Mr. Anderson Posted March 14, 2016 Share Posted March 14, 2016 Hi all! Haven't posted in some time due to trying to finish my music degree, but I still have been working on my 91 little by little and have finished everything except for paint and the no air out of the dash vents issue. Well today, I decided to set everything aside and go after the issue. In short, I have the bottom of the dash removed so I could look up at the clip attached to the blend doors thinking that it may be broken. However, it appears that it is still in one piece, but I still have no idea why I only get air out the defroster and floor vents. In diagnostics, the programmer checks out to be doing its job as the temperature arm moves properly and it appears to be commanding the doors to work, yet nothing changes. Also, the A/C works properly and has been converted to 134a. Am I now dealing with a vacuum issue or do I have a faulty valve? Link to comment Share on other sites More sharing options...
2seater Posted March 14, 2016 Share Posted March 14, 2016 It sounds like a possible vacuum issue since you have eliminated two other culprits. The best way to verify vacuum is getting to the programmer is to pull the black line from the bottom of the programmer. That particular line has a 90* elbow on the end where it slips onto the programmer tube cluster. You should have full manifold vacuum in that line. If vacuum is low or non-existent, the other end of the black tube connects to a tee near the firewall in the engine compartment. Start there. Link to comment Share on other sites More sharing options...
DAVES89 Posted March 14, 2016 Share Posted March 14, 2016 It could be the evaporator that is all clogged up and not allowing the air to pass through. What I did was a liitle different then Barney's recomendations. I removed the blower control module located on the top of the fire wall. I then removed the heater/A/C fan. I laid a small light [used a low wattage night light plugged into an extension cord] in the opening where the fan is, and then sprayed the evaporator fins down with carb cleaner. I then followed with water using a sprayer nozzle on a hose, followed by compressed air. My thoughts were the carb cleaner loosened everything up, the water neutralized the carb cleaner and rinsed everything off, and the air dried everything up so I could repeat with the carb cleaner. I did 3 cycles of that and everything cleaned up well and the air flow was greatly improved. 1 Link to comment Share on other sites More sharing options...
Mr. Anderson Posted March 15, 2016 Author Share Posted March 15, 2016 If the evaporator were clogged, then wouldn't that mean that I would get no air flow through any vent, regardless of the position of the blend doors? I'm sure that it could use a good cleaning out, but I have pretty good flow through the defroster and floor vents. I also know that the blower itself is not an issue because it works at all of the different speeds, and the AUTO feature works as well. Link to comment Share on other sites More sharing options...
padgett Posted March 15, 2016 Share Posted March 15, 2016 Vacuum line gets knocked off the tee by the cruise control a lot. Link to comment Share on other sites More sharing options...
Mr. Anderson Posted March 15, 2016 Author Share Posted March 15, 2016 Just got back and verified that I have a pretty good vacuum on the black line at the programmer. Also double checked the vacuum lines in the engine compartment and they are all in place and look good. Could I have a bad solenoid in the programmer? Link to comment Share on other sites More sharing options...
2seater Posted March 16, 2016 Share Posted March 16, 2016 It's possible to have a bad solenoid. I think if you go through the diagnostic tree in the FSM, it concludes the programmer is bad if the air flow doesn't match the commands that are indicated. I don't have access to my notes right now but if memory serves, the blue line controls the upper valve for the defrost, the red and yellow direct air high and low and the orange is for the outside/inside air control. If there is no vacuum to the red/yellow air valve the default is an approx. even split between upper and lower. You can activate the actual air valves by applying vacuum directly to the lines from the programmer by disconnecting the vacuum connector assembly on the bottom of the programmer which is held in place with a small nut on a stud in the center of the connector. A hand vacuum pump is the easiest way to do so, but you could use the engine vacuum line (black) applied against the individual openings for the various lines in a pinch (engine running). If the lower area is still open as shown in the photos you should be able to see them move or get a change in the airflow. Link to comment Share on other sites More sharing options...
padgett Posted March 16, 2016 Share Posted March 16, 2016 (edited) I have also seen vacuum lines fall off and a misaligned servoactuator jam in the duct (usually opens suddenly with a bang). Can just reach if run hand up between gas pedal and console near top of dash. A Mighty-Vac is a handy thing to have. Edited March 16, 2016 by padgett (see edit history) Link to comment Share on other sites More sharing options...
chipcross Posted March 17, 2016 Share Posted March 17, 2016 Since we are on the topic of air flow from the vents, I thought I would ask the forum a similar question. When I start my '90, the air flows out of the heater and defroster vents only. Then, about ten minutes later, the cabin vents open up and flow normally. Anyone had a similar situation? (Summer is coming and I would like to point my mechanic in the right direction!) Link to comment Share on other sites More sharing options...
Mr. Anderson Posted March 17, 2016 Author Share Posted March 17, 2016 Since we are on the topic of air flow from the vents, I thought I would ask the forum a similar question. When I start my '90, the air flows out of the heater and defroster vents only. Then, about ten minutes later, the cabin vents open up and flow normally. Anyone had a similar situation? (Summer is coming and I would like to point my mechanic in the right direction!) I believe what you are experiencing is the A/C system purge. This is normal for the car. When you first start up the car, the system will empty out any air it has in it, and shortly after, the programmer/BCM will command normal airflow. Link to comment Share on other sites More sharing options...
Mr. Anderson Posted March 17, 2016 Author Share Posted March 17, 2016 An update: I disconnected the vacuum lines from the bottom of the programmer and individually connected the engine vacuum line (black) to each of the color coded lines. When I connected to each individual one, the air was directed out of the appropriate vents (even out of the front vents when connected to blue). Would this result mean that I have a faulty programmer? Link to comment Share on other sites More sharing options...
2seater Posted March 18, 2016 Share Posted March 18, 2016 It sounds like a faulty programmer to me. Since you can get the air flow to change manually, the business end of the system appears to be functioning properly and you have enough vacuum supply to move the actuators. It is possible you have a stuck solenoid in the programmer but I don't know of a good way to free it up. You could try tapping on the bottom of the programmer in a vertical direction because I did discover the valves must be in the vertical position to have gravity help seal the valve when closed. A single vacuum feed tube connects internally to a check valve assembly with multiple outlets that connect to the individual solenoids. If a solenoid is stuck in between, it is possible to leak vacuum out the exhaust port weakening the vacuum available to the others since they have a common feed manifold. A couple of years ago I did a dissection of a programmer and modified one to operate external aftermarket solenoids, which works perfectly, but a replacement programmer is likely an easier option. I am making the assumption you do not have a hand vacuum pump to pull a vacuum on the inlet where the black tube connects which should hold reasonable vacuum, or, run the engine with all the tubes connected, shut off the climate control and the engine, then pull the black line again. It should have held some vacuum and you will hear it hiss when disconnected. If not, there is a solenoid(s) venting to atmosphere. In addition to the AC purge as mentioned, when heat is required, the fan will not spool up until there is some heat in the engine to prevent instantly fogging the windshield or cause a cold draft. This is also normal. Link to comment Share on other sites More sharing options...
Mr. Anderson Posted May 10, 2016 Author Share Posted May 10, 2016 Let me wrap this thread up after a long break. After finishing a very long semester at school, I bought a good used programmer from Jim Finn. I am pleased to say that the programmer was the problem all along, and now I have air coming out of the correct vents! Thanks to everyone for all their help with this issue! Link to comment Share on other sites More sharing options...
2seater Posted May 11, 2016 Share Posted May 11, 2016 Sounds good, thanks for letting us know. Link to comment Share on other sites More sharing options...
padgett Posted May 11, 2016 Share Posted May 11, 2016 And now if it fails again you have spare parts. 1 Link to comment Share on other sites More sharing options...
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