Variable Blower Control Module Repair

[ShelbyDoug]

Is anyone repairing these things? I have a few that I burnt out. New ones are over $200 each.

 

[hawkeye18]

The big heat-sunk transistor is usually what goes out on them. Either that or the relay goes bad. I haven't figured out specifically what transistor it is, and I can't find a suitable replacement. I haven't tried all that hard, however.

 

[sperold]

When they "go", do they stop working, or work only on the high speed?

 

[hawkeye18]

If the relay shorts out, it'll generally only work on high speed. If the transistor shorts out, it'll pop the fuse as soon as you energize the system.

 

[sperold]

It would be nice to be able to fix these things, and it sounds like the relay is the problem. Does one from any other car work?

 

[jelloslug]

It would be nice to be able to fix these things, and it sounds like the relay is the problem. Does one from any other car work?

The only other car with the 4 wire BCM is the 88-94 Lincoln Continental.

 

[ShelbyDoug]

The only other car with the 4 wire BCM is the 88-94 Lincoln Continental.

The SHO essentially has a Lincoln a/c system in it. They have the same problem with the blower module since it is the same unit.

The used ones are probably 50% used up already and are at a premium in the wrecking yards since the "limo" guys all want them.

Awhile a go there was someone on the Forum that was interested in repairing them. That was why I was inquiring about them.

So far I haven't found anyone, and electronics repairs are not my thing.

 

[Shovert]

I thought. Most electronic parts have a number on them. If big enough to print on. I haven't seen what you talking about. Someone post part etc. Then you make take to local Radio Shack to source part and talk to them. They usually knows someone that will do small jobs like them. Just thinking outloud. Maurice

 

[jelloslug]

The SHO essentially has a Lincoln a/c system in it. They have the same problem with the blower module since it is the same unit.

The used ones are probably 50% used up already and are at a premium in the wrecking yards since the "limo" guys all want them.

Awhile a go there was someone on the Forum that was interested in repairing them. That was why I was inquiring about them.

So far I haven't found anyone, and electronics repairs are not my thing.

The Town Car uses a different module. Here, there are no "limo" guys so the modules are a dime a dozen.

 

[ShelbyDoug]

E9DH-19E747-RB is a broken one that I have here in front of me now. I bought it used and it is marked, '90 Cont.
To me they are the same parts.
Sorry that there are no limo guys in SC Jello. I guess there are still places in the country that think electricity is a wonderful new discovery.
You are missing so much. Some of them even speak English and don't give you the finger?

 

[jelloslug]

E9DH-19E747-RB is a broken one that I have here in front of me now. I bought it used and it is marked, '90 Cont.
To me they are the same parts.
Sorry that there are no limo guys in SC Jello. I guess there are still places in the country that think electricity is a wonderful new discovery.
You are missing so much. Some of them even speak English and don't give you the finger?

We all have cars here, we don't need some ******* from Brooklyn to drive us around in a beat down Town Car with 400,000 miles on it.

 

[sperold]

Whoa, this took a turn for the worst.
I was hoping this would be one of those threads where I would learn something.
Lets get along, I am tired of having a fan that works only on high.

 

[jelloslug]

Whoa, this took a turn for the worst.
I was hoping this would be one of those threads where I would learn something.
Lets get along, I am tired of having a fan that works only on high.

I'm sure that some place like Digi-key or Mouser would have the discrete components that are on the board. The device itself is rather simple.

 

[sperold]

The sad thing is, i have never heard of those places. I will take a look.
Thanks for everything so far.

 

[hawkeye18]

I was planning on trying to repair them a [long] while back, but ran out of time and resources. If you find a replacement, and want to send the original broken one to me, I can take a whack at trying to repair it. The relay pack really shouldn't be hard to find a replacement part for - a relay's a relay.

That transistor could be a problem. Others have tried to find a replacement part - or a tech sheet on the original, and have had no luck.

It is pretty obviously a current limiting MOSFET of some sort - but of what sort? It could be very difficult to determine the characteristics of it, especially if it's broken.

 

[93rev2sev]

Seems like the logical solution is to redesign the system to have a manual BDA.

 

[jelloslug]

Seems like the logical solution is to redesign the system to have a manual BDA.

We are talking about the blower control module, not the blend door actuator.

 

[hawkeye18]

Seems like the logical solution is to redesign the system to have a manual BDA.

We are talking about the blower control module, not the blend door actuator.

This is true, we are talking about the BCM, but it's still a valid question - you could absolutely turn it into a manual system, except that the fan speed input to it is not stepped like it is in a manual HVAC system (you know - 0, 1, 2, 3), it's a linear sloping voltage that biases the current limiting MOSFET.

In manual HVAC systems, you will have a Blower Motor Resistor instead of the BC Module - and that's just basically three or four big resistors that act as discrete current limiters. If only it were that simple.

The best part is, it honestly would not be that difficult to design a circuit using modern parts that would accomplish the same thing the BCM does for pretty darn cheap. I could probably do it inside a week, and that includes breadboarding, etc. The problem is, it'd be useless in an actual vehicle as a) it probably wouldn't last nearly as long as the originals did, and b) packaging would be a problem to say the least.

If only we could find the modern successor to that 6500FG...

 

[jelloslug]

This is true, we are talking about the BCM, but it's still a valid question - you could absolutely turn it into a manual system, except that the fan speed input to it is not stepped like it is in a manual HVAC system (you know - 0, 1, 2, 3), it's a linear sloping voltage that biases the current limiting MOSFET.

In manual HVAC systems, you will have a Blower Motor Resistor instead of the BC Module - and that's just basically three or four big resistors that act as discrete current limiters. If only it were that simple.

The best part is, it honestly would not be that difficult to design a circuit using modern parts that would accomplish the same thing the BCM does for pretty darn cheap. I could probably do it inside a week, and that includes breadboarding, etc. The problem is, it'd be useless in an actual vehicle as a) it probably wouldn't last nearly as long as the originals did, and b) packaging would be a problem to say the least.

If only we could find the modern successor to that 6500FG...

Frankly, the easiest solution is to just switch the EATC head and the BCM over to the five wire BCM that is used in every other Ford product. Those parts are a dime a dozen.

 

[Shovert]

Now that is a good thought. I have consider that eatc for the Mustang. Seem like we can never decide warm or cold. Now I have the printout from p71 interceptor on swap in crownvic. Seems like that site is dead or not up. [glad I printed it] Found the wiring diagram for the 5 wire one used on them if that helps. Maurice
http://media.photobucket.com/image/crownvic eatc wiring diagram/rtg143/Eatc1.jpg