6000 V6-173 2.8L (1988)
Radiator Cooling Fan Motor Relay: Technical Service Bulletins
Cooling Fan - Runs Battery Dead
COOLING FAN RUNS BATTERY DEAD (DIAGNOSTIC PROCEDURE)
1984-90 6000 AND 87-90 BONNEVILLE
This bulletin cancels and replaces bulletin 90-6-29 issued 4/90. This bulletin is being revised to make corrections to second and third paragraphs.
If the above mentioned condition is encountered, and the cooling fan relay is found to have failed (the contact points sticking together), the cause may
either be in the air conditioning system or the cooling fan temperature switch.
If the cooling fan motor is found to be operating within acceptable current draw limits (20 amps on low speed or 35 amps on high speed), start by
checking the air conditioner high side pressure with the system operating. The high side pressure should be stable. If the high side shows a rapidly
vibrating needle on the gauge, this will cause the A/C cooling fan pressure switch to cycle on and off as rapidly as the gauge needle is moving. This in
turn will cause the relay contacts to arc and eventually weld themselves together leaving the fan in operation with the ignition key turned off. Sometimes
this can be further identified by tapping the relay during the failure mode and seeing the fan turn off.
A defective fan pressure switch or an internal problem in the A/C system may cause this type of failure.
Another cause of the relay failing may be a defective cooling fan temperature switch. This can be identified in the following manner. Using a test light
hooked to the positive battery terminal, touch the other end of the light to the temperature switch located on the intake manifold. With the engine
running, if the test light is found to flicker on and off rapidly, the temp switch may be causing the relay to fail in a similar manner as the failure described
above. Once the cause of failure is identified and repaired, the cooling fan relay should be retested to determine if it is still in a useable condition.