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1991 Cadillac Sedan deVille
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530 Posts
Discussion Starter #1
I have decided to sell my '91 DeVille and thought I would charge the A/C before selling. My mechanic said that the thing probably leaked down due to selling for a couple of years. It was serviced in 2010, converted to R134a.

I bought a large can of R134a and charged the system today and it says it is full (and it is not overfull). Now the "service A/C light" is illuminating when it is calling for the A/C to run, just as it was before. Basically I can only imagine that the compressor is bad? For this car to only have 61k original miles, it has had a lot of parts go bad that most cars can go well over 100k without replacing. (That is one reason I am selling).

I didn't think until just now to look in the service manual I have to see if there is some sort of diagnostic I can run to see what the issue may be. Surely there is? I will look in the book tomorrow.

Thanks.
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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86,781 Posts
How do you know it is "full"? The system will tell you when it is low, but not when it is full.

Have you pulled the DTC's?
Did you clear the low refrigerant code before you tried to add coolant?
 

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Registered
1991 Cadillac Sedan deVille
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530 Posts
Discussion Starter #3
There is a gauge on the can of coolant. When first connected, it showed none was in it... we pushed the button and put it in there... then it said "FULL" on the gauge.

Haven't tried pulling any codes... as mentioned above I didn't think about that until I had posted this. Do those have to be cleared before adding coolant?

Thanks.

How do you know it is "full"? The system will tell you when it is low, but not when it is full.

Have you pulled the DTC's?
Did you clear the low refrigerant code before you tried to add coolant?
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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19,261 Posts
There is a gauge on the can of coolant. When first connected, it showed none was in it... we pushed the button and put it in there... then it said "FULL" on the gauge.

Haven't tried pulling any codes... as mentioned above I didn't think about that until I had posted this. Do those have to be cleared before adding coolant?

Thanks.
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I bought a large can of R134a
what size can?
your system takes around 2.2 pounds - 36oz - of freon -

There is a gauge on the can of coolant
those are SLIGHTLY better than totally useless -

it showed none was in it.
maybe -

we pushed the button and put it in there...
then it said "FULL" on the gauge.

like I said - that gauge is pretty much useless -

the AC must be working - and ON -
so the compressor can "suck" freon from the can -
and pump into the system -

operating pressures are around 30 to 35 psi on the low side -
and around 225 to 250 psi on the high side -
depending on ambient temperature -

Do those have to be cleared before adding coolant?
there are both high pressure and low pressure sensors in the system -

the high pressure sensor is there to protect the system -
the low pressure sensor is there to protect the compressor -

if the system was low - and a code was set -
the compressor is disabled -
and will not engage until the code is cleared -
 
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