Coupe GT A/C

["R. Cummings" <cumm@flash.net>]

To: Allan Jones
Re: 86 Coupe GT A/C questions

After 2 years, I don't think the shop will repair your system for free but
they will probably diagnose it at no charge.

Dye is generally not put in refrigerants. There is no federal law requiring
it and I have not heard of any state and local laws requiring it. The new
flourescent dye is not so bad but there was a red dye on the market some
years ago and it would make a terrible mess under the hood. The dye is
carried in the refrigerant oil not in the refrigerant itself. Compressor
shaft seals always leak a little, which keeps the seal lubricated.

The system must be checked with a sniffer anyway. Dye really doesn't take
the place of a skilled mechanic.

The Coupe runs high head pressures. I have had to replace the receiver/dryer
twice because of leaks around the melt plug (a safety device in the receiver
that melts if the temperature gets too high). That and "o" ring leaks are
the biggest offenders.

It is unusual for the evaporator in the Coupe to develop a leak. It is a
very robust tube and fin construction. This cannot be said of the brazed
aluminum plate fin evaporators used by GM, Ford and also by Audi in many
applications. Sounds from other e mails to be a difficult job to replace.

To check for evaporator leaks the system needs some refrigerant and is
turned off for 15 minutes. The sniffer is put into a floor air outlet
beneath the instrument panel. Make sure the control directs air to the floor
mode. Turn the key on and let the blower run on low. If the evaporator is
leaking, the sniffer will detect the refrigerant that has collected and is
now coming out the outlet.

Once the refrigerant is removed, anyone can work on the system and replace
the components.

The most important thing to remember is that the shop has to fix the problem
that caused the system to lose charge in the first place. This may not only
be a leak but also some other failed component like the switch that turns
the fan on at high head pressure.

Most repeat returns are due to fixing the symptoms but not finding the root
cause of the problem.

Good luck.

Bob Cummings
87 Coupe GT