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Old 09-10-2008, 07:25 PM   #1
bozr
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Blank display in the Dual Zone Climate Control Module

This a continuation of my original post here.
http://www.automotiveforums.com/vbul...d.php?t=916787
I felt it needed it’s own thread as the original problem had diverged and the title wouldn’t be appropriate for someone searching for an answer. I would have liked to make it short and sweet but too little information could be worse than the original problem.

Otherwise known as the HVAC Control Assembly, the digital display can dim, flicker or go out completely.
Broken solder joints on components in the displays power circuit cause the problem.



This is the unit disassembled.




The problem with the board is with the surface mount resistors here circled in red.



A closer look reveals cracks in the solder joints on one side of all 8 resistors.



Removing the HVAC Control Assembly from the dash is simple.
Remove the two screws from the bottom of the trim panel below the ashtray.
Open the glove compartment and grasp the side of the trim panel to pull it out of the clips that hold the upper section.
Remove the two screws that hold the unit in the dash.
Disconnect the harness.

Dissipate any static electricity you may have accumulated by touching a metal object before you handle the circuit board.
There are 4 screw holding the case together and 4 screws holding the board (see picture above).
Keep the faceplate pointed down so the buttons don’t fall out.
Disconnect the harness from the connector on the board, don’t worry, it only goes in one way.

A good tutorial on soldering surface mount components can be found here;
http://curiousinventor.com/guides/Su..._Soldering/101
Following the techniques in the video will make this repair a breeze.

With all the money I was going to save I bought a digital soldering station. Seriously though, I could use it for other projects but I needed to know what temperature would work with the components. 680F was one of the highest preset temperatures and worked well, quickly melting the joint without imparting a lot of heat into the component. Some of the inexpensive higher watt pencil irons from Radio Shack should work fine if you get the smaller tip.
Since I had never soldered SMC’s I practiced on a circuit board out of a dead DVD drive.
The main difference is that you won’t be adding solder at the component like you do when you solder wire, instead, you’ll just add a small amount of solder to the tip of the iron.

To start, flux the joints first then heat up the part and drag the tip across the edge of the joint. The joint will automatically take or leave solder from the tip as it needs it. I used paste flux and applied it to the joints with a toothpick.
At 680F the solder starts melting in about 1.5 seconds. If it takes longer than 5 seconds you’ll need a hotter iron. Leaving the iron on the part for too long can damage it. If the joint doesn’t look good go on to the next one and let that one cool down before attempting it again.
Solder the broken side first so the part doesn’t come loose from the board. You can use a toothpick to hold light pressure on the component while you solder.

Things you’ll need;
Soldering iron
Can of tinner/cleaner
.032 Rosin Core Solder
Can of paste flux
Jewelers Loupe

You’ll need the jewelers loupe because you’ll be doing your soldering through it. Besides that, they’re good for reading plugs and credit card applications. About $5 at Sears Hardware.

Here’s the finished product.
Good luck






Last edited by bozr; 09-13-2008 at 07:08 PM.
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