Frequently Asked Questions About Peterbilt 357/378 AC Driers & Compressors

What year models of Peterbilt 357 and 378 are these AC driers and compressors compatible with?

Our AC driers and compressors are designed to fit Peterbilt 357 models from 1987-2007 and Peterbilt 378 models from 1986-2007. However, compatibility can vary based on your specific engine configuration and whether you have factory AC or an aftermarket system. We recommend checking your current compressor's part number or calling our tech support team at 1-888-875-7787 with your VIN to ensure proper fitment.

How difficult is it to replace the AC drier and compressor myself, and what tools will I need?

Replacing these components requires intermediate mechanical skills and typically takes 3-4 hours. You'll need basic hand tools, a manifold gauge set, vacuum pump, and refrigerant recovery equipment. The most challenging aspects are properly evacuating the system, ensuring correct belt alignment, and achieving proper refrigerant charge. Many customers opt for professional installation to avoid potential issues with warranty claims or improper charging that could damage the new components.

What's the difference between OEM and aftermarket AC compressors for my Peterbilt?

OEM compressors (typically Sanden or Red Dot) offer exact fit and proven reliability but cost 30-40% more than aftermarket options. Quality aftermarket units from brands like UAC or Four Seasons provide good performance at a lower price point, though they may have slightly different mounting brackets or hose fitting angles. Both options typically include the same warranty coverage (1-2 years), but OEM parts often have better availability of rebuild kits down the road.

How often should I replace the AC drier when changing the compressor?

You should always replace the AC drier when installing a new compressor - it's not optional. The drier removes moisture and contaminants from the system, and a saturated or contaminated drier is often what caused the compressor failure in the first place. Skipping this $30-50 component to save money will likely result in premature failure of your new compressor and void most warranties. Additionally, replace the expansion valve and flush the entire system for best results.

Why is my new AC compressor making noise or not cooling properly after installation?

Common causes include incorrect refrigerant charge (over or under-filled), air in the system from improper evacuation, wrong type of refrigerant oil, or belt tension issues. Noise specifically can indicate a faulty clutch bearing, misaligned pulleys, or internal damage from running without proper lubrication. Before assuming the compressor is defective, verify you used the correct PAG oil type and amount (usually 6-8 oz), achieved proper vacuum (under 500 microns for 30 minutes), and charged to manufacturer specifications using both high and low pressure readings.