Rebuilding/cleaning AC control module

[Drewhenry]

My AC fan switch and or AC motor finally crapped out on me on my way to a duck hunt this morning.

I got 2 Whistlers, 1 Widgeon, and 3 Blue-Winged Teal. Wasn't about to let a bad AC chingle my hunt.

Got home and pulled the appropriate panels and removed the control module. Took it apart. Very easy.

There is some kind of grease-conductive I assume-between the contacts in the switch.
Can I simply clean this stuff out and dab a bit more conductive grease in there?

The 3 little light bulbs that illuminate the panel are burned out, but are very simple to remove as well-twist and the units fall out.
Are these light bulbs available anywhere?

I ordered new fan w/squirrel from Ebay and a control module that will be here in a week.
I believe it is the switch more than the motor, but I could be wrong.

Thanks in advance for any/all advice & information.

Andy B

 

[Motorhead]

The grease is the opposite of what you are calling it. It is a dielectric non conductive grease that is put there to help preserve clean contacts and to repel moisture. I would check the contacts carefully and make sure they are clean and make good contact. You can buy the dielectric grease at most auto parts stores and at NAPA auto parts. Are you sure that the switch is at fault? Depending on use and how much dust you drive in with the HVAC working, the motor brushes might be worn enough to not contact the armature.
I'm not a Duck hunter but it sounds like you did well!

 

[Prairie Dog]

​The known issue is cold/cracked solder joints. Nothing is going to fix cold solder joints other than re-flowing them.

 

[Motorhead]

Fixed many electronic items by the same way ^^.

 

[User113]

You can check out the fan motor by just "jumpering" power to it, sure beats pulling the fan out only to find it was not the problem. However, I would suspect the fan speed resistor first. In any event, all these things are easy to check out before you replace them.

As for the solder joints, that is often a weak spot because of the way things are "wave soldered." You may be able to fix the solder joints all at once in your oven, but if there are not that many solder joints, a hand-held soldering iron will be able to fix them if that is in fact the problem.

 

[Motorhead]

How do you get it hot enough to melt the solder in the OVEN without cooking all of the components and any plastic? The way I have seen production of soldering components on a circuit board was to pass them over a flowing melted solder pool.

 

[Drewhenry]

However, I would suspect the fan speed resistor first.

Where is the fan speed resistor located? How do I get to it? How do I check it?

Andy B

 

[Motorhead]

I'd have to look at a manual but the fan speed resistor is usually mounted in the HVAC air box with the resistor coils facing inside the air flow to keep them cool. You can test them with a Volt/Ohm meter but they are usually big enough and open coils of resistance wire where you would probably see a break in the wire. I would check for the location of the resistor either behind the glove box or above the passenger foot well.

 

[rashwor]

On my '05, the resistor is located in the housing next to the fan (in that area). When mine was acting up a couple of years ago, I tried everything like you are and it ended up being the fan motor.

 

[Motorhead]

It is usually the fan motor brushes that cause the motor to quit. The motor also gets cooling air from the HVAC air flow. Any dust through the system can hasten the brushes wear faster.

 

[User113]

How do you get it hot enough to melt the solder in the OVEN without cooking all of the components and any plastic? The way I have seen production of soldering components on a circuit board was to pass them over a flowing melted solder pool.

https://en.wikipedia.org/wiki/Reflow_soldering

https://www.youtube.com/watch?v=Vz_AGCXrTy8

https://www.youtube.com/watch?v=gvvQ10hlgb0

I can't say I've tried it, but the theory is sound.

 

[User113]

It is usually the fan motor brushes that cause the motor to quit. The motor also gets cooling air from the HVAC air flow. Any dust through the system can hasten the brushes wear faster.

I agree, but it is so easy to check the resistor that it would be silly not to before tearing into the blower motor.

DIAGNOSIS AND TESTING - BLOWER MOTOR
RESISTOR BLOCK

WARNING: ON VEHICLES EQUIPPED WITH AIRBAGS,
DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISOLATE
THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYSTEM
CAPACITOR TO DISCHARGE BEFORE PERFORMING
FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRECAUTIONS
COULD RESULT IN AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.

For circuit descriptions and diagrams, refer to the
appropriate wiring information. The wiring information
includes wiring diagrams, proper wire and connector
repair procedures, further details on wire
harness routing and retention, as well as pin-out and
location views for the various wire harness connectors,
splices and grounds.

(1) Disconnect and isolate the negative battery
cable.

(2) Disconnect the wire harness connector from the
blower motor resistor block.

(3) Check for continuity between each of the
blower motor switch input terminals of the resistor
and the resistor output terminal. In each case there
should be continuity. If OK, repair the wire harness
circuits between the blower motor switch and blower
motor resistor or blower motor as required. If not
OK, replace the faulty blower motor resistor block.

 

[Drewhenry]

Hadn't thought about the airbags. Thanks. The reason I suspected the motor was it has been on the fritz for a while. Bumping the motor housing from the outside (with a golf putter while driving) would make the fan come on sometimes. Lately the fan RPMs have been less and less and finally nothing. New motor should be here today-9th. New Control panel arrived on the 8th.

Andy B

 

[Prairie Dog]

It takes about 450 degrees to reflow solder. Components are rated to take that temp for only a short time (seconds).
During the wave solder process the heat is supplied in a controlled manner so as not to exceed this spec.
cooking it in an oven that is hot enough to melt solder is more than likely going to destroy it.

 

[Motorhead]

What Prairie Dog said is what I was thinking. I guess if you have a circuit board not working, what do you have to lose?

 

[Drewhenry]

New Motor fixed the MAJOR problem. After installing the NOS control panel, still no illumination. Indicator light for compressor doesn't work, indicator light for heated mirrors blinks steadily. If I can get the illumination to function in my original control panel that would be awesome. I am not sure I understand the "known" problem. Are you saying the bulbs are still good but the solder joints have failed? The bulbs seem to be firmly soldered into their respective discs. I thought they were just burned out.

Andy B

 

[User113]

It takes about 450 degrees to reflow solder. Components are rated to take that temp for only a short time (seconds).
During the wave solder process the heat is supplied in a controlled manner so as not to exceed this spec.
cooking it in an oven that is hot enough to melt solder is more than likely going to destroy it.

Most electronics solders will melt between 360° and 370° (see https://en.wikipedia.org/wiki/Solder (it's on the Internet, so it's gotta be true )). Through-hole solder boards, where the components are on one side of the board and the leads are inserted through holes to be soldered from the other side of the board are often soldered using wave soldering techniques. However, more modern circuit boards are made with the components and the leads on the same side of the board (or film, or whatever). These "surface mount" components are soldered commercially in "reflow ovens." They start with bumps of solder on the board's pads, the components are placed on top of the solder bumps, and the board is heated in the reflow oven. As the name implies, the solder melts for a second time and "reflows." connecting the leads to the pads. While the ovens might heat to 450°, the components won't get that hot in the short amount of time it takes to reflow the solder.

 

[Prairie Dog]

Most electronics solders will melt between 360° and 370° (see https://en.wikipedia.org/wiki/Solder (it's on the Internet, so it's gotta be true )). Through-hole solder boards, where the components are on one side of the board and the leads are inserted through holes to be soldered from the other side of the board are often soldered using wave soldering techniques. However, more modern circuit boards are made with the components and the leads on the same side of the board (or film, or whatever). These "surface mount" components are soldered commercially in "reflow ovens." They start with bumps of solder on the board's pads, the components are placed on top of the solder bumps, and the board is heated in the reflow oven. As the name implies, the solder melts for a second time and "reflows." connecting the leads to the pads. While the ovens might heat to 450°, the components won't get that hot in the short amount of time it takes to reflow the solder.

Yes, I'm very familiar with CB construction and Wave solder flow. Worked in industry for many years.
The part you missed was the "reflow". To reflow the temps are set to what I mentioned (roughly). Simple first time hand soldering takes less heat. The second time takes more.
Remember, we're not trying to melt the solder with the heat source. We're trying to get the CB and components hot enough to melt it and that takes more heat transfer.