Rear hvac module discontinued. Can mine be repaired?

For now I manually set the actuator and unplugged it, all heat all the time. Once I get a replacement maybe I'll crack open the defective one and see what makes it tick (or fail to tick).

On my '04 Auto HVAC there are 6 calibrations (firmware) for the front and rear units, 3 each. All of the updated calibrations for these have been issued long ago, and a good scanner will tell you what calibrations exist in yours. Then you can check with your dealer or someone who can program modules to see if yours need to be updated.

Here are my calibrations (not part numbers) when I read them with my Tech 2, when I had it.

Fless said:

On my '04 Auto HVAC there are 6 calibrations (firmware) for the front and rear units, 3 each. All of the updated calibrations for these have been issued long ago, and a good scanner will tell you what calibrations exist in yours. Then you can check with your dealer or someone who can program modules to see if yours need to be updated.

Here are my calibrations (not part numbers) when I read them with my Tech 2, when I had it.

View attachment 443208

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I've come across a few mentions of calibration, lots that seem to say the mods are plug n play. Funny how a mass produced part like this can remain such a confounding variable after all this time.

Stickle said:

I've come across a few mentions of calibration, lots that seem to say the mods are plug n play. Funny how a mass produced part like this can remain such a confounding variable after all this time.

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The Dorman (and likely other aftermarket brand) modules will probably have the latest calibrations; they should be marketed as PnP if they are. GM hasn't issued new calibrations for these for years, so they're static at this point, and if the aftermarket mfr. uses them it'll be the latest. If you pull a module from the junkyard it may or may not have been updated.

76Nick said:

Hey guys, so my hoe has the typical no rear heat issue due to the rear hvac module being bad. Dorman used to make a replacement however that seems to no longer be available. My question is, does anyone know how to repair my current one since this is a common issue? I figured maybe someone has done it or there is a way to do it, sort of like the lighting on the gauge cluster being able to be repaired by resoldering a connection in it. Thank you!

Nick

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Had this same problem with my ‘05. Started 6 months “after” checking and replacing all blend door actuators (front and rear). After watching a YouTube video on testing this modulator, I actually called Dorman and got a similar answer.

Problem is with junk yards, this piece not that plentiful - “in good working order”. I bought 2 used (from junk yards) on separate occasions, only to see them fail within a few months.

So I decided to go a seasonal change over - in the spring I would set the blend door actuator back there to blow cold. In the fall I’d reverse to only blow hot. Once set, I’d disconnect any plugs to stop it from changing on its own.

Bit more work this way, not ideal, fairly easy job

I could probably spend today and have a couple dozen of them in my hands, they are out there one in each vehicle unless it's been yanked already
there are 48 compatible vehicles in just 1 yard near me about 20 minutes away and 2/3 times more 1 hour from me.
that's just 1 yard.
that rear control module failing is really not all that common, it happens but not nearly as often as you guys are perceiving