Help please.....a/c blowing out of defrost and floor - no middle vent

Just had the a/c compressor replaced on my 1990 convertible, and I am without air from the center vent - blowing out of the defroster and heat vent on the floor. I think I recall some repair procedure from waaaay back in time that had to do with an adjustment procedure to the cable behind the glove box or some vacuum repair to a door in the dash or connection - can someone please refresh my memory....?

Thanks,

Nic

Maybe the vacuum line to the HVAC is disconnected. No vac, and it defaults to defrost.

Thanks for the reply Harry..

I took your advise and checked the vacuum lines situated around the right rear of the engine compartment and the firewall - they all seem fine (not dry rotted), and fitted properly.

Are they other items that can cause my problem please??

Thanks,

Nic

Nic, It isn't unusual for the vacuum line to come lose or get broken where it connects to the controller. That connection to the controller is inside the car behind the glove box. Have you been doing any work in that area lately? It's common for that vacuum line to get disconnected when working on the ECM or BCM.

THANKS RONNIE ! .....No I have not been doing any repairs on the car other than replacing the a/c compressor (overdue on maintenance etc as well), but I will pull the glove box and have a look-see tomorrow for sure. Thanks for the heads up . It has been more than several years since I have done any work on the cars, and some of these procedures are coming back to my hurting memory. Is this the single line that goes to the BCM that is kind of below the glove box maybe - comes off when replacing the ECM?

Nic

Nic, The vacuum line doesn't connect to the BCM. It connects to a black box with lots of vacuum lines going to it. I called it a controller but I think it is actually a climate control programmer. I looked for a photo of it but I don't have one.

Oh Me...... Memory is really shot I guess. I imagine the area that I should be thinking of is where a cable is also located maybe....directly behind the glove box? I have both early model and '91 shop manuals in the garage so I can go and research for pictures....Thanks again Ronnie,

Nic

Not at home so cannot check but one of the BD values is the commanded HVAC position. If that is right and you have vac at the HVAC programmer then you might have a bad electrical connection or a stuck servo.

Hi Nic,

The vacuum and electrical connections are actually on the bottom of the programmers. No need to remove the glove box, but, you must remove the panel below the glove box area in the footwell. Multi-colored vacuum tubing for the actuators and a black one on an elbow that supplies the vacuum.

HVAC is third from top in right column.

Hi again Folks,,,

I think I may have a big problem..... A friend came over last night and followed the instructions both here and some that Padgett sent me in a PM. We checked for loose hoses and connections. The only way we got the a/c functioning was a vacuum pump was connected to the black vacuum hose at the HVAC Programmer unit below the glove box (the type of hand vacuum pump also used to bleed brakes etc), the pump was pumped approximately 12 times, and the a/c blew out the proper dash vents very cold and "great - big time". Does this mean the I /we will have to replace the vacuum line to the programmer unit from all the way from the engine compartment through the firewall or could the unit be bad or some other part be mal functioning please?

Thanks,

Nic

Did he check for vacuum at the black line coming from the engine compartment? If the programmer works with vacuum applied, it is good. The vacuum connection in the engine compartment is near the firewall, directly behind the throttle body position. The line comes from the vacuum tree on top of the manifold and runs toward the firewall where there is a plastic check valve which is also a tee connection. One line connects to the rear of the tee and goes to the programmer. The line from the side of the tee runs to the vacuum reservoir for the cruise control and also has a tee that splits the line between the vacuum reservoir and the cruise control servo. If any of these lines are deteriorated or disconnected, you won't have enough vacuum to the programmer and the cruise control may not function properly either. It takes 10"-12" Hg vacuum to operate the doors in the climate control and I usually see about double that on the black line coming into the programmer.

Thanks 2seater....I entered a post earlier and apparently it did not post??? I did have some bad lines from the ck valve to the cruise and wanted to replace but was told not applicable - kind of knew better. Soooooo I had some vacuum line on hand and I just replaced the long line from the check valve to the tee, and then the two shorter lines to the cruise control unit and canister - all were deteriorated. Disconnected the hand vacuum pump and refitted the line under the glove box - still no air out of the vents. Has good flow to the defroster and the heater vents. The hard plastic line from the check valve going in to the cowl looks good. Do the check valves go bad?

Also is it possible for the hard plastic line to go defective - if so I have no idea where to buy that type of tubing....how would you run it - would you have to drill a hole in the firewall?

A vacuum gauge would be a great troubleshooting idea...

Anything is possible. If the air flow changes properly when vacuum is applied directly to the inlet of the programmer, then I would move to the next connection in line, the tee under the hood and apply vacuum there. You can also simply check for vacuum with your finger over the connection and the engine running, first at the programmer connection and then keep moving upstream towards the engine. I am not sure if it is even possible, but is the check valve reversed? The tee connection should be on the firewall side. If the system worked normally before the A/C work, what areas were worked on? I would check there. Part of the testing for proper A/C operation would be a temperature probe in the vent outlets. Did it work then?

I agree Harry and I intend on purchasing one...

I did find the problem however.

The black hard plastic line coming off of the check valve was routed flush against the firewall and wrapped around the bottom half (like a half moon) of the wiper motor on the firewall where it protrudes, and then on to the harness that goes thru the firewall. The hose to the firewall appeared ok on first look but I had to find something - on second look the hose at the apex of the half moon wrap around on the protruding wiper motor appeared just a tiny tiny bit thinner. I pulled the hose or better stated tubing away from the wiper motor and it was somehow melted slightly causing the restriction - weird and very hard to see..... I snipped the damaged section out, and joined the two sections with a piece of slightly larger tubing - blowing nicely from the vents now

Thanks Harry, Ronnie, Padgett and 2seater - help is greatly appreciated....

Nic

Opps - forgot....

Any suggestions as to where the hard black plastic tubing can be purchased please?

it's always good to hear solutions to problems - especially when they are cheap and easy!!!:cool:

your thread should be a reminder to all - that sometimes it's not worth overthinking the problem - until the "easy" is ruled out.

example: a few months ago, i thought my Transmission was going out. a quick look at my vacuum hoses and verified with the FSM, showed it was a cracked vac hose.

Do not really need a gauge, just put wetted finger on end of line. If it sticks you have vacuum. If not work backwards until you do.