Need Help With Climate Control

[Tom]

Thanks so much, Tom! So, I actually have a degree in electronics engineering. However, that was what feels like a billion years ago and I have done very little of it since then - I've been in software for my whole career - so I "get it", but I'm super rusty when it comes to application of that ancient knowledge. If I could figure out how to get the three PCBs apart and off of the clear front plate, I think I'd feel a lot more like I can handle this

I mean, if you have time and the inclination to take a whack at it, I'm happy to send it to you, I just feel bad asking for the help because somewhere in the dusty corners of my mind is all the knowledge to handle this myself..

I suddenly feel conspicuous giving electronics troubleshooting advice to an EE. However, I feel my finance and law degrees have prepared me to give this advice, so I'll charge on.... Totally up to you if you want to dig in. If you'd rather send to me, might be best to remove the clear plastic first, so you can break it yourself and I won't need to feel guilty about it. On my car, mine is cracked several times over, but I use clear packing tape to hold it together and that's been working for nearly 2 decades now....

Definitely don't feel too conspicuous - I went to DeVry In total fairness, I actually think I got a great education there, but I haven't used it in so long that I honestly remember very little. Plus, they teach you how to design circuits, not how to troubleshoot broken ones . Your practical experience with this CC unit is worth exponentially more than my ancient and dusty degree - and definitely in this context.

RE: Getting the clear plastic thing off - should I just commit to breaking it? It appears to be held in place by the AC and Defrost/Recirc buttons and those look to be soldered in place. From what I can tell, breaking it is about the only option... any tips or tricks from your experience?

RE: Voltage on the 11V rail - Nope. Well, not entirely nope - I'm getting ~0.28V, but I think that qualifies as 'nope' where 11V is expected.

I'm still leaning the direction of sending this to you, if you have the time to have a look at it - I've just spread myself too thin as of late and so this is 'just one more thing', if you know what I mean

Sounds like something is trashed on that voltage rail. You might just try replacing that capacitor and seeing if you get lucky. I'm trying to remember, but I 'think' the safest way to get the clear plate off is to remove (desolder) the snowflake (a/c) and the defrost/recirc button (both a pain). Even then, there's no guarantee on not breaking it. It's on the back burner, but I have always meant to come up with at 3D print for that clear plate. Someone else did it a while back, but I think with the new resin printers, we could make a more polished version. Totally up to you if you want to send it to me. PM me if you want to do that. I'm slow, and no guarantees on the clear plate (or even getting it working), but I suppose it's not that much use the way it is, so not a huge risk really....

[crackership]

I suddenly feel conspicuous giving electronics troubleshooting advice to an EE. However, I feel my finance and law degrees have prepared me to give this advice, so I'll charge on.... Totally up to you if you want to dig in. If you'd rather send to me, might be best to remove the clear plastic first, so you can break it yourself and I won't need to feel guilty about it. On my car, mine is cracked several times over, but I use clear packing tape to hold it together and that's been working for nearly 2 decades now....

Definitely don't feel too conspicuous - I went to DeVry In total fairness, I actually think I got a great education there, but I haven't used it in so long that I honestly remember very little. Plus, they teach you how to design circuits, not how to troubleshoot broken ones . Your practical experience with this CC unit is worth exponentially more than my ancient and dusty degree - and definitely in this context.

RE: Getting the clear plastic thing off - should I just commit to breaking it? It appears to be held in place by the AC and Defrost/Recirc buttons and those look to be soldered in place. From what I can tell, breaking it is about the only option... any tips or tricks from your experience?

RE: Voltage on the 11V rail - Nope. Well, not entirely nope - I'm getting ~0.28V, but I think that qualifies as 'nope' where 11V is expected.

I'm still leaning the direction of sending this to you, if you have the time to have a look at it - I've just spread myself too thin as of late and so this is 'just one more thing', if you know what I mean

Sounds like something is trashed on that voltage rail. You might just try replacing that capacitor and seeing if you get lucky. I'm trying to remember, but I 'think' the safest way to get the clear plate off is to remove (desolder) the snowflake (a/c) and the defrost/recirc button (both a pain). Even then, there's no guarantee on not breaking it. It's on the back burner, but I have always meant to come up with at 3D print for that clear plate. Someone else did it a while back, but I think with the new resin printers, we could make a more polished version. Totally up to you if you want to send it to me. PM me if you want to do that. I'm slow, and no guarantees on the clear plate (or even getting it working), but I suppose it's not that much use the way it is, so not a huge risk really....

I just found a small bag of 47uF electrolytic capacitors in my old college junk.. I knew I was holding on to all this crap for a reason! they're the 50V variant but it should be ok to at least prove out whether or not replacing the cap is enough to get it working again.

By chance, do you know what the polarity of the one in there is? I can't see any markings on the body and, of course, the legs are cut even so I'm not sure which end is +.

[crackership]

[Since you said you took that schematic and pic from RL, I deleted them out of an abundance of caution.
For reference, it looks like it came from this thread: https://rennlist.com/forums/924-931-944 ... atics.html --Tom]

Between the two, I think the polarity is pretty evident.

Based on the schematic, though, having just C1 blown shouldn't kill the 11V rail - I believe that capacitor is just a shunt to ground. I'm going to poke around at it a bit more to see if I can figure out where the circuit is broken.

Another question - so the one thermistor that seems wonky for me is under the hood - where are the other two?

[Tom]

Sorry I missed your question. Just looking at the traces underneath, it looks like the lead closest to the vertical circuit board is the negative side. Be careful with that schematic -- not really sure where it came from or how accurate it is, but more importantly, there are several versions of the board, so that schematic may not match the board you have. Note, for example, that the picture of the separate board you just posted doesn't match the picture you took of your own board. Notice the big blank space under the capacitor in question...and compare that to your board. I agree that the cap probably blew as the result of something else going bad, although if it shorted out, then it would kill an otherwise 11v rail... (and probably a fuse).

On the thermistors, one of them is clipped to the top of the heater core box and very easy to get to when you take the vents out of the dash. The other is clipped to the US-passenger side of the heater core box. See factory manual pic below (#4 & #5).

Looking forward to what you find. I 'believe' I have all the chips used on the board, if you conclude any of them burned out. A few are easy to find, but the motor driver chips are nearly impossible to find. I can also check signals on a working unit if helpful to know what you "should" be seeing at various points. A lot of times, that's how I figure out what's bad...

hvac factory page.jpg (179.13 KiB) Viewed 2606 times

[crackership]

Thanks again, Tom! You're an absolute legend!

Some new developments this evening:

First, I carefully desoldered the capacitor that fried from the CC unit. Turns out the capacitor got hot enough to burn a hole in the circuit board and so there's nothing but a gaping black hole where there should be the two holes for the capacitor legs to poke through - all of the circuit board trace there is gone. I think that means it's dead.

Then, just to think about something else, I went out to my shed of car parts to rummage around for something else and lo-and-behold, there was another CC unit. I have no memory of acquiring this, but I figured "hey, it's probably dead too, but if it's dead differently I might be able to make one working unit out of the two!" So I took it back to my garage, plugged it into the car and wholly potatoes, it works!!

I guess it pays to hoard car parts..

So, energized by this victory, I pulled that thermistor out from under the hood and checked it on the bench - It still thinks it's ~50F. I promise it's not 50F here. It is quite a lot warmer..

Looks like Digikey is out of stock on these guys but Mauser has them.. of course Mouser wants a dollar more than Digikey.. highway robbery

Overall, good day in the garage - hopefully one $4 thermistor and it will all be back to normal!

Thanks all, and definitely thank you @Tom for all your help!!

[Tom]

Thanks again, Tom! You're an absolute legend!

Some new developments this evening:

First, I carefully desoldered the capacitor that fried from the CC unit. Turns out the capacitor got hot enough to burn a hole in the circuit board and so there's nothing but a gaping black hole where there should be the two holes for the capacitor legs to poke through - all of the circuit board trace there is gone. I think that means it's dead.

Then, just to think about something else, I went out to my shed of car parts to rummage around for something else and lo-and-behold, there was another CC unit. I have no memory of acquiring this, but I figured "hey, it's probably dead too, but if it's dead differently I might be able to make one working unit out of the two!" So I took it back to my garage, plugged it into the car and wholly potatoes, it works!!

I guess it pays to hoard car parts..

So, energized by this victory, I pulled that thermistor out from under the hood and checked it on the bench - It still thinks it's ~50F. I promise it's not 50F here. It is quite a lot warmer..

Looks like Digikey is out of stock on these guys but Mauser has them.. of course Mouser wants a dollar more than Digikey.. highway robbery

Overall, good day in the garage - hopefully one $4 thermistor and it will all be back to normal!

Thanks all, and definitely thank you @Tom for all your help!!

That's awesome and thanks for the kind words. We are living opposite lives. You can't remember buying spare parts but find them when you need them. I remember buying spare parts but can never find them when I need them. Glad you got the car working! Somewhere in all my unfindable parts collection, I have a few cc units with the boards separated. If you want to try replacing that board, I can take a look for one. Since you are a parts-saving guy, I'd definitely hold on to the fried unit either way -- never know what you might need from it in the future. Or I'm still happy to see if I can get it going.

[crackership]

Thanks again, Tom! You're an absolute legend!

Some new developments this evening:

First, I carefully desoldered the capacitor that fried from the CC unit. Turns out the capacitor got hot enough to burn a hole in the circuit board and so there's nothing but a gaping black hole where there should be the two holes for the capacitor legs to poke through - all of the circuit board trace there is gone. I think that means it's dead.

Then, just to think about something else, I went out to my shed of car parts to rummage around for something else and lo-and-behold, there was another CC unit. I have no memory of acquiring this, but I figured "hey, it's probably dead too, but if it's dead differently I might be able to make one working unit out of the two!" So I took it back to my garage, plugged it into the car and wholly potatoes, it works!!

I guess it pays to hoard car parts..

So, energized by this victory, I pulled that thermistor out from under the hood and checked it on the bench - It still thinks it's ~50F. I promise it's not 50F here. It is quite a lot warmer..

Looks like Digikey is out of stock on these guys but Mauser has them.. of course Mouser wants a dollar more than Digikey.. highway robbery

Overall, good day in the garage - hopefully one $4 thermistor and it will all be back to normal!

Thanks all, and definitely thank you @Tom for all your help!!

That's awesome and thanks for the kind words. We are living opposite lives. You can't remember buying spare parts but find them when you need them. I remember buying spare parts but can never find them when I need them. Glad you got the car working! Somewhere in all my unfindable parts collection, I have a few cc units with the boards separated. If you want to try replacing that board, I can take a look for one. Since you are a parts-saving guy, I'd definitely hold on to the fried unit either way -- never know what you might need from it in the future. Or I'm still happy to see if I can get it going.

I'm definitely in your reality more often than this crazy alternate universe I experienced last night - my parts collection is not what I would call "organized" and some of those parts are pretty big so they tend to obscure the smaller stuff I might actually use. For instance - do you know anyone who needs a door for an Alfa Romeo GTV6? I have three of them. I mean, I do have a GTV6, but I figure the likelihood of needing three extra doors is low. They're super in the way and heavy, but they were free and they're unobtanium if you actually need one.. It's just nice to know that collecting parts for a couple decades payed off once

[stitch2k1]

Minor necro, but related to HVAC panel repair.

Does anyone remember who had 3D printed files to repair the acrylic parts of the panel?

[Tom]

Minor necro, but related to HVAC panel repair.

Does anyone remember who had 3D printed files to repair the acrylic parts of the panel?

If you mean the clear piece that always cracks, @Rennbay Travis mentioned to me a while ago that he has a perfect STL, or has access to one. I've seen a few attempts to print them in 'clear' FDM filament, but that was before resin printers became affordable. With clear resin on a resin printer, I bet we could make them look near-factory. For reference, the 'glass' tubes in my Flux Capacitor came right off my FormLabs resin printer....

[Rennbay]

@Tom injection molding? I went ahead and bit the bullet on tooling. It's funny you tagged me now. This is a teaser of a pre-production sample. It's been in hand for a total of 3 days now. Top one is 35 year old OE, bottom is the new one.
The tool needs to be polished better in some areas but the fit is amazing. Looking at having new ones for sale sometime in the next 30 - 60 days.

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