- Joined
- Jul 10, 2009
- Messages
- 331
- Reaction score
- 4
- Points
- 18
- Location
- Harrisburg PA
- Vehicle Year
- 97
- Make / Model
- Ford
- Engine Size
- 4.0 OHV
- Transmission
- Automatic
Ok my second vehicle is a 2004 Chevrolet Impala (picked it up for 2500 a few years back) so I have an inoperative rear window defogger. Going thru and doing testing According to numbers I have it should be working but it won't. My Brother bough the car new in 2004 and said it was some time in 2005 is when the defogger stopped working and he just never cared as to why and went on with it not working.
There is a 4 pin relay and circuit breaker in the passanger side fuse box that control the defogger.
Pin out for the relay:
N3: Load Management from BCM / Pin 86 on relay 14.35 volts with engine running /.56v engine off
N2: Relay out to circuit breaker / Pin 87 on relay no voltage. Wire is good from Box to the rear window no resistance.
L3: Hot at all times 14.35 volts engine running / Battery voltage with engine off
L2: Ground signal from HVAC control unit Open circuit with switch off / completes ground ciruit when switch is pushed and also tested usign it as a ground ot test voltages on N3 and L3.
Looking at the numbers the defogger should work and points to a bad relay, I swapped the relay with 2 different relays from the cooling fans and it acts the same way but the fans work with the relays as they are supposed to. I took the cover off of one of the relays and if I manually push the contact closed it will energize the rear defooger as long as I hold it.
Does anyone have any insight on what I am over looking on this set up.
Ohh I have also tried 2 different HVAC control unit both yeilding the same results.
There is a 4 pin relay and circuit breaker in the passanger side fuse box that control the defogger.
Pin out for the relay:
N3: Load Management from BCM / Pin 86 on relay 14.35 volts with engine running /.56v engine off
N2: Relay out to circuit breaker / Pin 87 on relay no voltage. Wire is good from Box to the rear window no resistance.
L3: Hot at all times 14.35 volts engine running / Battery voltage with engine off
L2: Ground signal from HVAC control unit Open circuit with switch off / completes ground ciruit when switch is pushed and also tested usign it as a ground ot test voltages on N3 and L3.
Looking at the numbers the defogger should work and points to a bad relay, I swapped the relay with 2 different relays from the cooling fans and it acts the same way but the fans work with the relays as they are supposed to. I took the cover off of one of the relays and if I manually push the contact closed it will energize the rear defooger as long as I hold it.
Does anyone have any insight on what I am over looking on this set up.
Ohh I have also tried 2 different HVAC control unit both yeilding the same results.