Opening Up and Fixing The Dash-Mounted A/C Control Unit???

[NSXTC]

OK, here’s one for the hard-core techies…

My climate control fan either blows next to no air, or full blast- there is no in between. My local Acura tech here thought it was the blower motor transistor, even though I have a ’94, and the TSB in question was only for ‘91’s. We tried a new transistor and that did not fix it. Subsequent testing indicates that the A/C control unit (IOW the dash-mounted component above the stereo) is bad.

This unit is big $$$ from the dealer. I guess we could get one used from ERZ or somewhere like that, but who’s to say it won’t happen again.

There are no published schematics for this unit. I’d be willing to bet that there’s a single electronic component in there like a resistor or something that can be replaced with a like component from Radio Shack and make it work as new.

Has anyone with this problem ever bravely plunged forth into this unit and figured out how to fix it??

This is a very obscure operation, even the dealers don’t do it, they just replace the whole control unit, so im not expecting that anyone out there in forums land has any insight on this, but you never know. I thought it might be worth a try to ask, and if we can figure this one out, it may be worthwhile to add to the FAQ.

There is a reference in this thread to having some capacitors replaced:
http://www.nsxprime.com/ubb/Forum10/HTML/000641.html

Am trying to find out more from that user, but if anyone has better specifics, please post here.


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All My NSX'es Live in Texas

[This message has been edited by NSXTC (edited 21 October 2002).]

 

[4AU4LIFE]

Please do use the favor of posting the results if you are able to repair it.

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ALL NSX
92 RED/BLACK 5-SPEED

 

[chudson1549]

I replaced mine from EZcars and he told that there are a min. of three that need to be replaced. He didn't tell me which ones. However, after trying the transistor with no results, it works great now for about $300

 

[NSXTC]

I was able to get the name and email address of the electronics guy who fixed a control unit of a forms member recently. I asked if he could post the solution directly to this thread or email back to me how to do it. I'll post whatever I get back from him. Apparently, he replaced 3 capacitors inside the unit, but that's all I know. I hope we will get the "whole story" with radio shack part numbers, etc. It will make a good Do-it-Yourself procedure....

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All My NSX'es Live in Texas

 

[chudson1549]

Originally posted by NSXTC:
it. I'll post whatever I get back from him. .....Do-it-Yourself procedure....

Please do, I have my original in the attic in real good condition other than the board.

 

[NSXTC]

Im going to probably take mine out this weekend if time permits. If I can figure it out and get it to work again, ill take some pictures, and try to put together a detailed DIY.

Gerhard (the guy who has fixed them in the past) was kind enough to email back what he had to do to fix Michael's climate control unit:

The problem we found on Michael's control was leaky and dried out electrolytic capacitors. We replaced the defective capacitors and repaired the damaged traces. Anyone wanting to do this will need a
reasonable amount of electronic knowledge and some good soldering equipment.

Assuming that you know what electrolytic capacitors are and understand their markings, look for discolored (usually black) areas around the components. Carefully remove (unsolder) the defective capacitors noting their values and polarity. Then using an Exacto knife and fiberglass
brush (or equivalent) scape back all the effected solder resist.

Thoroughly remove any corrosion and clean the areas. Repair or rebuild the traces. Install new capacitors.

If you don't understand what I just wrote or if you lack proper tools and experience with soldering electronic components, I would suggest you take it to someone who does rather then try to fix it yourself. We did
the repair on Michael's for $100 plus tax and would consider doing the same on a ship in ship out basis for your people in your group.

I hope that helps.

Gerhard Langguth
LANGGUTH Electronics Inc.
711 East Parkway Inc.
Russellville, Arkansas 72801
(479)967-0873


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All My NSX'es Live in Texas

 

[BadCarma]

just a thought as I am going to diy my own climate control head.BUT I am not going to replace the obvious bad caps only.my thought on this is I have heard of guys with a few bad caps and others with many bad caps.they are so cheap and I am mil and nasa spec certed for componant level work so it will go quickly (the repair) I will replace all the caps good and bad.I think it wise as you are doing it anyway.its not that much extra work and it would be a real bummer if you replaced only the current bad caps and some others go south just a short time down the road.anyone agree with this?
david

 

[NSXTC]

I guess......I haven't opened the unit up yet, so not sure what it will look like in there. I was going to do it this weekend, but not sure if I will have enough free time.

What's your timeframe for posting pics and the DIY procedure?

Originally posted by BadCarma:
just a thought as I am going to diy my own climate control head.BUT I am not going to replace the obvious bad caps only.my thought on this is I have heard of guys with a few bad caps and others with many bad caps.they are so cheap and I am mil and nasa spec certed for componant level work so it will go quickly (the repair) I will replace all the caps good and bad.I think it wise as you are doing it anyway.its not that much extra work and it would be a real bummer if you replaced only the current bad caps and some others go south just a short time down the road.anyone agree with this?
david

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All My NSX'es Live in Texas

 

[BadCarma]

I am planning on doing it next weekend when i install my new seats and another beta nos kit i am building.as for time frame:
30 minutes to remove head
30 minutes to disassemble head
30 minutes to test
30 minutes to desolder caps
30 minutes to clean and prep board
unknown time to procure new caps (will get them in advance most likely)
1 hour to rebuild
30 minutes to reinstall
I think the caps (all of them will cost around 10 bucks)
est time total 4 hours taking my time
thats if murphy dont come calling
david
ps i will tape the procedure and make it available like the window fix it tools.it can just float around the community and people can copy the heck out of it so that should help out.if i dont do it next weekend god knows when i will find the time as i am in a giant xp roleout at work and i will be coordinating it nationwide

 

[NSXTC]

Sweet!!

Ill wait another week and do mine following your instructions. Drop me an email when you get it done.

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All My NSX'es Live in Texas

 

[BadCarma]

Originally posted by NSXTC:
Sweet!!

Ill wait another week and do mine following your instructions. Drop me an email when you get it done.

NSXTC, I did not do the fix this past weekend as expected.I bought a bunch of stuff and am waiting for it all to arrive to do it all at once.I will be removing my oem seats and installing a dali harness bar, race seats with scroth restaints and taitec mounts, type r carbon fiber shift boot and gruppe m shifter and a new nitrous array in the center console where the phone used to go.as I will be re routing my nos wiring,I will have the seats out and that is the time to remove the center console do all my mods and fix the head unit all in one weekend.I will keep you posted as I really want to post a diy repair for the ac unit.to many older cars are coming down with this issue and I would like to see us all save a bunch of cash so it is still on my plate.I will post as soon as I get her done
david

 

[NSXTC]

No problem...Ill catch you after NSXPO.

 

[T Bolen]

Hey guys - I'm now starting to experience weird operation of my AC fan. Upon first starting the car it does not want to run unless you set the switch on high. Any settings below that it either does not work or it is intermittant. After a short while, it will then start working normally.
Is this related to the capacitor problems as described in this thread?
I'm OK with doing electronic work and would be interestered in attempting this.
Bad Carma - I'm across the pond here in Tampa. Private me if you want to try this as a team.
Tom

 

[NSXTC]

Hey kids, the fix is in!!!

For all those of you whose climate control fan only blows full speed or none at all.

Well, I had some this weekend to mess around in the garage and I figured I might as well get the blower motor control unit pulled out and maybe take a look inside. I wound up fixing my blower control, so now I can vary the fan speed again..

It was all very easy to open up. Only 3 screws holding the control unit together. Per Gerhard’s advice, I looked at the electrolytic capacitors on the main board for the telltale discolorations, and sure enough!

The culprit was a 47uF 50v electrolytic capacitor worth $0.05! Of course Radio Shack sells them for $0.99, but I don’t mind the markup so much!

The capacitor in question sits right above four power transistors, which I believe control the voltage to the blower fan.

Many people have paid $3-$500 to simply swap the entire control unit, which is what the service manual says to do if your diagnosis traces the problem back to the control unit.

Like the Bose stereo amplifier issue, this A/C control unit issue is one that many owners have experienced, and it will probably happen to all of us in time.

Here’s how to save $499.01 and fix the little bugger yourself:

1. Before starting, make sure that your problem is not caused by the fan motor TSB and follow the troubleshooting flowchart in the service manual to be sure that your problem lies in the control unit and not elsewhere in your climate control system.

2. Remove the center console (I believe this procedure is written up in the FAQ)

3. Remove the blower motor control unit from the car – 4 screws and two wire connectors

4. Remove the two little countersunk Phillips head screws on either side of the control unit

5. remove the larger round Philips head screw at the rear of the unit.

6. unsnap the front to the control unit from the back

7. remove the black plastic square piece that secures the main board inside its enclosure

8. slide the main board out of the enclosure

You should now be looking at this:

9. Remove the old one and re-solder a new 47uF 50v Cap as shown in the picture. If you are not comfortable with soldering small electronic components, I highly recommend you contact Gerhard who will do it professionally for $100. His number is (479)967-0873. It is very easy to mess up the small traces on the PC board, and then you will have no choice but to buy a new control unit ($500) or a used one ($300)

10. Re-assemble and re-install control unit

That’s it… I can't guarantee that this will fix the problem on your car, but it did the trick for me..you owe me a drink if this works for ya!! <;-)

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All My NSX'es Live in Texas



[This message has been edited by NSXTC (edited 17 November 2002).]

 

[nicholas421]

Originally posted by NSXTC:
Hey kids, the fix is in!!!

you're the greatest!!! thanks

 

[Larry Bastanza]

Cool,

That is really good.

Lud,

Maybe we can post this in the FAQ DIY section. And of course I officially nominate Mark again for the Comptech contest.

Thanks,
LarryB

 

[subwaysam]

Didnt' work for me..did it today...we replaced a total of 3 of them...they all looked real bad....(capacitors)..still high speed only.

Also, only found 35wvdc capacitors at the Shack,.. they told me that is all they carried..even got the big catalog out...

35wvdc should be ok (vs the 50 taken out) as the car is at 12v anyhow...is this accurate or flawed?

 

[NSXTC]

Hey Larry - thanks for the nomination!

subwaysam- First off, you know for sure that your problem is in the control unit, right? If so, read on. I also used the 35v replacement cap from RadioShack. The OEM is indeed 50v - at least the one cap I replaced was, although others on the board have different capacitance and voltage values. I don't have any guage on your electronics skill (im just an ex-heathkit hobbyist myself) so please don't take any of this the wrong way if you already know the basics: You have to be sure that you are matching up each properly (although the voltage difference between 50 and 35v did not seem to be a problem). As long as the capacitance value is correct, it should work. Double-check the capacitance values and the polarity of each cap. The Radio Shack caps have the negative side marked with a white bar on the cap itself. I'd also advise you that you need to be sure that the trace on the TOP of the circuit board - off the positive side of the cap is soldered correctly, as well as the bottom. My initial test before I re-installed the unit was a failure until I re-examined my soldering job and found that I only soldered the bottom.

You might also have more bad caps? I know that Gerhard replaced three that he found were bad, but there are like 7 or 8 in total, most with differing values. I only had to replace one, so that could be an issue on your particular unit that I did not have.

Please let me know your result.

Originally posted by subwaysam:
Didnt' work for me..did it today...we replaced a total of 3 of them...they all looked real bad....(capacitors)..still high speed only.

Also, only found 35wvdc capacitors at the Shack,.. they told me that is all they carried..even got the big catalog out...

35wvdc should be ok (vs the 50 taken out) as the car is at 12v anyhow...is this accurate or flawed?

[This message has been edited by NSXTC (edited 18 November 2002).]

 

[DannyC]

I am getting mine done today. I will let you know. Also, what are the settings as fas as -1.5,1, or +1.5 on the outer shell of the control panel. What do I set it to?

Regards,
Danny

 

[Larry Bastanza]

Hey Guys,

Based on the fact the capacitor has polarity (+/- sides) it is an electrolytic capacitor. Using a capacitor of a LOWER voltage rating is really not a great idea. They will work for some time, but probably fail over time. Actually in this case since the 50v caps seem to fail, I would consider a higher voltage replacement. (the challenge with this idea is packaging, since they may just be too big.) The +12 volts is not the issue, but rather it is the potential voltage "spikes" that can occcur at high frequencies and current surges that will kill these babies. I also recall someone talking about "military" grade, which is really a better choice.

Also you really cannot make assumptions that the climate control is the problem, as Mark pointed out in the beginning, when he mentioned the TSB review. This is a fairly complex unit and there are many items that can fail, and probably show the same, or very smiliar symptoms.

I see 11 or so caps on the small picture above. These can ALL be suspect. Mark also mentions the "repair quality" which is so important for a lasting/proper repair. If you are going to attempt this, you really need to know about the following items:

1. Can you distinguish a "cold" solder joint from a good one?

2. Do you understand about the "wicking" properties of printed curcuit boards?

3. Do you understand what multi-layer PCB's are?

Please don't get me wrong, I am not suggesting anyone does not understand these things, but as a person formerly "in the business" of PCB design, fabrication and repair, this takes some finesse and experience.

I do not want to discourage anyone from attemping this, but as usual DO YOUR HOMEWORK, before you start. As with most things, once you start to understand about them, they are more complex then they appear on the surface.

This also takes the proper equipment. If you have a "Weller Soldering Gun", that is made to solder wires together the size of a small tree branch

, you should not even start this. A good soldering "pencil" is temperature controlled, with a fine tip.

As an alternative, sending it out could be the best $100 you ever spent. The real downside is without the proper experience and equipment you could take a good repairable PCB and render it useless.

There are a ton of sources BTW for elctronic components, military or otherwise. I have not "surfed" recently for them, but it should be easy to find on the internet.

Good Luck,
LarryB

 

[DanO]

Originally posted by Larry Bastanza:

There are a ton of sources BTW for elctronic components, military or otherwise. I have not "surfed" recently for them, but it should be easy to find on the internet.

I get my goodies from Mouser Electronics www.mouserelectronics.com

DanO

 

[BostonNSX]

what about if its not working at all

 

[NSXTC]

The DIY procedure explained on this thread is an advanced procedure that even the dealers don’t know how to do. I suggest that unless you really know what you are doing, you avoid attempting this procedure. If you aren’t even sure about what the problem with your climate system is, then you really ought to bring the car to your nearest dealer to have it looked at and diagnosed.

Originally posted by BostonNSX:
what about if its not working at all

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All My NSX'es Live in Texas