Heater Core - Position Causes Poor Heater Performance
90chevy17Number: 90-153-1A
Section: 1A
Date: January 1990
Corp. Bulletin No.: 031101
Subject: INADEQUATE HEATER PERFORMANCE - HEATER CORE POSITION
Month and Year: 1990 W CARS
FIGURE 1:
FIGURE 2:
FIGURE 3:
Comments on the above vehicles about heater performance such as slow to warm up or never warms up may be received from some customers.
If the heater system is operating properly and engine temperature is in the operating range, the cause of the problem may be that the heater core has been pushed out of its proper position, see Figures 1 and 2. This misposition of the heater core allows the outside cold air to by-pass the core and enter the vehicle through the heater outlets.
This condition is compounded if the vehicle does not have the latest new heater outlet, as referred to in Dealer Service Bulletin No. 90-152-1A and shown in Figure 3 of this bulletin.
To address this condition use the Service Manual Procedure on the removal of the heater core cover. If the core is out of positon as shown in Figure 2 reposition the core and install the heater core cover. If the HVAC module has the old heater outlet, as shown in Figure 3, it would be advisable to install the new heater outlet as specified in Dealer Service Bulletin No. 90-152-1A.
Use the applicable Labor Operation and Time.