99 Suburban A/C Control Problem

[bobdb99]

99 Suburban K1500 5.7 Front and rear A/C. Just put in a new motor so far everything is working great except the A/C. With the front fan control set to off, when I push in the a/c switch the a/c light comes on and the compressor engages. There is cold air blowing out of the rear vents. Now when I select any fan setting on the front fan switch the a/c light goes out and the compressor disengages. The distribution control has no effect on where the air blows out. It always blows from the bottom vents. If I leave the distribution switch set to blow out of the dash vents and quickly move the fan switch to 1-4 there will be air coming out of the dash vents for a second or two. The air then reverts back to the bottom vents. This is totally the opposite of how this should work. I took the control module out of the truck and went to my local dealer to talk to a tech. He had no clue why this was doing this. He said I could try and get a new control module and that might fix the problem. If it doesn't fix it there is $300 spent for nothing. Any ideas?

[j cAT]

Originally Posted by bobdb99

99 Suburban K1500 5.7 Front and rear A/C. Just put in a new motor so far everything is working great except the A/C. With the front fan control set to off, when I push in the a/c switch the a/c light comes on and the compressor engages. There is cold air blowing out of the rear vents. Now when I select any fan setting on the front fan switch the a/c light goes out and the compressor disengages. The distribution control has no effect on where the air blows out. It always blows from the bottom vents. If I leave the distribution switch set to blow out of the dash vents and quickly move the fan switch to 1-4 there will be air coming out of the dash vents for a second or two. The air then reverts back to the bottom vents. This is totally the opposite of how this should work. I took the control module out of the truck and went to my local dealer to talk to a tech. He had no clue why this was doing this. He said I could try and get a new control module and that might fix the problem. If it doesn't fix it there is $300 spent for nothing. Any ideas?

the auto ac control modules fail very often ...especially when this old with the issues you have ..these can be had for around 100.00..............BUT NOT AT THE DEALER !

use the internet to find your part for less...
perhaps a forum member can direct you ...

[777stickman]

Welcome to AF. Need to know what body style your Sub is. Old or New.

Old looks like a '95 and New looks like an '01. Very important info for us to be able to help you.

[j cAT]

Originally Posted by 777stickman

Welcome to AF. Need to know what body style your Sub is. Old or New.

Old looks like a '95 and New looks like an '01. Very important info for us to be able to help you.

with the 5.7L this is old body ...............

this does not matter his controls are screwed up and like the dealer tech said new control module ....for dealer special sale price of 300.oo

only a fool would buy this at the dealer...

[777stickman]

Originally Posted by j cAT

with the 5.7L this is old body ...............

this does not matter his controls are screwed up and like the dealer tech said new control module ....for dealer special sale price of 300.oo

only a fool would buy this at the dealer...

Seems the more dependent/fanatic you get the more of a PITA you get. And there you go with your insults again. What the hell's up with you man??

I personally have never seen any OBS with "auto a/c controls".

Yes his controls are screwed up, but why would that happen after a motor change?? And yes OBS-NBS very much matters due to the electronics involved.

When I ask a poster on this forum a question I hope for an answer from that poster and not some B/S from the dependent/fanatic.

[j cAT]

Originally Posted by 777stickman

Seems the more dependent/fanatic you get the more of a PITA you get. And there you go with your insults again. What the hell's up with you man??

I personally have never seen any OBS with "auto a/c controls".

Yes his controls are screwed up, but why would that happen after a motor change?? And yes OBS-NBS very much matters due to the electronics involved.

When I ask a poster on this forum a question I hope for an answer from that poster and not some B/S from the dependent/fanatic.

like I said only a fool would purchase this at the dealership for 300.00...

like I said this can be had for about 100.oo...as many have found...

he did do not buy this yet because he is not a fool , and was smart enough to come here for guidance...

I have to assume you are with dealerships ....

[bobdb99]

This is the old body stye and it does not have the auto climate control. It would be great for someone to direct to a supplier for this part.

[j cAT]

Originally Posted by bobdb99

This is the old body stye and it does not have the auto climate control. It would be great for someone to direct to a supplier for this part.

with this year Manual a/c vacuum controls the dampers, so make sure you have a good vacuum and check around the engine for good connections and rubber lines for damage etc...

then remove the negative battery terminal for 15min and see if that corrects the problem..

with the part removed pull the numbers off it so it can be checked for part ID>>>...

when you throw the fan switch on /off the dampers do move ,,,but if the controlling device has a leak/defective/low vacuum, this is a reason it does not stay in the vent mode..

[j cAT]

Originally Posted by bobdb99

This is the old body stye and it does not have the auto climate control. It would be great for someone to direct to a supplier for this part.

ACDELCO Part # 1573627 {#1572634, 16177412, 89018395, 89018681}
ACTUATOR,TEMP VLV MODE AND TEMP; w/o RIGHT HAND DRIVE(RHD)

see if this is what you want ...rock auto $40-50.oo ...

[777stickman]

http://www.automotiveforums.com/vbul....php?t=1015672

Read this post from today. Although this is a NBS, with different electronics, it may work for you. It may also screw it up more. My Sub is the same as yours and I would not be afraid to try this.

By the way my OBS Sub has no vacuum controls, only electrical signals.

Try this site. You'll need to e-mail your VIN and what part you need and they'll send you back a part number for your VIN.

http://www.gmpartsdirect.com/

[mishalah]

After reading this thread I'm wondering if my symptoms of weak airflow from the upper front vents might be due to this same controller problem. How would I be able to tell? Should I just try the battery cable "trick"?

[bobdb99]

Thanks for the replies. I will try them when I get home. I'm in Germany for the next week or so.

[bobdb99]

Thanks for all the tips. Home now and tried them all with the same result. Went to the local wrecking yard and picked up a used control module for $48 that fixed the fan and compressor problem. This led to a new discovery. The rear air is significantly cooler than the front. After some research came up with a clogged orifice tube. Swapped it out and refilled system with the same result. I started to poke around under the dash on the pass side and felt alot of heat coming from the heater core. Turns out the heater control valve is not being activated. It appears to be vacuum controlled. I pulled the vacuum lead from the top of a switch that is mounted on the firewall and has two vacumm lines a plumbed to it. One line comes from a pump mounted behind the drivers side headlights and the other goes to a heater control valve. When the pump line is attatched to the heater control valve the valve works as it should. More troubleshooting on this switch and there is no voltage in the electrical lead that goes into this switch no matter what temp is set to. So to temp fix this problem I clamped off the heater hose going into the dash. Now front and rear blow cold air. I need a wiring schematic to trace where this switch gets its voltage from to activate the heater control valve. Sorry this is so long just trying to give as much info as I can.

[j cAT]

the control module was the problem on the compressor/fan issue ..this is why the dealership tech recommended replacement , this very common failure..on you other issues using a meter check all fuses and replace relays in the ac circuits..

having a diagram on this model of these controls would help...I would make new posting with the issues you have now. perhaps a member has this diagram ..

[mishalah]

Very helpful information. Thanks.

j cat; Do you think my low air volume is related to the blend door not functioning properly? Remember I said I have lots of fan noise, but a weak airflow from the dash vents with the a/c on max.