GM Bob

Repaired a friends "light display" issue on his 98 (thanks by the way to the forum for that) and when put back together the fan speed switch works sometimes, and one half on the car (drivers side) responds to the controls and the passenger side does not. It has a dual control system obviously. A few lights are out on the control unit but that shouldn't matter....right? Different circuit....right?

A swap of the head unit from a "working" 98 does the same thing in the "broken" car and the "broken" car's head unit works fine in the "working" 98. Gives me a headache just explaining it. Could it be in the harness or some other control module? By the way harness SEEMS fine.

Help me so my friend doesn't think I screwed up his car by fixing his display. Which I have done successfully several times before. Just not for my best friend.
GOD I HATE ELECTRICAL PROBLEMS, REALLY I DO!!!!!!!!!!!!!!!!!!!!
THANKS

Bill Curlee

Bob

What DTCs are present??

Have you tried to clear them and see if they come back. The HVAC system is sensitive to set DTCs. Sometimes just having one set will prevent it from working correctly. Just clearing then can return it to normal. Make sure that the HVAC system is OFF when you clear them.

If you have one set and clear it, you should be able to hear the servo motors cycle through their ranges,

BC

GM Bob

Forgot to mention
1) no codes in the computer.
2) one of the pressure sensors for the wheels seem to be malfunctioning as well, can't imagine they're related.

Could this be one of those ground gremlins?

sneakelman

I'm having the eaxct same problem in my 98. Happened after a battery change. My drivers side actuator for the blend door isn't working, and the fan doesn't respond correctly. You can watch the actuator not move when you change the temp settings. I pulled my head unit, checked all the connections, everything looks fine. What I am thinking is that so long as the actuator isn't working properly, it isn't allowing the had unit to control fan speed , because of the codes it throws. If the HVAC system isn't in proper order, it checks itself each time the car is powered up, it won't work correctly, fan, temp.
So, I ordered a new actuator from Gene Culley and will be putting it in soon as it gets here. Will let you know how things work out.
And, a BIG thanks to Bill Curlee for all his help with this matter.

DRR

You can try to resequence the blend door actuators. Either pull both leads off the battery and then hold them together for 30 sec, or pull the hvac fuse in the pass footwell and reinstall it. You will hear the doors open and close 6 times to relearn position. Either method works.

Sneakelman - How do you get to the actuators? What has to be removed?

sneakelman

To get to the drivers side actuator, all you have to remove is the panel under the steering column. The passengers side, you have to take the dash pad off.
You need to be pretty flexible to do the drivers side without pulling the dash pad, but if you can lay up-side down in the floorboard, then it's fairly easy to replace.

Bill Curlee

No problem! Anytime! Here are some pictures of the Actuator on a removed HVAC unit just so you know what they look like and how to remove them:

Passengers side:








Drivers side:







The canisters with brightly colored hoses on then are damper doors that control modes and vent positions. The small flat square/triangle shaped modules are the electronic actuators.

BC

ICUALL

There is a control module for the dual climate control, it is under the passenger side dash. You have to remove the panel under the glovebox and it is up in the corner hehind the heater blower motor.

sneakelman

Hey Bob,
replaced the drivers actuator(the one throwing codes) and it fixed everything that was going wrong.
Mine was doing the same things you describe, plus the fan wouldn't respond to commands from the control unit. Is yours doing the same thing?
Mine was easier to diagnose, as you can actually see the actuator on the drivers side, if you lay on the floorboard.
Pull up the codes on the DIC. If you are getting codes for the right side actuator saying they are open to ground, and open circuit, then my bet is the actuator is bad.
When we pulled the old one apart, the main gear inside was broken in half. My bet is that yours is the same way. Worth a check.

FLORIDA

I have a 1998 with 171,000. It is throwing codes; B0363, B0365 and B0367. Indicating left and right side actuator feedback. Right side actuator feedback code is both open circuit and open ground. I had heat on the passenger side and a/c on the drivers side. The next day the fan control won't respond until I set it at 60 degrees and tried the auto button several times. I have always had the codes but I just changed the battery. I have had the dash off before when I was bored. It was not difficult but it took a while. I will try the battery trick first. I plan to climb under the dash Saturday. What was the part number and price.

sneakelman

The part number is #89018365, actuator. Got it from Gene at gmpartshouse.com, price 148.51 shipped to me. The left and right are both the same part, and part number.

FLORIDA

ICUALL - What were your codes? You replaced the control module on the dual climate. What is that part number and the price?

ICUALL

The info I have is for a 2000 Corvette - Part Number 52479971

Gene has them available for $126.90

http://www.trademotion.com/partlocat...&siteid=214638

FLORIDA

What codes did yoy have?

FLORIDA

1) When you talk about the broken gear inside, are you talking about the feedback unit?
2) p/n?
3) Is this what corresponded to codes of B0363, B0365, B0367?

sneakelman

The gear is inside the actuator.
This is what was responsible for the 63&65 code. Didn't have the 67 as that is for the right side.
Part number #89018365

FLORIDA

Thanks for the clarification. Good info.

sneakelman

No problem. Anytime I can help, I try.

muscl2

First, I have to give a huge THANKS to this forum because you helped me fix my Service ABS and Traction System problem. I had my mechanic pull my wheel off, disconnect the jumper harness, and adjust the pins. Haven't had those messages come on ever since.

On a different note, I thought I fixed my HVAC problem, i.e., passenger side blowing hot air when I turn the AC on, but it's back. I pulled the 18 and 27 fuses, then deleted the HVAC codes (heard the vents reset). The first time I did this, my problem went away, but just a couple of days ago I noticed that the passenger side was blowing hot air again. I pulled the fuses again and deleted the codes, but the codes come right back without my even turning the AC on and I have hot air on that side. A while back I had B0365, but it was only once and has not reappeared. I mention this because I was reading another great thread in which Bill Curlee goes through the GNDs. I'm going to have my mechanic clean the front two GNDs near the wheel wells. Do you think that MAYBE this stands a chance of fixing my actuator problem?

THANKS IN ADVANCE for once again sharing your vast knowledge!!!

FLORIDA

Hey Muscl2,
I agree with the above. I also replaced the right side actuator p/n 89018365 on my 1998. It cost $135.38. It requires the removal of the console and dash. It cleared the codes B0365 and B0367 permanately.
Pulling fuses and/or resetting would only work temporarily. On a temporary basis it is easier to just hold the reset after you check your codes.
HVAC works great now including the passenger side and the auto fan control. I still get one code B0363 left side but seems to operate just fine. If I need to replace the left one I can get to it from under the dash on the left, just have to stand on my head.