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Discussion Starter #1
I have a 99 Accord LX. The Heater / AC Control buttons will not light up.
The fan blower works fine. The air conditioning will not come on.
The rear windshield defroster will not come on.
I have taken off the bezel and reseated the connections with no luck.
I have also checked all the fuses with no luck.
I swapped the relays in the engine compartment fuse box for the condensing fan
with the ones for the lighting system. No difference, so it seems that the relays are okay.
From what I can tell I need to replace the Heater / AC control. I do not have Climate Control.
On ebay I have only been able to find Heater / AC controls that have climate control.
Is my car capable of using the Heater / AC control that has climate control?
If yes, will the climate control work?
Or are there some missing components to the system.
 

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The heater control panel is computer controlled and has a self diagnostic function. If you have access to a Honda service manual it gives all the details. If not I believe you turn the ignition ON, Fan OFF and Recirculation switch ON. Push and hold the Recirculation button (light goes OFF) until the Recirculation light starts blinking out codes (long and short blinks). Dont ask me how to read them. You will probably have to see a dealer for that.
There are fuses under the hood #54 & #56 and in the drivers side panel #3 and passenger side panel #13. A bad ground could also be a cause.
I doubt a climate control panel will work on a standard panel car, but I really don't know.

Good Luck
 

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HunterX:

As in your '99, I have the same "Manual" HVAC controls in my '02. They are NOT interchangeable with the "Automatic" climate control system components used in the "EX" cars. And vice-versa.

Sounds like you've done all your basic homework very well. I suspect a faulty control unit, with several of your switches being defective. I am ASSUMING there is nothing otherwise wrong with your A/C system and your RW defroster.

If you can't find an ostensibly decent used one in a local salvage yard, you may have to bite the bullet for a new one from your dealer. At Majestic Honda's website, they indicate a price of $162.70. Plug in your VIN, then look under "heater controls" for the exploded diagram and cost.

http://www.hondaautomotiveparts.com/
 

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Discussion Starter #4
Thanks for the information.
I now know that the "Manual" and "Auto" AC controls are not interchangeable.
Does anyone have a wiring diagram for the Heater / AC control?
Wondering if I can jumper some wires together to see if the air conditioning will come on.
There are two harnesses on the back I figure one controls the fan blower and the other controls the temperature and control buttons.
 

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HunterX:

I strongly advise against what you are considering. Toast the wiring harnesses (and likely other electrical components) and you'll be crying some big elephant tears. (Read, ultra EXPENSIVE repairs!)

If you so care to persist, get your dealer to copy it out of the factory service manual or print it off the Honda Techline.

Sniff, sniff. Where's my fire extinguisher? I smell SMOKE.
 

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Discussion Starter #6
Update:
Bought a replacement AC / Heater Control off of ebay.
Everything has been working for a about a week.
So, I guess my original AC / Heater Control was bad.

Thanks to everyone.
 

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Update:
Bought a replacement AC / Heater Control off of ebay.
Everything has been working for a about a week.
So, I guess my original AC / Heater Control was bad.

Thanks to everyone.
I have the same problem on my Accord LX 1999. Looks like I need to buy and install a new AC / Heater Control. Could you please share the instructions for swapping this component. Thanks.
 

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I have the same problem on my Accord LX 1999. Looks like I need to buy and install a new AC / Heater Control. Could you please share the instructions for swapping this component. Thanks.
I just fixed a 2000 Accord LX with this snafu. The good news is that this is as close to plug and play for a fix as you can get.

You can look up how to access the radio for detailed directions but in a nutshell:
- Remove plastic shroud/surround in center of dash
*remove 2 screws at bottom
*FOr third scres, it's hidden behind the clock. Using a thin bladed knife (I used a kitchen knife wrapped in a paper ticcue to avoid scratshing) or screwdriver, pry the bottom of the clock out and pull the unit out. Unplug the wires and set aside. Take out 3rd screw behind in dash. Lift shroud from bottom out.
- AC control unit is mounted to the back of the shroud.
*Disconnect the 2 wiring harnesses from AC control unit.
*Remove the 5 mounting screws and remove AC unit panel.
*Before mounting new unit, lug in the 2 wiring harnesses and check operation...you should be good to go if the original part was the failure.
- Replace pieces in reverse order

Easy-Peasy...be careful and patient with those plastic pieces so you don't scratch them.
 

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I am having the same problem as HunterX and Markov314, with a twist. I have the control exposed and ready to replace and the 2 harnesses disconnected, soon as i buy one, but my compressor is turning on and off without the control being connected. Any thoughts?
 

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1999 accord ex heat conroler

i have 1999 accord ex 4 cyl . heat control is work only high speed (4), 1 2 3 it does work. any body know this problem? please help me. thank you.
 

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My father has a 2002 Ford focus that he had that problem with (The fan only working on 4) It ended up being a relay i believe. I don't know which one but i assume one of the relays for the heater or the fan.
 

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did you ever get this resolved? I have a 99 V6 coupe and the only thing that always works it the fan speed. The A/C only comes on intermittently and I get lucky if I can get it to switch from cool to hot air. Sometimes the lights come on but once they go off, the only thing that works is the last setting it was on and the fan speed.
 

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Hi folks,

I had the same problem and took apart the heater control module to see if I could fix it before dropping $300 on a new one-- in fact, mine was fixable with one jumper wire and a soldering iron. Read on.

Symptoms:
Only the blower motor speed knob worked. None of the vent buttons, A/C button, or the lights work.

Quick solution:
On the underside of the board, just jumper the input (leftmost) leg of the 78dl05 voltage regulator in the middle of the board to the positive leg of capacitor C1. That's it.

Long story:
Since the whole panel went dead all of a sudden, with nothing working, I pried open the module with a small flat head screwdriver, and pulled the knobs off.

I tested the 5v regulator which supplies 5v power using the 12v from the battery. The part is 78dl05 and it is in the middle of the board.
It was not outputting 5v, so I next checked if it was receiving 12v.
Pin 1 Input (12v)
Pin 2 output (5v)
Pin 3 Common (ground)

Pin 1 of the harness is +12v, and the ground pin is in the very middle all by itself. The board was receiving +12v. So that means that there is an open circuit somewhere between the regulator and the connector.

So I traced back from the input leg of the 78dl05 to the connector CN1. The first through hole was covered in greenish blue corrosion. It is located underneath a rubber strip directly below the 78DL05, which is why I didn't spot it immediately. I wouldn't be surprised if this is how most of these boards fail.

The only other thing between the input leg and the connector CN1 is a capacitor, C1. It looked fine (wasn't burst or leaking). I could have attempted to fix the through hole in the board, but it would likely die again, so I decided to just jumped the input leg to the capacitor, which provides a handy place to solder to.

I jumped the positive side of C1 to the input leg of the 78dl05 (left most leg, labeled in+ on the top side of the board) and then plugged it back into the harness, turned the car on, voila, all works fine.

$293 for the part from the Honda dealer and probably $100 more in labor-- you can do it yourself in 15 minutes if you have a soldering iron ($12 from Radioshack) and a couple of screw drivers. Stupid simple.

I just fixed a 2000 Accord LX with this snafu. The good news is that this is as close to plug and play for a fix as you can get.

You can look up how to access the radio for detailed directions but in a nutshell:
- Remove plastic shroud/surround in center of dash
*remove 2 screws at bottom
*FOr third scres, it's hidden behind the clock. Using a thin bladed knife (I used a kitchen knife wrapped in a paper ticcue to avoid scratshing) or screwdriver, pry the bottom of the clock out and pull the unit out. Unplug the wires and set aside. Take out 3rd screw behind in dash. Lift shroud from bottom out.
- AC control unit is mounted to the back of the shroud.
*Disconnect the 2 wiring harnesses from AC control unit.
*Remove the 5 mounting screws and remove AC unit panel.
*Before mounting new unit, lug in the 2 wiring harnesses and check operation...you should be good to go if the original part was the failure.
- Replace pieces in reverse order

Easy-Peasy...be careful and patient with those plastic pieces so you don't scratch them.
 

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Just curious, my control works just fine, but sometimes the backlight for the temperature control won't come on after starting the car, and sometimes it's the backlight behind the 3 bottom buttons (recirc, A/C/, and rear defrost). The LEDs for the buttons still work, and the function of the temperature dial still works, just the lights won't come on. However, a light knock on the right side of the the dashboard, just to the left of the glovebox, will bring the lights back on. Is this a related thing? It never really bothered me much since all it took was a knock next to the control to get it to come back on, and even if it was off, the control still functions.
 

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Thank you, hybridmojo! Brilliant fix.

I pulled my panel out and started looking at it. I have quite a few other bad throughholes from the top rubber piece. That might explain why my LEDs have either been going out, or sometimes stay on very faintly even when the key isn't in the ignition. I'm not sure it's worth trying to fix those. A lot of the bad through holes are right next to the microchip on the board. Any idea what that chip controls? If I had to guess, it's what sends the signals to the climate control system to change the temperature, the vents and light up the correct panel light. It's really hard for me to figure out what tracings go where with some of the corrosion to the surface of the PCB. Sigh.

All the same, I'm going to attempt your fix. I also have corrosion on that same through hole you did, and I'll see what happens.

[UPDATE]:
So I did the soldering, and attempted to scrape off some of the corrosion that existed in other spots. I think that was a pretty dumb move. Now the blower speed light doesn't work, nor do any of the backlights for the buttons--but the LEDs still work! I don't get it. Also, the temp control light still works.

I'm not sure if my scratching at the corrosion caused it, or if just handling the board caused the lights to break.

Regardless, I'm still testing the panel. The problem is that it's not something that happens every time I use the car. Sometimes it works for days... others it's broken for weeks. Sometimes it flickers constantly. We'll see, but so far it's SOLID.
 

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Thank Hybridmojo, I am new to the boards here but I pulled my unit out and did the repair as instructed by the description and pics and my 99 Accord LX works perfect. Thanks save me a bunch of money on a new one.
 

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I just fixed a 2000 Accord LX with this snafu. The good news is that this is as close to plug and play for a fix as you can get.

You can look up how to access the radio for detailed directions but in a nutshell:
- Remove plastic shroud/surround in center of dash
*remove 2 screws at bottom
*FOr third scres, it's hidden behind the clock. Using a thin bladed knife (I used a kitchen knife wrapped in a paper ticcue to avoid scratshing) or screwdriver, pry the bottom of the clock out and pull the unit out. Unplug the wires and set aside. Take out 3rd screw behind in dash. Lift shroud from bottom out.
- AC control unit is mounted to the back of the shroud.
*Disconnect the 2 wiring harnesses from AC control unit.
*Remove the 5 mounting screws and remove AC unit panel.
*Before mounting new unit, lug in the 2 wiring harnesses and check operation...you should be good to go if the original part was the failure.
- Replace pieces in reverse order

Easy-Peasy...be careful and patient with those plastic pieces so you don't scratch them.
I want to remove the same part inorder to troubleshoot/replace-if-necessary the A/C Ctrol Unit. I am not to ggod working with those plastic parts. Is there any hidden plastic clip or any special trick that I need to be aware of, other than the thre screws that need to be removed?
 

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the fix doesn't work for me

Hi,
I have a 98 accord 4dr LX. in 205 i replaced my original climate control with a one I've at the junkyard, it lasted 4 years, The in 2009 i did it again - replaced the unit with a used one from a junkyard. Now that one broke too.. So now i have 3 broken units so, when I found your post I did what you recommended to 2 of the units, both worked for about 1 day and now are again inoperable. I am sure I connected the jumper wire to the correct places shown. As a note one of the units did have the burned mar in the exact place you show but the second one didnt'. Anyway, I am still looking for a solution but looks like I'm going back to the junkyard for the 4th climate control unit, good thing is they cost only $30 a pop. And if there is anything else that I can do to these boards to fix them please let me know, and thanks for all the informative posts everyone, Konrad.
 

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did you ever get this resolved? I have a 99 V6 coupe and the only thing that always works it the fan speed. The A/C only comes on intermittently and I get lucky if I can get it to switch from cool to hot air. Sometimes the lights come on but once they go off, the only thing that works is the last setting it was on and the fan speed.
that's the same exact problem I'm having.. You even get it fixed?? ****s in the winter cuz half the time it's stuck on cold air on the highway in the winter.. Any solution besides replacing the damn thing??
 

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Just fixed mine, same symptoms.
Fan blows but non of the buttons react and no leds
once the board was out of the housing it works just fine and all checks out, however when installed back..same thing, finally I figured (by trial and error) that its the plastic back cover! installed it without it (using the same screws)
and it works just fine.....crazy? maybe, but it works!
 
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