AutoXSHO
SHO Member
Guys,
Here are a few pictures and a short writeup on some issues I've found with the EATC blower control modules. Symptoms of this module failing are:
* Blower speed cannot be controlled with the EATC
* Erratic or intermittent blower operation
* Blower runs when EATC head unit indicates "OFF"
The failure mechanisms of this module are fairly widespread it seems but they all stem from one cause: corrosion. Ford saw fit to cool the module's electronics by putting it inside the heating duct. The humidity wreaks havoc on the electronics. Here are some pictures.
Here is what you are looking for. It's behind the glovebox near the ventilation ducts.
This is pretty typical for how the BCMs look when they come out. Notice all the dirt around the relay (********* box) and the resistors. The red stuff is circuitboard RTV, at least Ford tried to keep them dry. The big gray part is a heat sink for the output power transistor.
This next image shows the backside. All the little rectangles are surface mount resistors, diodes, and capacitors. This board is in pretty good shape. The arrows point to a rotted trace on the left and a rotted resistor on the right. The trace will have to be repaired by hand etch or by laying some wire down. The resistor can be replaced.
5% Surface mount resistors are coded as follows: The first two numbers are the first two digits of the resistor. The last digit is the multiplier. So on the resistor we see:
102 would be 10 times 10 to the second = 10 * 100 = 1000. This is a 1k resistor.
682 is a 6800 or 6.8k resistor and so on.
The next picture shows the backside of the board all cleaned up with the traces repaired and the bad resistor replaced. It's hard to see, because the flash of the digital camera reflects off the copper and it's very hard to focus on the small stuff. I'll try to get a better one.
And here is one of the front side. This particular board's problem was a rhythmic clicking noise. Throughhole capacitor C5 (10uF, 50V) had a rotted lead and was separated from the board. I removed the relay so you can see the position of this capacitor. I replaced it with an identical electrolytic cap (remember polarity!!).
The arrows point to the new capacitor (installed) and the legless wonder on the lab table.
The relay on this board is also junk. It has a loose piece inside it, probably due to moisture and many years of use. I'm having an Omron rep cross reference a relay for me since this SPST relay's part number is not listed. Probably it was a special OEM part number for Ford. Yes, I tried looking for the Ford part number E9DF-14A640-AA that is printed on the relay: no luck.
In the meantime I'm adapting a standard SPST 30A relay to this board and it will be sent back to the owner after a thick coating of circuitboard RTV is applied to it.
Hope this helps anyone looking to repair their malfunctioning blower control module. I know the pictures aren't the greatest, but you get the idea. I have a list of all the SMT parts used on this board so if you need to replace components and can't read your rotted resistors let me know.
John V
<small>[ March 19, 2002, 01:14 PM: Message edited by: AutoXSHO ]</small>
Here are a few pictures and a short writeup on some issues I've found with the EATC blower control modules. Symptoms of this module failing are:
* Blower speed cannot be controlled with the EATC
* Erratic or intermittent blower operation
* Blower runs when EATC head unit indicates "OFF"
The failure mechanisms of this module are fairly widespread it seems but they all stem from one cause: corrosion. Ford saw fit to cool the module's electronics by putting it inside the heating duct. The humidity wreaks havoc on the electronics. Here are some pictures.
Here is what you are looking for. It's behind the glovebox near the ventilation ducts.
This is pretty typical for how the BCMs look when they come out. Notice all the dirt around the relay (********* box) and the resistors. The red stuff is circuitboard RTV, at least Ford tried to keep them dry. The big gray part is a heat sink for the output power transistor.
This next image shows the backside. All the little rectangles are surface mount resistors, diodes, and capacitors. This board is in pretty good shape. The arrows point to a rotted trace on the left and a rotted resistor on the right. The trace will have to be repaired by hand etch or by laying some wire down. The resistor can be replaced.
5% Surface mount resistors are coded as follows: The first two numbers are the first two digits of the resistor. The last digit is the multiplier. So on the resistor we see:
102 would be 10 times 10 to the second = 10 * 100 = 1000. This is a 1k resistor.
682 is a 6800 or 6.8k resistor and so on.
The next picture shows the backside of the board all cleaned up with the traces repaired and the bad resistor replaced. It's hard to see, because the flash of the digital camera reflects off the copper and it's very hard to focus on the small stuff. I'll try to get a better one.
And here is one of the front side. This particular board's problem was a rhythmic clicking noise. Throughhole capacitor C5 (10uF, 50V) had a rotted lead and was separated from the board. I removed the relay so you can see the position of this capacitor. I replaced it with an identical electrolytic cap (remember polarity!!).
The arrows point to the new capacitor (installed) and the legless wonder on the lab table.
The relay on this board is also junk. It has a loose piece inside it, probably due to moisture and many years of use. I'm having an Omron rep cross reference a relay for me since this SPST relay's part number is not listed. Probably it was a special OEM part number for Ford. Yes, I tried looking for the Ford part number E9DF-14A640-AA that is printed on the relay: no luck.
In the meantime I'm adapting a standard SPST 30A relay to this board and it will be sent back to the owner after a thick coating of circuitboard RTV is applied to it.
Hope this helps anyone looking to repair their malfunctioning blower control module. I know the pictures aren't the greatest, but you get the idea. I have a list of all the SMT parts used on this board so if you need to replace components and can't read your rotted resistors let me know.
John V
<small>[ March 19, 2002, 01:14 PM: Message edited by: AutoXSHO ]</small>
