94 850 with ECC- no fan

  • Thread starter Thread starter JDG
  • Start date Start date
J

JDG

Can anyone provide resistances for the blower motor power stage so I can
trouble shoot it? My fan stopped,no blinking lights on ECC unit,and I
think it could the power stage(actually the resistors for the blower
motor speeds). Also, where is the relay for the blower motor located? My
Haynes manual doesn't help much in this area. AC cycles on with AC
on/off and cycles on with defrost setting. Just no fan at any speed setting.
 
JDG said:
Can anyone provide resistances for the blower motor power stage so I can
trouble shoot it? My fan stopped,no blinking lights on ECC unit,and I
think it could the power stage(actually the resistors for the blower
motor speeds). Also, where is the relay for the blower motor located? My
Haynes manual doesn't help much in this area. AC cycles on with AC
on/off and cycles on with defrost setting. Just no fan at any speed setting.
Click to expand...



If your unit has continuously-variable blower speed, the "power
stage" and is a heat sink for one or more transistors that supply the
current to the fan motor. The factory manual lsits either DTC codes
(connector B1) or substitution for troubleshooting this part.

The schematic also shows a manual system, where there there are
several fixed blower speeds. This uses a resistor pack
Pin 4 (green wire) is the common, and three resistors go from there to
pins 1,2,3 (black, black/white, brown)

They don't show the resistor values, but if one was bad, it should
still work on some speeds.
 
Doug said:
If your unit has continuously-variable blower speed, the "power
stage" and is a heat sink for one or more transistors that supply the
current to the fan motor. The factory manual lsits either DTC codes
(connector B1) or substitution for troubleshooting this part.

The schematic also shows a manual system, where there there are
several fixed blower speeds. This uses a resistor pack
Pin 4 (green wire) is the common, and three resistors go from there to
pins 1,2,3 (black, black/white, brown)

They don't show the resistor values, but if one was bad, it should
still work on some speeds.
Click to expand...

The problem with no fan on any speed was the resistor for the blower
motor. I bought a used one and changed it out. None of the codes I
pulled on my 94 850 said "bad resisor". There was tons of crap about
shorted to ground sensors- about 15 different codes. I think the system
just is not set up to diagnose a bad resistor for the blower motor.
Thanks- JDG
 
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