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Rear View Mirror display flaking out

71GMC_3/4T

By 71GMC_3/4T
in Ask A GM Technician

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71GMC_3/4T Enthusiast

71GMC_3/4T

Posted
Posted

GM-Tech,

My Compass/temperature display flaked out the other day.

It has OnStar, but it's not activated.

Both green LEDs (on/off and Onstar) would go out along with the display, and a second later the LEDs would come on and the temp/compass display would light up all the segments and then show the temperature and direction for a couple of seconds, then it would blank out and do it all over again, and again...

Since both LEDs and the display all went out at once, I'm suspecting a bad ground somewhere.

Does the mirror assy get power from two different locations for temp/compass and Onstar?

Is there a ground above the headliner that might be bad, or a ground somewhere else that might be loose? I think wiggling the wires above the mirror may have helped it, but it was so intermittant I really couldn't tell.

The problem happened Thursday night, and hasn't come back since. :chevy:

Any insight you could provide would be great! :jester:

Thanks!

GM-Tech Senior Enthusiast

GM-Tech

Posted
Posted

Everything shares a ground, but what turns on the various things is different, so I suppose it could be a ground. There's a splice pack right at the bottom of the left pillar molding that contains a number of grounds, so I wouldn't think the problem would be there, otherwise you'd lose more than just the mirror. More likely, something right at the mirror connector, but that's a guess.

71GMC_3/4T Enthusiast

71GMC_3/4T

Posted
  • Author
Posted

Thank you sir!

 

I'll go pull the mirror assy off the windshield and take a look inside.

 

What's up w/ GM's solder quality? Did they recently make a switch to lead-free solder or something? I've already had to reflow the solder on my 4x4 selector switch after it flaked out and went blank. By the way, that problem hasn't come back since on the 4x4 switch.

 

I was looking for something to do this weekend - crappy weather sux bad...

 

I'll let you know if I find or f-up anything!

GM-Tech Senior Enthusiast

GM-Tech

Posted
Posted
Did they recently make a switch to lead-free solder or something?

 

Lead-free solder :jester: That's a good one. I honestly don't know what the problem is. I guess when you get into mass producing millions of parts, things can happen.

71GMC_3/4T Enthusiast

71GMC_3/4T

Posted
  • Author
Posted
Lead-free solder  :lol:  That's a good one. 

 

 

 

 

Actually, it's for real. :chevy:

 

The world is switching to lead-free solder for electronic assemblies. It's starting in Europe next year I think. I noticed the mirror had an IEC number on it, and that's where it all starts, with IEC... I think it's all :jester: , but there probably *is* a lot of lead being dumped in the landfills.

 

Anyways, I pulled the mirror off and took it apart. Man, there's a lot of circuitry in there! And a lot that isn't stuffed, like LEDs that would shine through the center bottom of the mirror. What are they for? Radar detector??

 

The main connector had 3 pins tied to the ground plane. I reflowed the solder on all the pins to that connector. I have to assume one ground pin is the main return, and the other two grounds go on to other modules.

 

You're right, they have different sources which I confirmed tonight. When the key is in ACC, you have OnStar LED only. IGN gets the compass/temp and AutoDimmer mirror, and still ONstar. So for all of the indicators to flash on/off at once, it would almost have to be an intermittant ground.

 

Out in the front of the mirror is a box with two little things that look like relays. Are these the compass sensors? They are mounted 90 degrees from each other.

GM-Tech Senior Enthusiast

GM-Tech

Posted
Posted
Out in the front of the mirror is a box with two little things that look like relays.  Are these the compass sensors?  They are mounted 90 degrees from each other.

 

Dunno. Never really looked that closely at one. Doesn't work? Got power and ground? Replace it. That's as much as we get into it. :jester:

mjwencl Enthusiast

mjwencl

Posted
Posted
GM-Tech,

My Compass/temperature display flaked out the other day.

It has OnStar, but it's not activated.

Both green LEDs (on/off and Onstar) would go out along with the display, and a second later the LEDs would come on and the temp/compass display would light up all the segments and then show the temperature and direction for a couple of seconds, then it would blank out and do it all over again, and again...

Since both LEDs and the display all went out at once, I'm suspecting a bad ground somewhere. 

Does the mirror assy get power from two different locations for temp/compass and Onstar?

Is there a ground above the headliner that might be bad, or a ground somewhere else that might be loose?  I think wiggling the wires above the mirror may have helped it, but it was so intermittant I really couldn't tell.

The problem happened Thursday night, and hasn't come back since.  :confused:

Any insight you could provide would be great!  :tear:

Thanks!

 

 

 

 

Mine has done this several times over the winter months and once during a cold rain. Hmmm... Cold / Moisture related bad ground? I haven't had mine looked at yet by the dealer.

71GMC_3/4T Enthusiast

71GMC_3/4T

Posted
  • Author
Posted

Mine did it last week when it was sunny and warm in the morning, and by mid-afternoon we were getting hammered with snow. Ahhhh, Colorado! Gotta love the weather here...

 

I think it was due to the rapid temperature change. A quick change like that will uncover all sorts of weird intermittants. I think I had something similar with the 4x4 selector switch too. It sat where the sunlight warmed up the dash on that side, then when the sun went down and I went to go home, it flaked out.

 

I've reflowed the solder on both the 4x4 selector and mirror assy. I haven't had any issues with the 4x4 module since, and it's too soon to say whether or not the mirror is fixed or not. Yeah, I coulda taken it into the dealer, where I would have gotten the runaround since it would have probably worked just fine at that time. And if they had found the problem, it would have been a full module replacement, likely just as bad as the old one, waiting to fail at a later date out of warranty. This way, I know how well it's soldered. I used some really nice silver bearing electronic solder when I redid them.

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