[W126 Coupe] Air Conditioning Diagnosis

[Dick Spellman]

Dan Landiss wrote:

> on 6/11/2007 6:57 PM Dick Spellman wrote:

>> Please view this link and dependent on the refrigerant you are using 

>> (please let me know) see if your 25psi reading was in spec for 90F 

>> outside on the day you tested low pressure.  Also was the car at idle 

>> or at 1200-1500 rpm when testing?

>

> R12, about an 80F day so the pressure could have been lower. To pull 

> it down that far require raising the RPM to maybe 1500.

>

>> If you can, let me know what the engine coolant was reading too and 

>> when was visco clutch last replaced (miles) and did the electric fan 

>> ever kick on???

>

> Normal coolant, I don't think the electric fan came on (will it, with 

> the bonnet raised?)

>

>> Does compressor stay engaged over say a 10 minute period or is it 

>> cycling on and off with frequency? 

>

> Stays engaged.

>

Dan:

With the cooling system working perfectly but, the low side pressure 
being a bit higher than it should be, (i.e., a normal 18 at 80 vs. your 
25 at 80) I'd now be very curious to see what the high side pressure 
relationship is the next chance you get to take a reading.  My thoughts 
are that either the expansion valve is stuck open or that the compressor 
is weak or you've been running with a slight overcharge all of this 
time.  I think you need to confirm the refrigerant gear is all in 
perfect working order and perhaps check the vacuum element conditions as 
well.  Depending on your diy capabilities the easiest (believe it or 
not) maybe the vacuum elements on that recirc. flap first.  Then failing 
an adequate vent temp, finding a decent shop to do the refrigerant 
circuit diagnoses.

One other question, do you see a difference in vent temps while driving 
at 30mph (10 minutes) vs. highway (10 minutes) vs. at idle in drive (1-2 
minutes)?

Dick