Engine - No Start/Fully Discharged Battery
File In Section: 6 - EngineBulletin No.: 57-64-05
Date: September, 1995
Subject:
No Start, Battery Fully Discharged
(Replace Primary Cooling Fan Relay - Install New PROM)
Models:
1995 Chevrolet Lumina, Monte Carlo
1995 Oldsmobile Cutlass Supreme
1995 Pontiac Grand Prix
with 3.4L Twin DOHC Engine (VIN X - RPO LQ1)
Condition
Some owners may experience a no start condition due to a discharged battery.
Cause
The discharged battery condition is due to the primary cooling relay contacts welding. When this happens, the cooling fan continues to run until the battery is fully discharged. The contacts weld when the engine is shut off with the A/C compressor clutch being engaged before the PCM activates the primary fan relay. The A/C clutch drives all ignition 1 devices to a negative voltage. This negative voltage causes the PCM to energize the cooling fan relay. In a very short period of time, there is a high in-rush of current to the cooling fan. The welding of the relay contacts occurs when the relay deactivates when a very high in-rush of current is present.
Correction
After following standard procedures for diagnosing a fully discharged battery and it is determined that the primary cooling fan relay contacts are welded, it will be necessary to replace both the relay and install a new PROM. The new PROM changes the calibratible value for minimum A/C compressor head pressure from approximately 190 psi to 42 psi. This insures that the cooling fan will be operational during any period when the A/C system is in operation.
Parts Information
Parts are currently available from GMSPO.
Warranty Information
For vehicles repaired under warranty, use:
Labor Operation Labor Time
J6364 Prom, PCM - Replace 0.7 hr
N2850 Relay, Primary Cooling
Fan - Replace Use published labor operation time.