Greg,
I can confirm there is no orifice tube if your dash AC is still stock. It
may not be, for one never knows what has happened over the past twenty five
years.
These units came from factory with a thermostatic expansion valve instead of
orifice tube. It is located on the evaporator and visible when you pull the
front cover off the big black AC / heater box.
There is a finger screen in the expansion valve inlet port which can be
checked, but I would think the receiver dryer fine mesh screen would
normally trap any residue before it gets to this expansion valve screen.
When replacing a compressor only, a good shop will measure how much oil
drains from the old compressor and install a new compressor containing that
same amount of new oil.
Since you are not sure how much oil is in your system, an alternative is
flush your system to get rid of all the old oil. Replace your dryer, drain
the compressor oil (whether new or old) and fill with 10.5 ounces of new
oil.
The system normally has 3.5 lbs. of R12. With this amount of freon,
pressures should be within the ball park if all is working well.
The entire system normally contains 10.5 ounces R12 oil.
The GMCMH maintenance manuals and parts book, available from Cinnabar,
have very detailed information on proper dash AC maintenance.
Don Miller
Shenandoah Valley of Virginia
> Help! When i bought my GMC back in October, i knew that the dash AC had
not
> been operational for a while, and the compressor was diagnosed as the
> problem...
I can confirm there is no orifice tube if your dash AC is still stock. It
may not be, for one never knows what has happened over the past twenty five
years.
These units came from factory with a thermostatic expansion valve instead of
orifice tube. It is located on the evaporator and visible when you pull the
front cover off the big black AC / heater box.
There is a finger screen in the expansion valve inlet port which can be
checked, but I would think the receiver dryer fine mesh screen would
normally trap any residue before it gets to this expansion valve screen.
When replacing a compressor only, a good shop will measure how much oil
drains from the old compressor and install a new compressor containing that
same amount of new oil.
Since you are not sure how much oil is in your system, an alternative is
flush your system to get rid of all the old oil. Replace your dryer, drain
the compressor oil (whether new or old) and fill with 10.5 ounces of new
oil.
The system normally has 3.5 lbs. of R12. With this amount of freon,
pressures should be within the ball park if all is working well.
The entire system normally contains 10.5 ounces R12 oil.
The GMCMH maintenance manuals and parts book, available from Cinnabar,
have very detailed information on proper dash AC maintenance.
Don Miller
Shenandoah Valley of Virginia
> Help! When i bought my GMC back in October, i knew that the dash AC had
not
> been operational for a while, and the compressor was diagnosed as the
> problem...
