Peterbilt 357/378 Heat & AC Parts

Frequently Asked Questions About Peterbilt 357/378 Heat & AC Parts

What years do these heat and AC parts fit for Peterbilt 357 and 378 models?

Our heat and AC parts are designed to fit Peterbilt 357 models from 1987-2004 and Peterbilt 378 models from 1986-2007. However, some components may have specific year breaks due to design changes. For example, blower motor assemblies changed in 1994, and evaporator cores were redesigned in 1998. Always check the specific part listing for exact year compatibility or contact our support team with your OEM for verification.

Are aftermarket AC compressors as reliable as OEM parts?

Quality aftermarket AC compressors can match OEM performance when sourced from reputable manufacturers. We carry both new aftermarket and remanufactured options that meet or exceed OEM specifications. Key differences include warranty coverage (typically 1-2 years for aftermarket vs. 3 years for OEM) and price (aftermarket options are usually 30-50% less expensive). Many drivers report excellent results with aftermarket compressors, especially brands like Sanden and Red Dot that specialize in heavy-duty truck applications.

What are the most common installation challenges with heater cores and evaporators?

The biggest challenge is accessing these components behind the dash, which typically requires 4-6 hours of labor. Common issues include: disconnecting the steering column, removing multiple dash panels without breaking clips, properly sealing new O-rings to prevent leaks, and ensuring proper coolant/refrigerant evacuation before removal. We recommend having a service manual on hand and allowing a full day for DIY installation. Many customers find it worthwhile to replace both the heater core and evaporator at the same time to avoid repeating the dash removal process.

How do I know if I need R12 or R134a AC components?

Peterbilt 357/378 trucks manufactured before 1994 typically used R12 refrigerant, while 1994 and newer models use R134a. Look for a label under the hood or on the AC compressor indicating refrigerant type. Key differences: R12 systems use mineral oil and have different pressure specifications, while R134a systems use PAG oil. If converting from R12 to R134a, you'll need a conversion kit including new O-rings, receiver-dryer, and proper oil. Mixing components between systems can cause immediate failure.

What's the difference between standard and heavy-duty blower motors?

Standard blower motors typically draw 15-20 amps and are suitable for most applications. Heavy-duty motors draw 25-30 amps and provide approximately 30% more airflow, making them ideal for extreme climates or drivers who need maximum cooling/heating performance. Heavy-duty units feature sealed bearings, thicker windings, and reinforced housings for longer life (typically 150,000+ miles vs. 100,000 for standard). The mounting dimensions are identical, but heavy-duty motors may require upgrading the blower motor resistor and ensuring your electrical system can handle the increased load.