HVAC issue

I'm having a problem with my heating and ac. When I set the heater to the fresh air floor setting I get heat out of the defrost vents. I assumed vacuum leak but hooked a smoke machine up and saw no leak anywhere.

If not a cac leak what would cause that, hopefully not blend door issue?

Sounds like the all too common (cracked, broken, loose...) vac line tubing at the firewall where the coolant hoses and AC hoses connect has a small leak. If not check the vac motor on the bottom of the dash stuff on the passenger side near the door. What year is it?

I had problems with that hose in the past and currently have it taped up. I thought for sure that would be the problem too but using smoke I had no sign of a leak there. Maybe I will just finally run a new hose direct from the control snd get rid of that plastic line.

I thought maybe a leak at the vacuum ball behind the bumper too and again nothing. My cruise control works just fine if thst means anything vacuum wise.

97.

Tape will not do the job on those small vac lines. Just a tiny hole or seal leak on the hose or tubing near the firewall is too much for the AC controls. I had a defective rubber hose, brand new on that line that was slightly out of round on the inside and every time I pressed the gas peddle, the engine vacuum dropped enough for that leak to make the damper doors start flipping locations. That leak was hard to find. Found it one day when I had the hood up and the engine was just cut off, and I could hear the leak. That was how I found it.

Still having the issue. I patched in a piece of hose by the firewall confirmed no leak with a smoke machine.

The ac recirculation settings work as they should but there's no floor only setting. Anything that would cause just the freesh air settings to send air through the defrost vents also only the ones above the dash vents and not the wiendshield defrost vents?

I just want fooor heat not heat blowing out of my dash vents right at me ha.

iwannadie said:

Anything that would cause just the freesh air settings to send air through the defrost vents also only the ones above the dash vents and not the wiendshield defrost vents?

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Yes, a vacuum leak as Ecomike said. So where did you look for smoke. did you look in the cab, in the engine bay. at the vac reservoir. The HVAC system is designed to default to defrost in most if not all vehicles before 2000 or so. Some newer models are still using the same system.

The vacuum lines don't just end in the engine bay. They also come in to the cab, behind the heater controls and are distributed by a "manifold" inside the dash that control all the directional doors. If there is a leak anywhere in the system (except in the engine side vac lines) it WILL default to the defrost.

Re-do the smoke test. Shine around with an LED flashlight (it shows up better) from the vac source line off the intake manifold, all the way to the vac reservoir. If you find any sketchy vac lines...replace...not just repair... the entire line. Bulk vac line is cheap. Also, take out the HVAC controls of the dash, check to see that a line or fitting hasn't come off the plastic manifold in the dash area, check for smoke or physical evidence of a leak. Like said above, a crack, a split, a rub could be enough to lose vacuum to make your HVAC act up.

I've never had a car or truck that had the same issue that wasn't a vacuum leak and I've been around for awhile...my first car was a brand new 1968 Ford Fairlane and it had the same type of system.

iwannadie said:

Still having the issue. I patched in a piece of hose by the firewall confirmed no leak with a smoke machine.

The ac recirculation settings work as they should but there's no floor only setting. Anything that would cause just the freesh air settings to send air through the defrost vents also only the ones above the dash vents and not the wiendshield defrost vents?

I just want fooor heat not heat blowing out of my dash vents right at me ha.

Click to expand...

Where exactly is the air coming out, and on what control settings? Kinda sounds like you might have a vent control valve or linkage issue, but can not make out clearly what you are saying is happening. I have no faith in smoke tests as the engine fan blows air around too much, and the engine needs to be running to get vacuum. I found a super tiny leak once caused by defective guts, not round on the inside, brand new rubber vac hose I had used to mend the busted vac tubing. I found it by standing at and listening for a sucking sound at the HVAC hose area under the hood as someone else shut the engine off. No smoke machine would have found that tiny leak IMHO.

The vac reservoir and under the battery are the usual suspects. There are check valves to preserve the vacuum when the engine is off. Depending on where you inject the smoke, you may not get past the CVs.

All my hvac settings seem to work as usual except the fresh air floor only setting. When on that setting air comes out of the floor vents but also out of the two defrost vents about the dash hvac vents on the far sides, both passenger and driver side(nothing out of the center windshield defrost dash vent). In the past on the floor only setting air only comes out of the floor vents.

Go here and download a manual.

http://cruiser54.com/?page_id=365

Here's some images that you can study:


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