1975 Ford ThunderbirdFACTORY OEM SERVICE PROCEDURE

Compressor Output Test

  1. Turn climate control system off, if equipped. Place transmission in "N", and run engine until fast idle screw is off fast idle cam. Turn engine off. Release compressed air in system, using tire-type bleed valve at compressor. Remove high pressure line at compressor, and attach suitable test gauge (T68N-5A681-B). Start engine. Pressure should build to 60-90 psi in a few seconds. If this pressure is not observed, race engine a few times to build pressure.
  2. If compressor fails to function, check rubber vacuum line for obstructions and proper connections. If compressor still fails to function or if compressor output is low, the distributor valve pivot screw may be loose or compressor may need servicing. See SERVICING  in this article.
  3. Turn engine off. Observe test gauge reading for evidence of compressor air leak. If air leak is present, apply leak detector fluid at all connections and at diaphragm between 1st and 2nd stage housings. Tightening of housing through-bolts may correct diaphragm leak. Correct leaks by tightening screws and connections, or by replacing parts.
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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