Frequently Asked Questions About Mack CH/CHN/CHU Truck Heat & AC Parts

Will these HVAC parts fit my specific Mack CH model year?

Our heat and AC parts are compatible with Mack CH, CHN, and CHU models from 1988 to 2007. However, there were minor changes in mounting brackets and electrical connections starting with 2001 models. For trucks built between 2001-2007, double-check the part numbers against your original components or contact us with your VIN for exact fitment verification. Pre-2001 models typically have more universal fitment across the CH series.

What are the most common AC compressor issues and which replacement should I choose?

The most frequent problems are clutch failure, refrigerant leaks, and bearing noise. For Mack CH trucks, we recommend the Sanden SD7H15 compressor as a direct replacement for most applications. If your truck has a Seltec/Valeo TM-16 compressor, stick with that style for easier installation. Always replace the receiver-drier and expansion valve when installing a new compressor to prevent contamination and ensure warranty coverage.

How difficult is it to replace the heater core, and what tools do I need?

Heater core replacement typically takes 4-6 hours and requires dash panel removal. You'll need basic hand tools, trim removal tools, and a coolant drain pan. The main challenge is accessing the HVAC box behind the dash. Many technicians report that disconnecting the steering column (without fully removing it) provides much better access. Be prepared to replace the foam seals around the heater box during reassembly to prevent air leaks.

Why is my blower motor running but producing weak airflow?

This usually indicates a clogged cabin air filter or debris in the evaporator core. Mack CH trucks have the cabin filter located behind the glove box, which should be replaced every 12 months. If airflow remains weak after filter replacement, check the blower motor resistor - these commonly fail and cause reduced fan speeds. The resistor is mounted on the HVAC box and can be accessed from under the dash on the passenger side.

What's included in a complete AC retrofit kit, and is it worth upgrading from R-12?

A complete R-134a retrofit kit includes new O-rings, compressor oil, retrofit fittings, pressure switch, and refrigerant oil. For Mack CH trucks originally equipped with R-12, retrofitting is recommended as R-12 is no longer produced. The conversion typically improves cooling performance and reduces maintenance costs. Most CH models require 2.5-3 pounds of R-134a after conversion, compared to the original 3.5 pounds of R-12.