BostonETC97 Posted July 10, 2007 Report Share Posted July 10, 2007 For the past two years nobody could diagnose the reason why my HVAC would occasionally pop from the dash vents to the defroster. The dealer threw vac hoses, new hose fittings, diagnostic tests, etc etc at the car, until they basically said "maybe you should consider replacing the programmer, even though it tests fine." I wasn't in the mood to throw any more money at it yet... Today I finally had enough, grabbed my FSM, and tore the lower dash out. I took the programmer and vac manifold out, disassembled and cleaned the relays and terminals in the vacuum controller, made sure all the hoses held vac and were well seated, and replaced everything. Sounds quick, but took the better part of the afternoon. And it's not much fun contorting yourself to fit under the dash! After taking a drive, I'm thinking I finally have it repaired. The programmer and vacuum connections were not seated in their brackets under the dash properly, causing them to rattle, which I think may have had something to do with their malfunctions. I now have them tightly in place in their brackets. Hopefully that was the fix that was needed. Otherwise I'll be throwing a new programmer/controller and actuator valves at the car next! Hope everybody had a great day! -Scott '97 ETC Link to comment Share on other sites More sharing options...
jackc Posted July 11, 2007 Report Share Posted July 11, 2007 Congratulations! Dash diving is the worst....... Link to comment Share on other sites More sharing options...
BodybyFisher Posted July 11, 2007 Report Share Posted July 11, 2007 For the past two years nobody could diagnose the reason why my HVAC would occasionally pop from the dash vents to the defroster. The dealer threw vac hoses, new hose fittings, diagnostic tests, etc etc at the car, until they basically said "maybe you should consider replacing the programmer, even though it tests fine." I wasn't in the mood to throw any more money at it yet... Today I finally had enough, grabbed my FSM, and tore the lower dash out. I took the programmer and vac manifold out, disassembled and cleaned the relays and terminals in the vacuum controller, made sure all the hoses held vac and were well seated, and replaced everything. Sounds quick, but took the better part of the afternoon. And it's not much fun contorting yourself to fit under the dash! After taking a drive, I'm thinking I finally have it repaired. The programmer and vacuum connections were not seated in their brackets under the dash properly, causing them to rattle, which I think may have had something to do with their malfunctions. I now have them tightly in place in their brackets. Hopefully that was the fix that was needed. Otherwise I'll be throwing a new programmer/controller and actuator valves at the car next! Hope everybody had a great day! -Scott '97 ETC Thanks for reporting your experience. I was under my dash over the weekend and saw the vacuum manifold. I lose the air from my vents when I accelerate up a hill laboring the engine. What can you tell me about the vacuum manifold can you disassemble it? Is it possible for it to leak vacuum? Thanks Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
BostonETC97 Posted July 11, 2007 Author Report Share Posted July 11, 2007 The manifold itself (with the 4 colored tubes exiting to the actuators) is separate from the actual HVAC programmer (silver colored computer-box.) They sit next to each other in a plastic bracket, and are connected by a cable. I unplugged the programmer (2 large wire harnesses with easy-disconnect clips, one cable to the "vacuum" controller), and removed it from the car. The vacuum tubes don't easily disconnect, so I left them intact, but removed the manifold from the bracket and laid it out on the passenger-side floor. I knew I wasn't loosing any vacuum, so the problem could only be a bad programmer or vacuum control module. I took a can of canned air, and blew all the dust/debris out both parts, paying special attention to the "relays" on the vacuum module. You can actually feel them clicking if you hold the vac-controller (manifold) in your hand while you cycle through the different modes (floor-dash-defrost.) I also pried the cover off, and "cleaned" out all the junk i could. After cleaning all the contacts, plugs, connectors, etc., I re-installed both the programmer and the vacuum controller, making sure they snapped into place in their bracket. I then re-connected all the cables. My theory is that my vac module and controller were not properly seated, and were rattling around under the dash. Now that they have been re-seated, and all their connections cleaned, they seem to be behaving. I didn't really notice any relation to driving up/down hills, throttle position, or engine load when my a/c would start blowing through the defroster. If I played with the 'mode' switch a few times, it would usually return to the vents. Sometimes it wouldn't act up at all, other times I could barely get ANY air out the vents. Your situation sounds much more like a vacuum leak. I'd take a look at all the vac lines, especially the ones under the hood. The rubber hose tends to dry out, and form hairline cracks. All my hoses on the interior are in great shape, but under the hood their age is starting to show. The a/c vent issue is definitely one of those highly annoying problems that seems nearly impossible to fix. Since it can be several systems (electrical, vac, mechanical actuators), you really need to isolate each system and figure out what works and what malfunctions. I suppose what I found most annoying was that the 'floor' or 'defrost' positions were never affected, ONLY the vents for the a/c. I could have really care less if hot air blows between the floor and dash randomly in the winter, but on a hot day, I NEED the dash vents to work! I'll report back over the next few days about the results. Tonight I drove for about an hour, and everything worked great for a welcome change! Hopefully it's fixed! Link to comment Share on other sites More sharing options...
BodybyFisher Posted July 11, 2007 Report Share Posted July 11, 2007 The manifold itself (with the 4 colored tubes exiting to the actuators) is separate from the actual HVAC programmer (silver colored computer-box.) They sit next to each other in a plastic bracket, and are connected by a cable. I unplugged the programmer (2 large wire harnesses with easy-disconnect clips, one cable to the "vacuum" controller), and removed it from the car. The vacuum tubes don't easily disconnect, so I left them intact, but removed the manifold from the bracket and laid it out on the passenger-side floor. I knew I wasn't loosing any vacuum, so the problem could only be a bad programmer or vacuum control module. I took a can of canned air, and blew all the dust/debris out both parts, paying special attention to the "relays" on the vacuum module. You can actually feel them clicking if you hold the vac-controller (manifold) in your hand while you cycle through the different modes (floor-dash-defrost.) I also pried the cover off, and "cleaned" out all the junk i could. After cleaning all the contacts, plugs, connectors, etc., I re-installed both the programmer and the vacuum controller, making sure they snapped into place in their bracket. I then re-connected all the cables. My theory is that my vac module and controller were not properly seated, and were rattling around under the dash. Now that they have been re-seated, and all their connections cleaned, they seem to be behaving. I didn't really notice any relation to driving up/down hills, throttle position, or engine load when my a/c would start blowing through the defroster. If I played with the 'mode' switch a few times, it would usually return to the vents. Sometimes it wouldn't act up at all, other times I could barely get ANY air out the vents. Your situation sounds much more like a vacuum leak. I'd take a look at all the vac lines, especially the ones under the hood. The rubber hose tends to dry out, and form hairline cracks. All my hoses on the interior are in great shape, but under the hood their age is starting to show. The a/c vent issue is definitely one of those highly annoying problems that seems nearly impossible to fix. Since it can be several systems (electrical, vac, mechanical actuators), you really need to isolate each system and figure out what works and what malfunctions. I suppose what I found most annoying was that the 'floor' or 'defrost' positions were never affected, ONLY the vents for the a/c. I could have really care less if hot air blows between the floor and dash randomly in the winter, but on a hot day, I NEED the dash vents to work! I'll report back over the next few days about the results. Tonight I drove for about an hour, and everything worked great for a welcome change! Hopefully it's fixed! Thanks for that info Scott, that will be helpful this weekend. I have already replace all hoses and tubing and fittings under my hood. So I am looking forward to digging in under the dash... Thanks, Mike Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
BostonETC97 Posted July 12, 2007 Author Report Share Posted July 12, 2007 2nd day since my 'repair', and I'm happy to report the vents are still blowing from the dash without any hiccups! My other observation is that my a/c is now ICE cold. If I have it set on auto-65-low, I'm now practically frozen out of my car within a few minutes. Previously, the air was just coolish at best, even set at 60. I really think some dirty or loose electrical contacts on the programmer were causing havoc in the HVAC system. I'll post back in a week or so, and we'll see if this repair sticks! -Scott Link to comment Share on other sites More sharing options...
Bruce Nunnally Posted July 12, 2007 Report Share Posted July 12, 2007 Good news so far then. I hope it stays fixed. Bruce 2023 Cadillac CT4-V Blackwing Follow me on: Twitter Instagram Youtube Link to comment Share on other sites More sharing options...
Acassin Posted October 8, 2007 Report Share Posted October 8, 2007 Scott, I had a similar problem with my hvac and spent the money to have the programmer replaced only to develop an intermitent interruption to the ac coming out the vents. It would blow fine out the defroster and floor vents when I set it to defrost but otherwise would only blow out the vent intermitently. When I took it back to the shop that did the original repair the mechanic opened the underside of the dash and said the hoses had becomed pinched. That repair worked for a couple weeks but then the symptoms returned. I opened the underside of the dash myself this afternoon and began to grope around not really knowing what I was doing and the ac starting blowing out the vents again. When I put the panel back in place the airflow from the vents stopped. I reopened it and tried to reposistion the hoses so they could not be pinched and now it has worked for most of the afternoon. It was extrodarnarily tight under there and I can't fathom that cadillac would design these hoses so they simply lay up against the bottom of the airmixture box. I am also worried that the programmer may not have been installed correctly and may be rattling around causing the intermitent problems that occurred previous. Any thoughts or suggestions would be appreciated. Link to comment Share on other sites More sharing options...
Texas Jim Posted October 8, 2007 Report Share Posted October 8, 2007 Thanks for reporting your experience. I was under my dash over the weekend and saw the vacuum manifold. I lose the air from my vents when I accelerate up a hill laboring the engine. What can you tell me about the vacuum manifold can you disassemble it? Is it possible for it to leak vacuum? Thanks Mike, I have had 3 Chevy Astro Vans, that at about 120,000 miles, did exactly that. Going up a long hill, kinda straining, but not enough to make it downshift... it would divert ALL the cool air to the defroster vents. When I level out and ease up on the gas... air would come back to the dash vents. Turned out to be a bad hose from the engine to the manifold under the dash. The dash on the Astro Van is almost impossible to take loose and there is NO clearence to get your hands and arms up in there to work on it. It is MUCH more crowded up under the dash than the Cadillac. I tried to fix the first one. But after an hour under the dash... with my arms scratched up, looking like you had taken a big wood rasp to them...I took it to the Chevy dealer. 45 minutes and 90 bucks later ... it worked great. Took a week to heal all the scratches on my arms. The next two.... I just dropped 'em off at the dealer to fix. Looks like you are on the right track to get it fixed. Link to comment Share on other sites More sharing options...
BodybyFisher Posted October 8, 2007 Report Share Posted October 8, 2007 For the past two years nobody could diagnose the reason why my HVAC would occasionally pop from the dash vents to the defroster. The dealer threw vac hoses, new hose fittings, diagnostic tests, etc etc at the car, until they basically said "maybe you should consider replacing the programmer, even though it tests fine." I wasn't in the mood to throw any more money at it yet... Today I finally had enough, grabbed my FSM, and tore the lower dash out. I took the programmer and vac manifold out, disassembled and cleaned the relays and terminals in the vacuum controller, made sure all the hoses held vac and were well seated, and replaced everything. Sounds quick, but took the better part of the afternoon. And it's not much fun contorting yourself to fit under the dash! After taking a drive, I'm thinking I finally have it repaired. The programmer and vacuum connections were not seated in their brackets under the dash properly, causing them to rattle, which I think may have had something to do with their malfunctions. I now have them tightly in place in their brackets. Hopefully that was the fix that was needed. Otherwise I'll be throwing a new programmer/controller and actuator valves at the car next! Hope everybody had a great day! -Scott '97 ETC Thanks Scott, you were right. I pulled the vacuum hose block off of the programmer and re-set all of the hoses and mine stopped drifting from vents to defroster also on laboring acceleration. I was so happy, as I had replaced all the vacuum hoses down to the black vacuum tank and the check valve... Easy fix, glad you found the problem. Here is the thread for my job http://caddyinfo.ipbhost.com/index.php?sho...967&hl=1340 Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
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