55trucker Posted May 19, 2018 Report Share Posted May 19, 2018 The source of vacuum for the HVAC & the speed control is the upper plenum, at the rear of the plenum (up against the firewall) you'll find the port for the brake booster vacuum & the MAP sensor, along with the MAP is a small port & a molded tube that supplies the vacuum to the speed control diaphragm & the vacuum tank, a tee fitting behind a one way check valve connects the speed control diaphragm & the vacuum tank. Under the speed control diaphragm is another small port that is the supply for the HVAC in the cabin. You'll see a small rubber 90 degree fitting plugged into the port near the check valve, that's your HVAC supply. That one way check valve is there to prevent vacuum loss in the vacuum tank. When one goes to full throttle nearly all manifold vacuum is lost, the check valve keeps the tank charged so that both the speed control & the HVAC system can function. The tank is Not used continuously, it only comes into play when the engine is at low vacuum. Does your speed control still function? Seeing as you've damaged the tank you'll need to seal off the rubber fitting at the tank to keep vacuum alive, if you pull off the HVAC fitting under the speed control diaphragm with the engine running there should be vacuum at that port. If you also pull off the rubber fitting at the speed control diaphragm there should be vacuum as well, if not then your problem is between the intake manifold & the check valve. You may have a chafed molded line somewhere in that area. *note that a open in the line will cause the engine to run somewhat rough as raw air is being sucked directly into the engine. If there is no issue in the engine bay then you're looking at the solenoid module in the passenger cabin. It is an electric over vacuum device, the HVAC control panel buttons that one presses are the electical side & the actuators in the module are the vacuum side that move the doors in the airbox assembly. The module sits on top of the airbox assembly to the right of centre, one removes the glove box assembly & you can now see the module. primergray 1 Quote Link to comment Share on other sites More sharing options...
89-W-Body-Regal Posted May 20, 2018 Author Report Share Posted May 20, 2018 The source of vacuum for the HVAC & the speed control is the upper plenum, at the rear of the plenum (up against the firewall) you'll find the port for the brake booster vacuum & the MAP sensor, along with the MAP is a small port & a molded tube that supplies the vacuum to the speed control diaphragm & the vacuum tank, a tee fitting behind a one way check valve connects the speed control diaphragm & the vacuum tank. Under the speed control diaphragm is another small port that is the supply for the HVAC in the cabin. You'll see a small rubber 90 degree fitting plugged into the port near the check valve, that's your HVAC supply. That one way check valve is there to prevent vacuum loss in the vacuum tank. When one goes to full throttle nearly all manifold vacuum is lost, the check valve keeps the tank charged so that both the speed control & the HVAC system can function. The tank is Not used continuously, it only comes into play when the engine is at low vacuum. Does your speed control still function? Seeing as you've damaged the tank you'll need to seal off the rubber fitting at the tank to keep vacuum alive, if you pull off the HVAC fitting under the speed control diaphragm with the engine running there should be vacuum at that port. If you also pull off the rubber fitting at the speed control diaphragm there should be vacuum as well, if not then your problem is between the intake manifold & the check valve. You may have a chafed molded line somewhere in that area. *note that a open in the line will cause the engine to run somewhat rough as raw air is being sucked directly into the engine. If there is no issue in the engine bay then you're looking at the solenoid module in the passenger cabin. It is an electric over vacuum device, the HVAC control panel buttons that one presses are the electical side & the actuators in the module are the vacuum side that move the doors in the airbox assembly. The module sits on top of the airbox assembly to the right of centre, one removes the glove box assembly & you can now see the module. I don't understand what you mean by Speed control? Are you referring to the Vehicle Speed Sensor? If you are that is working fine and not receiving any issues with that part. My EGR Vacuum harness is cracked in 3 places but I repaired the tubing until I can find a new harness which is difficult to find because they don't make it. The vacuum line between the map sensor and Canister Purge Solenoid cracked and I did repair that with a thick tubing as well with a connector on one side. I looked and reconnected all vacuum line connected under engine plenum and that isn't cracked and still good. My vacuum line as of now isn't connected to the Cruise Control Vacuum Tank below the front bumper because the inlet port broke off the ball. I am replacing the ball soon and will reconnect the vacuum line. I didn't find any of the vacuum line connected to the tank broken or cracked. It was protected with electrical crimp hose. As for the solenoid module in the passenger cabin below the glove box, are you referring the A/C Heater Panel Mode Actuator? There are plastic vacuum line tubing connected to that actuator and none of the lines are cracked on that. I checked every vacuum line in the engine bay as careful as I could. Like I said only vacuum line that is cracked is the EGR Harness. I repaired that with tubing until I find one. I did have a coil pack issue and just replaced one with the ICM. The car drives fine. So as of now, the only thing I found was the bad vacuum tank. No air comes out of that which so ever even with the engine running at idle and vacuum lines connected to the tank aren't cracked. If the vacuum tank don't fix the no air out of vent issue, should I replace the A/C Heater Panel Mode Actuator? There are only two HVAC Actuators. All relays and fuses are also good. But still no air out of instrument panel vents after pushing each button on the control module. I have an idea what your saying. But what I am wondering is, would replacing a bad cruise control vacuum tank fix the issue of no air coming out of the vents and would it increase the air speed for the windshield defrosters? Right now I am only thinking the HVAC CRUISE CONTROL VACUUM TANK IS THE CAUSE. Quote Link to comment Share on other sites More sharing options...
55trucker Posted May 20, 2018 Report Share Posted May 20, 2018 *Speed control* is the factory term for cruise control, because of the damaged vacuum tank just seal off the open port to the vacuum tank to keep vacuum intact, . You won't get air *out* of the tank as it has no air in it, it is always in a state of vacuum. I don't believe that the tank is the cause of your problem, as I stated earlier the tank only comes into use when the engine as at or near full throttle. The tank is nothing more than a back-up reservoir, but for all to function properly there can be no leaks anywhere. You mentioned in an earlier post that the problem existed before you inadvertently damaged the tank. Look after all of the issues under the hood so all functions as needed, when you go that covered then look at the solenoid module on top of the airbox. Quote Link to comment Share on other sites More sharing options...
89-W-Body-Regal Posted May 20, 2018 Author Report Share Posted May 20, 2018 *Speed control* is the factory term for cruise control, because of the damaged vacuum tank just seal off the open port to the vacuum tank to keep vacuum intact, . You won't get air *out* of the tank as it has no air in it, it is always in a state of vacuum. I don't believe that the tank is the cause of your problem, as I stated earlier the tank only comes into use when the engine as at or near full throttle. The tank is nothing more than a back-up reservoir, but for all to function properly there can be no leaks anywhere. You mentioned in an earlier post that the problem existed before you inadvertently damaged the tank. Look after all of the issues under the hood so all functions as needed, when you go that covered then look at the solenoid module on top of the airbox.[/quote Is there vacuum lines connected to it? I know you stated were it is. But how do you check if it’s bad? Quote Link to comment Share on other sites More sharing options...
89-W-Body-Regal Posted May 20, 2018 Author Report Share Posted May 20, 2018 If this what your talking about? It’s under the glovebox and has rubber vacuum lines on it. It’s the Evap Heater Actuator. If I am correct how do you tell if it’s bad? Quote Link to comment Share on other sites More sharing options...
89-W-Body-Regal Posted May 20, 2018 Author Report Share Posted May 20, 2018 Or this one which is the door actuator? Quote Link to comment Share on other sites More sharing options...
55trucker Posted May 21, 2018 Report Share Posted May 21, 2018 Have a look at the service manual diagrams, hopefully these will clear things up for you..... #18 is object of your desire, it is completely self contained. The solenoids are all in that module. There are 5 different coloured vacuum hoses that connect to that module ....red, blue, orange, yellow & brown, they all drive the 4 different vacuum actuators that move the doors. The diaphragm you took a shot of looks to be either #9 or #1. primergray 1 Quote Link to comment Share on other sites More sharing options...
89-W-Body-Regal Posted May 21, 2018 Author Report Share Posted May 21, 2018 Since all vacuum lines are good... Would this vacuum solenoid fix my issue with getting no air out of the vents? You said this electrical module works every door in every actuator. Quote Link to comment Share on other sites More sharing options...
89-W-Body-Regal Posted May 21, 2018 Author Report Share Posted May 21, 2018 Ok I now disconnected the vacuum solenoid on the passenger side air box. It doesn’t look like it’s working anymore because the door wouldn’t open when I turned on the air. Nothing was still coming out of the vents. So like was said in this forum, I think that could be the issue. Quote Link to comment Share on other sites More sharing options...
55trucker Posted May 22, 2018 Report Share Posted May 22, 2018 Before you condemn it, check the electrical source input to it, make sure that it is receiving voltage & check that the vacuum is at the input side. Quote Link to comment Share on other sites More sharing options...
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