No control over HVAC Vents

[okaussie]

It is me again. Now that the temps are below 100 here I went to check the other vent settings on the HVAC to make sure they all still work. And what do you know, they don't.

I have A/C in all positions and only in the dash vents. I also have temperature control and blower speed.

No defrost, heat plus defrost, and foot. Don't hear the vacuum kick in to change the actuators. I have minimal vacuum on the black line to the mutli connector behind the dash. I did not feel any vacuum any where else on that connector, being disconnected and switching the Control on the dash..
I do hear a kind of a moan when I go from Max A/C to OFF. nothing from OFF to Max A/C. The A/C compressor is running like it is suppose to and the temperature control works like it is suppose to.

This all seem to have started since I got my truck back from the shop after the transmission bolt issue.

I did check the vacuum line coming off the engine to the one way valve. It is connected. checked for vacuum there, good. Checked on the other two sides of the one way valve, they too are good..

Replaced the HVAC Head on the dash last year due to a bad transfer case switch with the tranny fluid issue. Never had a problem like this until now.

Any ideas???

I am working through the weekend til Monday and will do some more checking then.

BTW mine is a 2002.

TIA

Bill

[HenryJ]

Does your 4x4 work? Are the three line to the t-case switch attached? Check the lines behind the brake booster for dry rot. Also make sure the line to the vacuum reservoir in the fender is attached.

[okaussie]

The line to the reservoir is attached. Did not see any dry rot. Will check the the 4x4.

Where does the vacuum for the dash controls enter the cab??

I am wondering if they missed hooking up that vacuum hose when they put the engine back in. I will also check the cruise control to see that it works.

When I put it in another position than Max Air I hear nothing regarding vacuum. The engine sounds like no vacuum leaks there,.

Could they have kinked a tube somewhere???

Bill

[HenryJ]

Do you have good vacuum in the line to the reservoir?
Sorry , I don't remember where the vacuum supply line for the HVAC enters the cabin. You'll have to follow lines to find it.
They could have missed a line, I suppose anything is possible.

[okaussie]

Last year I replaced the line from the intake manifold to the one way valve. Then I replaced the line from it to the reservoir. when I unkooked that line, I could hear vacuum. I replaced the line from the one way valve to the connector below the brake booster. Pulled it off too and had vacuum. I think i have a small amount of vacuum on the black line on the multi connector behind the glovebox, but I don't know. Very minimal at best.

When I switch from Max A/C to any of the other settings, I hear nothing and feel nothing change. All the air flow still comes out of the front vents.

If switching from OFF to MAX A/C only turns on the dash vents by default without vacuum.

I would think that there is no vacuum getting to the control. If that is not the case and vacuum is applied to to that function, then it looks like the control is defective and not allowing any vacuum that is applied to the control to go anywhere else in the control except to MAX A/C. Could had another bad control...

Due to the engine and tranny problems I spoke of on other posts, I tend to think I have a kink or no connection to vacuum.

I did have a smell coming from the engine when I got it back and found they had left some insulation too close to the exhaust manifold on the passenger's side causing it to smoke. Also found a vent tube misplaced that was supposed to be mounted on the radiator shroud, and a nut missing on the air intake housing.

That is what I base my assumption on either a kink in the vacuum tubing to the control or it not even being attached.

Monday I will have to look into it more and see where all the tubing goes.

BTW the Cruise Control works. I tried it tonight going to work and it works just fine.

Bill

[SleeperSS]

The line that enters the cabin is a hard flexible plastic. If memory serves, it enters in amongst a bunch of wires by the steering column.

[okaussie]

So it goes in around where the vacuum booster is for the brakes?? I think mine has some kind of "T" fitting down there.

I thought I would get a vacuum gauge and check the vacuum on the multi connector behind the glove box. I don't here anything there when I disconnect it and play with the control on the dash and don't here anything move when it is connected.

I still think I have something not connected when the engine was put back in.

I know that it has good vacuum from the intake manifold to the one way valve and through the valve to the fender reservoir and off the remaining port off the one way valve. Maybe everything is hooked up properly but the one way valve is decreasing the vacuum enough to keep the HVAC from working right.

I did check the cruise control and it works just fine. Have yet to check the 4x4 yet. Will do that tomorrow.

I did bypass the one way valve and go directly to the intake manifold. I saw and heard no change behind the dash. maybe my problem is between the one way valve and the HVAC Control. If this is where the vacuum comes from the engine.

Will take a look tomorrow when I get off from work...

Thanks,,,

Bill

[okaussie]

I think I found the problem. The one way valve seems to decrease the vacuum so much that nothing downstream from it works correctly. Suspect it as the problem. I took it out of the line. blew out all of the "T" connectors and the HVAC Control started working. Put it back in line and now I think it is flaky.

Called NAPA to get one. They told me the only way was to order it online. Called right down the street to Advance Auto Parts and they would have to order it but they could get it.

Will be in tomorrow. Will pick it up after work in the morning.

I also have been having trouble with the 4x4 so this may fix everything..

More news tomorrow..

Bill

[okaussie]

Also, think I have a problem with the vacuum reservoir in the fender. When I accelerate and the vacuum drops in the engine, the actuators on the HVAC quit, thereby opening doors that are closed when there is enough vacuum. When the vacuum comes back in the engine the actuators come back on and everything goes back to normal.

If I understand it correctly, if the reservoir is working correctly, the above problem doesn't happen since there would be the necessary surplus vacuum to be used until the engine vacuum comes back.

After I replace the one way valve in the morning, I will check this problem out.

Bill

[HenryJ]

Could that check valve be in the line backward?

[okaussie]

Don't think so. One port is considerably larger than the other two. The large one goes straight to the intake manifold and the two small ones on the opposite end are the ones that goes to the reservoir and to the 4x4 and HVAC Control.

I did try to reverse it and did not work do the size of the one port..

I will be picking up the new one in a little bit.

I will let you all know what happens,,

Bill

[okaussie]

Replaced the valve and hose to the intake manifold. HVAC works fine now, except. When accelerating the vacuum drops and it appears no reserve vacuum to keep the HVAC controls in place until the vacuum from the engine picks up again.

What is the best way to check the reservoir?? I think it must have leak there.

I am thinking using a vacuum pump with gauge and apply vacuum to the reservoir and watch the gauge to see if it changes. If it loses vacuum that should tell me,right???

Bill

[HenryJ]

...
I am thinking using a vacuum pump with gauge and apply vacuum to the reservoir and watch the gauge to see if it changes. If it loses vacuum that should tell me,right?

That is right.

[okaussie]

Have you ever seen one of those reservoirs go bad???

Looks like a bear to replace since it is under the ABS module..

Bill

[HenryJ]

I have seen one cracked. It was involved in an accident though.

[okaussie]

If it is not that I kind of lost. Thought I would go buy Harbor Freight today and get the tool.

How about making up a new canister with PVC pipe, two caps and a nipple??

Bill

[okaussie]

One thing I haven't tried is to cap off the leg of the valve that goes to the 4x4. Maybe that part of it is the problem.

Just something else to check

[okaussie]

I am getting further along with the troubleshooting. This morning I capped off the line that I think goes to the transfer case switch and test drove my truck. No loss of vacuum as evidence by the fresh air / recirculating door stayed in the same position during acceleration. This is with the vacuum reservoir connected.

I am looking at the possibility of the hose from the one way valve to the transfer case switch. This test was done in 2HI. Which is where all the other tests were done.

It is raining here today so I may not be able to go any further for a few days.

Looks like I will be replacing vacuum hoses.

The transfer case got replaced last year when the seal in the transfer case went bad and sucked all the tranny fluid into it. screwed the switch. So I know it has a new switch and this problem occurred prior to the switch being replaced. With the transfer case in 2Hi, there should be no vacuum coming out of it to the 4WD actuator under the battery. That is what I am thinking and why I think the hose has a problem between the one way valve and the transfer case switch..

Any other thoughts???

Bill