Frequently Asked Questions About Peterbilt 359 AC Driers & Compressors

What years do these AC driers and compressors fit on a Peterbilt 359?

Our AC driers and compressors are designed to fit Peterbilt 359 models from 1967 through 1987. However, there were minor variations in mounting brackets and hose connections between early models (1967-1975) and later models (1976-1987). When ordering, please have your VIN or year ready so we can ensure you receive the correct mounting hardware and fittings for your specific truck.

How difficult is it to install a new AC compressor on my 359?

Installation typically takes 2-4 hours for someone with basic mechanical skills. You'll need standard hand tools, a manifold gauge set, and a vacuum pump. The most challenging part is usually accessing the mounting bolts behind the engine accessories. We recommend having the system evacuated by a professional before removal and properly recharged after installation. Many customers report that removing the passenger side fender liner provides much better access to the compressor mounting area.

What's the difference between OEM and aftermarket driers, and which should I choose?

OEM driers use the exact specifications as original Peterbilt equipment, including aluminum housing and molecular sieve desiccant rated for R134a or R12 systems. Aftermarket options typically use steel housing and may have different port configurations. OEM driers cost 30-40% more but offer exact fit and typically last 5-7 years. Aftermarket driers work well for most applications and cost less, but may require adapter fittings. For show trucks or restorations, we recommend OEM. For working trucks, quality aftermarket brands like Four Seasons or UAC provide excellent value.

My AC system was converted from R12 to R134a - do I need special components?

Yes, converted systems require specific components. You'll need a drier with XH-7 or XH-9 desiccant compatible with R134a and PAG oil. The compressor should have barrier hoses and updated seals rated for R134a's higher operating pressures. Many of our compressors are dual-compatible, but the drier must match your refrigerant type. If you're unsure about your system, look for green service port caps (R134a) or black caps (R12). We stock conversion kits that include the correct drier, O-rings, and port adapters.

How do I know if my AC compressor is failing versus other AC problems?

Common signs of compressor failure include: loud grinding or squealing when the AC clutch engages, the clutch not engaging at all, metal shavings in the refrigerant oil, or the compressor seized/belt slipping. Before replacing the compressor, check that the clutch is receiving power and the system has proper refrigerant charge. A simple test: with the engine running and AC on max, the clutch should cycle on/off every 5-15 seconds. If it's constantly engaged or never engages, further diagnosis is needed. About 40% of "bad compressor" cases are actually electrical issues or low refrigerant.