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Hi, I just replaced the A/C compressor. the A/C itself works fine but there are two issues: A/C off while driving there is hot air from the main console. A/C on, the A/C works but the air isn't cold.
At the shops, They told me I have a vacuum issues and I make a workaround to the water heater valve, it should solve it out (close the arm of the valve). I don't have any leaks AFAIK.
Maybe one of the vacuum is disconected? The cruise control works fine .
Thank you.
With the car running and either AC on or HVAC turned totally off, does the arm of that heater valve retract? The heater valve uses vacuum to hold it closed. Also, do you have manual or electronic hvac controls?
In addition to the coolant control valve I would be looking at the blend door in the heater core box. Not sure if yours is cable operated or not, but either way if operating properly it should be able to keep warm air from the core out of the mix.
Ok, I come with some answers:
1 - The water heater valce stays open even the engine is running doesn't matter if A/C is on or off.
2- I replaced all vacuum lines about 3 years ago so I assume there are no leaks or cracks.
3 - attached the lines regarding the cruise control, from the heater/A/C tank and to the plenum.
Yellow - from the heater tank (the ball near the headlight).
Red - to the cruise control servo
Green - to/from the T to the HVAC Control Vacuum Check Valve (passenger side).
other Red - from check valve to the plenum.
Purple - from the firewall to check valve.
Do you have manual climate controls or automatic? With manual controls the heater valve is only closed when the slider is in the full cold position. Doesn't matter whether the A/C is on or not. There is a vacuum switch on the control head in the dash. It may be misadjusted or leaking. On my car, rodents had chewed the vacuum harness inside the dashboard, so I wasn't getting vacuum to a number of actuators.
Do you have manual climate controls or automatic? With manual controls the heater valve is only closed when the slider is in the full cold position. Doesn't matter whether the A/C is on or not. There is a vacuum switch on the control head in the dash. It may be misadjusted or leaking. On my car, rodents had chewed the vacuum harness inside the dashboard, so I wasn't getting vacuum to a number of actuators.
It seems I cannot slide it to HOT at all. in the picture the the maximum slide I can.
Okay, so manual controls. I would definitely look into why the temp slider isn't working. It has a push-pull cable that is connected to a bellcrank on the heater box. The bellcrank is linked to the blend door. You're going to have to get your head under the passenger side dashboard and figure out what's up with the blend door/bellcrank/cable. It should have full travel and theoretically if the blend door closes off the heater core there shouldn't be much heat escaping. A lot of similar climate systems don't use a valve. The core is constant flow and they rely on the blend door. The bellcrank on my car was stuck from corrosion. If that happens people sometimes force the control and damage the cable. Or the blend door can be obstructed, limiting it's movement or something is up with the linkage in the box and the door isn't traveling correctly.
The slider also controls vacuum to the heater valve when in the full cold position. Do you have a vacuum gauge to see if vacuum is present at the valve when the slider is in the cold position? Also use either a vacuum pump or other source to make sure the valve functions when vacuum is applied.
I'll see if there is any other helpful information in my manual when I get to the shop.
Okay, so manual controls. I would definitely look into why the temp slider isn't working. It has a push-pull cable that is connected to a bellcrank on the heater box. The bellcrank is linked to the blend door. You're going to have to get your head under the passenger side dashboard and figure out what's up with the blend door/bellcrank/cable. It should have full travel and theoretically if the blend door closes off the heater core there shouldn't be much heat escaping. A lot of similar climate systems don't use a valve. The core is constant flow and they rely on the blend door. The bellcrank on my car was stuck from corrosion. If that happens people sometimes force the control and damage the cable. Or the blend door can be obstructed, limiting it's movement or something is up with the linkage in the box and the door isn't traveling correctly.
The slider also controls vacuum to the heater valve when in the full cold position. Do you have a vacuum gauge to see if vacuum is present at the valve when the slider is in the cold position? Also use either a vacuum pump or other source to make sure the valve functions when vacuum is applied.
I'll see if there is any other helpful information in my manual when I get to the shop.
Thank you, I don't need the HOT functionality at all, where i live is similar to Florida. Can I just secure the heater valve (close position) and enjoy a cold A/C?
If you don't care about heat you can probably put a zip tie on the valve to hold it shut. However, no coolant circulation will likely eventually cause the heater core to fail. If this job is more than you want to handle you don't want to know what changing the heater core is like. You might be better off bypassing it with a hose between the engine coolant pipes and blowing the core dry.
An update : I secured the "water shut off valve". Now there is no warm air out of the vents. But, air is out everywhere. I took off the little vacuum tube from the check valve. I blew air into it and I could hear the air flowing on its other side. My check valve is on the passenger side not the driver side. On the driver side I have a regular T that connects to the vacuum ball, cruise control and a line goes to the passenger side to the check valve.
What are my next steps?
My 85 vacuum lines are (were) set up the same way, so nothing sounds suspicious there.
Where do you hear air coming from when you blow through the HVAC vacuum tube? Do you hear it in the engine bay, or in the interior of the car? I have my 85 in a million pieces so I can take some pictures and pretty clearly show you how the vacuum lines are routed and where the disconnects are located.
It seems the HAVC check valve works OK. I think I hear the air in the engine bay.
In my car, the main HVAC vacuum line has a 90* elbow in it right near where the vacuum line for the heater valve comes out of the harness.
You could try separating the lines from there to determine if your line is broken closer to the distributor or between there and the firewall. If it is broken near the distributor, simply hook up a new piece of vacuum line to the end going towards the firewall and hook the other end back up to the check valve.
That is what I am working on now in my 85. Trying to dig that broken plastic line out of the engine harness is an exercise in futility.
If you decide to try separating the lines at that elbow, treat it like glass. Those lines break extremely easily. It was definitely a last resort for me.
where should the plalsic line goes? I checked the FSM and took these pics. Also I found on ebay a broken unit but it illustrates the unit vrs the FSM. I haven't took off the HVAC unit yet but should the plastic line be connected to it?
I mentioned before when i blow into the plastic line I hear air in the engine bay, does it a vacuum leak that can cause a leak in the whole vacuum system?
I just checked again the A/C. I checked the lever of : MAX,NORM,VENT and etc. it doesn't matter where the lever is, most the air flow goes through the upper vent on the dashboard.
Air will be directed towards the defrost vent by default without vacuum. Just like the heater valve being open without vacuum, the thought must have been that, in case of a loss of vacuum, defrost and heat are the most important functions of the HVAC system, and all other features just are really just a convenience.
The black vacuum line is where vacuum from the intake enters the hvac controller. From there it is distributed to all the various blend door vacuum actuators based on the selection made on the control head. The gray vacuum line is where vacuum is ported to the heater valve.
If you hear air in the engine bay when blowing through the plastic line behind the intake, you likely have a break or separated connection in that line on the outside of the firewall.
With the car running and either AC on or HVAC turned totally off, does the arm of that heater valve retract? The heater valve uses vacuum to hold it closed. Also, do you have manual or electronic hvac controls?
l currently have the heater core bypassed and no change
1985, A/C issues
