on gauge.

The book states a variable outlet temperature between 7 > 15oC @ 26oC ambient (I think from memory), which is ordinary, especially if I compare it to my Rover 75 or my Landcruiser A/C, which are much colder in outlet temperatures.

Your ideas and thought are appreciated.

Regards Ian

Hi, Welcome to the T-bar!
My air con(when gassed) blows really nice and cold as should yours, with you being an aircon service guy, you must have more knowledge on the subject than most. I do some basic work on refrigerated systems with chiller units at work, and can only surmise if you have a pressure fault in the system, then you may have a partial blockage preventing the circulation of the refrigerant. The condenser situated in front of the radiator is more than large enough to handle the job, remember its only a two seater cockpit. Maybe its worth draining the system and making sure that you have free air flow through all the pipes, condenser and pump.
If you have your own re-gas ability, then it should be a relatively inexpensive exercise..
Good luck with the fault finding and let us know how you get on!

Now I have to get mine re-gassed, it drops the refrigerant every couple of years if I forget to use it at least once a month!

Sundance

:welcome2:
Sadly I know nothing about a/c.:nonod:

Hi and :welcome: . It's some years since I did anything on A/C but I seem to recall a similar fault where the receiver dryer was the fault as it wasn't ' new ' but a second hand item and was goosed ! You've already gone the other route with your description so I'm not much help to you .

John :nonod:

It sounds like the ECU is not getting a signal that there is high pressure in the system. Have you checked the A/C relay pack? Is the trinary switch on the dryer working, or is the wiring to the trinary switch okay? Are both fans on the condenser working? I've attached the A/C description and operation pages from the electrical manual in case you do not have them.

Whilst I've had no problems with my A/C I find it barely up to Aussie conditions, I've not tested it's pressure readings and would be interested to know if you find the condensor is too small for the job.
I find R134a needs to run at higher pressures and is no where near as effective as the old R12 stuff, a propane based refrigerant such as Hychill 30 a blend of R600a and R290 is more effective than R134a, the downside is that propane based refrigerants are of course highly flammable.

Cobber wrote: Whilst I've had no problems with my A/C I find it barely up to Aussie conditions, I've not tested it's pressure readings and would be interested to know if you find the condenser is too small for the job.

I find R134a needs to run at higher pressures and is no where near as effective as the old R12 stuff, a propane based refrigerant such as Hychill 30 a blend of R600a and R290 is more effective than R134a, the downside is that propane based refrigerants are of course highly flammable.

In terms of the operation of the system, our F's do cool the ambient air well. From what I have read, a well operating a/c system should cool the outside air by 15-20C. On a sunny day, with the ambient temperature around 25C, I have measured the air at the vents with a thermometer to be 7C, a 18C temperature difference, which is good.

On the other hand, I do agree with Cobber, the interior of the car doesn't get very cool. Here in SW Ontario, on a hot, humid summer day, it is not overly cool in the car, even though the temperature at the vent is significantly lower than the outside temperature. I think part of the problem is that you are trying to cool a black interior, with a black hood, not an easy thing. Another part of the problem is the location of the centre vents so far up on the dash. I do find operating the a/c in recirc mode does improve cooling a little bit. Something else we have found is that the condensate drain line on the bottom of the evaporator is not large enough. Both of our cars have experienced water under the carpet when the a/c has been operated all day long on humid days.

Hi and welcome to the forum

I would ask a

Willy wrote: an air conditioning mechanic,

so apart checking that everything is working I have no idea.

James