I recently purchased a 1988 Mazda RX-7 from the original owner. The car is in exceptional shape, with the exception of the air conditioning system, which doesn’t work at all.

I’m particularly wary of taking the car into the shop for repair, because it is mostly a hobby and usually sits in the garage. However, the car is a joy to drive, just not in South Bay weather. I was hoping you could give me a general idea of what it might cost for a rebuild of this type.

Corey Jahns, San Jose, Calif.

It would be tough to say for sure what it will take to restore the RX-7’s A/C system, but I can describe a few inspections for you to perform, then we can go from there.

Let’s start by checking the air distribution system for proper operation. Does it change modes, blowing air properly from the dash vents, heater and defroster ducts? If not, work will be needed here, in addition to restoring the refrigeration system to operation.

Next, with the engine off and the keys in your pocket, try rotating the center hub of the air conditioning compressor by hand. This is a belt-driven device a bit smaller than a football, with two hoses connected to it. If the compressor turns with firm effort, yet fairly smoothly, that’s good. If not, replacement of this expensive part might be necessary.

Let’s continue by inspecting the hoses and their fittings connecting the compressor to the condenser – just ahead of the radiator – and evaporator. The hose will disappear through a grommet into the right side firewall. If the hoses and fittings are clean and dry, they’re probably OK. If signs of previous wetness or localized dirty areas are evident, refrigerant and lubricant leakage has occurred.

Assuming the above inspections are OK, your RX-7 is a good candidate for professional refrigerant leakage testing, renewal of perhaps an O-ring seal or two, replacement of the receiver-drier, evacuation, conversion to the much less expensive and more environmentally friendly R-134a refrigerant and recharging.

It’s important to locate and repair any detectable leakage, such as faulty seals or hoses, in order to avoid repeated future recharging and harm to the environment. The receiver-drier, a circular metal container containing moisture-absorbing desiccant, should be replaced/upgraded, as it’s probably saturated.

That will ensure compatibility with the new refrigerant. Conversion to R-134a refrigerant involves removing any remaining R-12 refrigerant, installing new service fittings and adding compatible refrigerant oil.

Some compressor models, which contain Viton rubber seals, are incompatible with R-134a refrigerant and will require replacement.

Your best-case scenario will probably run around $200 to $400. Worst case, involving replacement of the compressor and/or other parts, could push the repair cost as high as $700 to $900.

Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose.

News (San Jose, Calif.).

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AP-NY-08-19-05 0617EDT