My 20 yr old pregnant daughter has a 1999 Accord EX that I bought her a couple years ago and the heater and a/c stopped working recently. Here is some info..

- Blower motor control works in all speeds
- Only blows outside temp air, can not change temp
- Replaced control head w/no change
- I have swapped all fuses with known good fuses
- I have swapped a/c clutch relay with known good relay (horn relay)
- I am not getting any lights on the control head at all. I can push all the buttons but none work and none of the lights lite up
- I checked with a meter and have power getting TO the fuses and leaving the fuses

I was thinking about the pressure sensor, but wouldn't the heater still work? Wouldn't the lites on the panel still lite up? Can anyone please help me out. It is getting hot here and she is pregnant so I really want to get this fixed but don't have a lot of money to take to a shop. Please. Thanks in advance.

 

I'll kind of summarize the testing from the shop manual. I would highly suggest buying one, you can get one for $22 as a pdf from automanualsource.com.

Check #54 fuse (40A) in under hood fuse box. Check #3 fuse (7.5A) in driver's side box. Check #13 fuse (7.5A) in passenger side fuse box.

Disconnect 22-pin connector from heater control panel. Turn key to the II position. The #2 pin (blk/yel wire) should have 12V to ground.

Turn key to off. Measure voltage from pin #3 (wht/yel) to ground.

Test for continuity to ground (~ zero resistance) on the #9 pin (blk wire).

Just to be clear and avoid confusion, all the voltage tests are are on the wire harness side btw.

 

Totally agree with what PA has posted.

My only question - you replaced the hvac control/panel with another, was it new or used? I ask because this gen had issues with the PCB in the controls........but I should have started with, is this "auto" or "manual" hvac controls?

 

PA: Thanks for info and I will check those contacts as soon as she comes back over with the car. I have a Hayne's manual but I am assuming the shop manual you are referring to is much better at fault isolation procedures. I did check fuses #3 and #13. They both look good and both have 12v on both sides of the fuse. I also checked a couple fuses under the hood but not sure about #54 specifically. Anything that said it had to do with hvac I checked and swapped fuses with known good fuses.

poorman: She has the manual hvac controls and I purchased a used one off e-bay from a reputable parts dealer ( I know that don't always mean it is a good part though). I wondered about the new part myself but what are the odds the new one would be doing EXACTLY the same thing as the old one?

Thanks for the info guys. I really do appreciate it!

 

The #54 fuse is one of the big fuses, and you would have a lot of components not working if it was blown.

Recheck those fuses and test at the HVAC electrical connector. The problem may be the wiring from the fuse box to the HVAC unit. Or the replacement part could have the same problem. Running through electrical test will narrow down the problem.

Was any work done on the car right before this problem surfaced?

That shop manual I referenced has much more detail about your specific vehicle.

 

Just me but since these had an issue with the PCB for the hvac controls I'd still call it a "possible" issue.

Do you have the old one still? It wouldn't hurt to try "jumping" the old one and install it and see what happens? See this thread: https://www.hondaaccordforum.com/for...g-50944/page3/

 

Sorry guys, I haven't had a chance to work on the car again until now. Here is what I done today.

- Checked fuse #54. It was good
- Pulled a three relays under the hood and jumped them to the battery. All clicked just as advertised.
- Checked for power at pin #22. Power was good.
- Checked for power at pin #2. It was good.
- Checked pin#9 for ground and it was good.

What does the PCB control? I ask because the blower motor works fine in all ranges but no other controls or buttons work on the panel. The rear defrost button doesn't lite up, the temp control doesn't work. Nothing on that panel works except for the blower control.

 

I can try jumping the PCB? I am not sure if that's what you meant. I also would not know what to jump. Can you advise? Thanks.

 

Look at the pictures in post #24 https://www.hondaaccordforum.com/for...working-50944/

Solder a wire between those two spots on the printed circuit board.

 

I soldered a jumper but still no change. Man, I am so lost on this one. I have good power and ground at the control until. So it seems that would be the cause. I hate to spend money on another one only to find out that doesn't fix it either.