Auto-Climate Control help please
Hotshot
Joined: Jan 2004
Posts: 19,765
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From: St Louis
ericatp01,
Full battery voltage is applied to one terminal of the blower via the blower relay. Speed is controlled by varying the effective resistance of the return side of the circuit electronically by the blower speed controller (BSC) module under the control of the EATC module.
If you have no voltage on the BSC side of the blower but have the battery voltage on the relay side, the motor is bad, probably due to failed brushes.
Full battery voltage is applied to one terminal of the blower via the blower relay. Speed is controlled by varying the effective resistance of the return side of the circuit electronically by the blower speed controller (BSC) module under the control of the EATC module.
If you have no voltage on the BSC side of the blower but have the battery voltage on the relay side, the motor is bad, probably due to failed brushes.
New User
Joined: Aug 2010
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Thank you very much for your reply.
I have NO voltage shown at the speed control box. There is a ground wire, a red wire (small) and a brown wire (I believe it is brown) that is the same size as the ground wire. I show no voltage at these points.
Also I verified I have no voltage to either side of the blower motor connector. That would seem obvious since I had no voltage to the speed control box, but I checked it again anyway.
Leaving the relay under the dash in the flasher housing, I see voltage and the relay seems to be working normally.
Im normally very good at electrical trouble shooting, but Im kind of shooting blind here.
Thank again for the help. It is much appreciated.
Eric
I have NO voltage shown at the speed control box. There is a ground wire, a red wire (small) and a brown wire (I believe it is brown) that is the same size as the ground wire. I show no voltage at these points.
Also I verified I have no voltage to either side of the blower motor connector. That would seem obvious since I had no voltage to the speed control box, but I checked it again anyway.
Leaving the relay under the dash in the flasher housing, I see voltage and the relay seems to be working normally.
Im normally very good at electrical trouble shooting, but Im kind of shooting blind here.
Thank again for the help. It is much appreciated.
Eric
Hotshot
Joined: Jan 2004
Posts: 19,765
Likes: 1,082
From: St Louis
Grab schematic: 2000 Expedition EATC BSC.pdf
It's easier if you can see how it's supposed to work. Check fuse F105 under hood and fuses F2 and F22 under the dash while you're at it.
It's easier if you can see how it's supposed to work. Check fuse F105 under hood and fuses F2 and F22 under the dash while you're at it.
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Joined: Aug 2010
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Ok, again thanks for the diagram. Here is the deal. The relay in the Blower / Flasher block is not closing. When power is turned on I get power to connector 86 on the relay, but there is no ground made on connector 85 though the EATC.
Based on this diagram it looks like the EATC has a failure that is not allowing it to complete the ground circuit for the relay to close. Everything else works normally on it.
I removed the cover on a replacement relay and verified it was not closing. I then mechanically closed the relay with my finger and the blower powers up and works normally.
It seems really odd to me how just the one circuit in the EATC control module could cause this but I don't see anything else obvious.
Any other ideas.
Thank you,
Eric
Based on this diagram it looks like the EATC has a failure that is not allowing it to complete the ground circuit for the relay to close. Everything else works normally on it.
I removed the cover on a replacement relay and verified it was not closing. I then mechanically closed the relay with my finger and the blower powers up and works normally.
It seems really odd to me how just the one circuit in the EATC control module could cause this but I don't see anything else obvious.
Any other ideas.
Thank you,
Eric
Hotshot
Joined: Jan 2004
Posts: 19,765
Likes: 1,082
From: St Louis
I'd suspect a a failed output driver chip or transistor if there is continuity between the output pin of the EATC and the relay coil.
Based on the cost of a replacement EATC, I'd be hot-wiring that sucker so the relay energizes whenever the ignition is in RUN or something similar
Based on the cost of a replacement EATC, I'd be hot-wiring that sucker so the relay energizes whenever the ignition is in RUN or something similar
Thread Starter
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Tuned
Joined: Aug 2002
Posts: 263
Likes: 0
From: USA
I'm back to working on mine again 
The new blower motor I put in from AutoZone only lasted a couple months! Possible bad part, or maybe there was too much amperage being drawn. It's lifetime warrantied, but that thing was a PITA to put in!
Anyway, does anyone know what acceptable amperage is for that motor to be pulling? I found the motor's bad by plugging in the original which still works, but is somewhat harder to turn, and possibly making it draw too much amperage. At any rate I just wanted to check there's not too many amps being drawn after I install the next blower fan.
The new blower motor I put in from AutoZone only lasted a couple months! Possible bad part, or maybe there was too much amperage being drawn. It's lifetime warrantied, but that thing was a PITA to put in!Anyway, does anyone know what acceptable amperage is for that motor to be pulling? I found the motor's bad by plugging in the original which still works, but is somewhat harder to turn, and possibly making it draw too much amperage. At any rate I just wanted to check there's not too many amps being drawn after I install the next blower fan.
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