4200 Aircon Issue

C

Carrera

Junior Member
Messages
102
Hi all

I have just purchased a 4200 GT and have noticed the aircon is not working. The fan works but no cold air. The seller says it just need a re-gas because it has been getting less effective over a number of years. My question is - is that likely to be the case and if not what is the most likely cause and how easy would it be to fix? Any help much appreciated.
 
CatmanV2

CatmanV2

Member
Messages
48,806
Carrera said:
Hi all

I have just purchased a 4200 GT and have noticed the aircon is not working. The fan works but no cold air. The seller says it just need a re-gas because it has been getting less effective over a number of years. My question is - is that likely to be the case and if not what is the most likely cause and how easy would it be to fix? Any help much appreciated.
Click to expand...

It's certainly a reasonable place to start, check the gas fill

C
 
mowlas

mowlas

Member
Messages
1,736
You can do a visual inspection of the AC compressor’s front end mechanicals in terms of:
  1. Does the pulley spin and rotate OK, any noises?
  2. Is the clutch there (sometimes the bolt can come loose, and the clutch can fall off)
  3. Does the clutch engage and spin with the pulley when you put the AC on, and stop spinning when you switch it off?

Also any intermittent or constant rattling noises coming from the AC area?

www.eurospares.co.uk

Air Conditioning System Parts Diagram for the Maserati 4200 Coupe

Exploded air conditioning system parts diagram for the Maserati 4200 Coupe
www.eurospares.co.uk www.eurospares.co.uk
 
C

Carrera

Junior Member
Messages
102
Thanks guy's very useful stuff. I have not picked the car up yet so can't do any visuals. My worry is that if it is not a simple re gas it could be an expensive repair that I have not factored into the purchase price.
 
Zep

Zep

Moderator
Messages
9,289
There are quite a few reasons why it might not be working, but you are going to start with the most obvious given the symptoms, the gas. If there is some gas it, it when it’s recovered, just not enough for it to work, then it’s likely what you’ve been told is right.

As Phil says, do change the drier, they are cheap and a blocked one would be a pain if you have to take the gas back out.
 
Andy4200

Andy4200

Member
Messages
143
Yes, there are cheaper alternatives. This is what I fitted to mine, fitted and worked perfectly. It's an Alfa 166 part I seem to remember.
I think it was about £15 on ebay.
 

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hladun

hladun

Member
Messages
149
The first step is to have an AC shop draw a vacuum and see if there are leaks. If no leaks then you need 2.4 lbs of R134a (a lot). It's a sealed system so dryer changes are probably unnecessary unless it's been opened or new parts installed. It's not a Buick so it's "comfortable" at best (compressor and evaporator are too small).

P.S. Forgot you may be none NA. Charge for Euro spec is much less because of small condenser.
 
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Andy4200

Andy4200

Member
Messages
143
Yes, euro spec is 750g of refrigerant.
It does seem a fairly effective system when everything is working.
Having rebuilt most of mine I was recording central vent temps down to 3.5 degrees c.
 
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Zep

Zep

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hladun said:
The first step is to have an AC shop draw a vacuum and see if there are leaks. If no leaks then you need 2.4 lbs of R134a (a lot). It's a sealed system so dryer changes are probably unnecessary unless it's been opened or new parts installed. It's not a Buick so it's "comfortable" at best (compressor and evaporator are too small).

P.S. Forgot you may be none NA. Charge for Euro spec is much less because of small condenser.
Click to expand...

Sorry, but what you are advising may have worked for you, but it’s not good practice and can result in poor performance.

The filter / drier is there because there is a risk of contaminants. Mainly because no vacuum is perfect, so some moisture is always left and because it is a mechanical system subject to wear so further contaminants are produced in use. After a few leaks and recharges the desiccant in the drier is basically spent and causes a restriction in flow. This is even more likely if the system is left open during repair (these cars are getting old so this is more likely) the desiccant in the drier can become saturated with the same effect. It’s cheap and simple to do and will make a serious improvement to the operation of the system.

For leak testing, it is far more effective to pressurise to the max operating pressure with dry nitrogen, a vacuum can at best test the seals to 1 bar pressure, where as it operates at up to 20 bar. The nitrogen also has a lower molecular weight than the refrigerant, so if it holds nitrogen pressure without dropping then you can be confident there are no leaks. This isn’t common practice in automotive AC, but a good AC specialist will do this.

As the OP bought a car with what appears to be little or no refrigerant in it, the above is best practice. The recharging of a working system wouldn’t require all of these steps.
 
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Scaf

Scaf

Member
Messages
6,591
Zep said:
Sorry, but what you are advising may have worked for you, but it’s not good practice and can result in poor performance.

The filter / drier is there because there is a risk of contaminants. Mainly because no vacuum is perfect, so some moisture is always left and because it is a mechanical system subject to wear so further contaminants are produced in use. After a few leaks and recharges the desiccant in the drier is basically spent and causes a restriction in flow. This is even more likely if the system is left open during repair (these cars are getting old so this is more likely) the desiccant in the drier can become saturated with the same effect. It’s cheap and simple to do and will make a serious improvement to the operation of the system.

For leak testing, it is far more effective to pressurise to the max operating pressure with dry nitrogen, a vacuum can at best test the seals to 1 bar pressure, where as it operates at up to 20 bar. The nitrogen also has a lower molecular weight than the refrigerant, so if it holds nitrogen pressure without dropping then you can be confident there are no leaks. This isn’t common practice in automotive AC, but a good AC specialist will do this.

As the OP bought a car with what appears to be little or no refrigerant in it, the above is best practice. The recharging of a working system wouldn’t require all of these steps.
Click to expand...
It’s almost as if you know what your talking about :D
 
hladun

hladun

Member
Messages
149
I'd be concerned about pressurising the system to max operating pressure with nitrogen . The LP side (evaporator, LP hoses and compressor inlet) never operate at those pressures...maybe 100psi (7 bar) at most. Sounds a bit like "ball peen hammer" auto repair too me.

As for dryers, I agree that any time you open the system changing the dryer makes sense, and that assumes you're careful to keep the system clean and dry while it's apart. I've never seen a car manufacturer maintenance schedule that recommends regular dryer replacement? As for regular replacement, I'm from the school that if it ain't broke don't fix it.
 
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Zep

Zep

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9,289
Terminology issue. MOP is based on the rating of the components in the system.

I’ll raise the issue of “Ball Peen Hammer Repairs” at my next Institue of Refrigeration meeting and get back to you.
 
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