This article addresses a common issue in Freightliner trucks: an intermittently working AC compressor. After six months of troubleshooting faulty wiring in a Freightliner, the AC compressor remains a persistent problem. While the system is fully charged and functions correctly when engaged, the compressor clutch only activates sporadically. This points to a potential issue with either the AC compressor relay or a low air pressure cut-out switch.
The Elusive Compressor Relay and Low Pressure Switch
The primary challenge lies in locating these two components. The main fuse panel, while clearly labeled, lacks a designated “A/C compressor” relay socket. This raises the question: do some Freightliner models utilize a different relay location, or perhaps forgo a dedicated relay altogether? The HVAC and Hi-fan relays are functional and receive power, but they don’t control the compressor clutch. A circuit breaker marked “A/C CL” is also operational.
The truck does possess a low air AC compressor cut-out switch, preventing compressor engagement until the air pressure reaches 70 psi, likely due to a fan hub requiring positive air pressure. However, its location remains a mystery. Schematics suggest it should be attached to a constant air port on the switch manifold under the dash, but no such switch exists. Even ordering a new switch based on a parts diagram showing a clamped switch near the manifold proved fruitless. The received switch controlled the stale air timer display, not the compressor. A thorough search under the hood and around the cowl yielded no results.
Deep Dive into the Dash and Beyond
The search continues within the dash, stopping short of major disassembly. The seemingly simple task of locating these two components has become unexpectedly complex. Accessing Freightliner schematics specific to VIN A02952 could provide crucial insights. However, obtaining assistance from the local dealership has been unsuccessful.
Seeking Expert Assistance
The frustration of this ongoing AC issue is understandable. If you have experience with Freightliner AC systems, specifically models with VIN A02952, your expertise would be invaluable. Sharing knowledge on the location of the compressor relay or the low air pressure cut-out switch could provide a much-needed solution. Any insights into accessing official Freightliner schematics would also be greatly appreciated. Let’s get this AC compressor running reliably.
