Need Help w Heater Blower Failure

Nocturne13

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Jun 14, 2020
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In the last few days I noticed a fine mist occasionally come out of the vents as I drove with the air on. I am disabled and will die in SC wo air! LOL It made me worry. The air stopped altogether a couple of days ago. Absolutely nothing coming out at vents, windshield or floor. The fuse is OK I think - and I can hear the blower it seems. You can hear as you change blower speed (sounds normal for instance when you set it to "high") but it has no actual effect on output whatsoever. No moving air despite the sound of a working blower. I have no idea if it is motor, heater valve, resistor. Then symptoms changed dramatically. I tried the car with just the keys turned to "ignition on" as I was trying to get some clues. I actually felt air blowing out at the windshield. Only at the windshield no matter how I set the air controls. I started the car to verify the change under running conditions - suddenly air came out of the vents like it was supposed to. All fan speeds responded with the right amount of air. A few minutes after going down the road the air completely quit blowing again. I was leaning toward a new resistor and blower after reading much of the night but not sure, but now I am wondering with the mist I have been seeing in the car and the fan suddenly working maybe the heater control valve (I read that can cause a coolant leak inside)? Could it even cause this behavior with the AC / blower?

I am honestly in over my head but can't afford mechanic. Could anyone tell me what this sounds like? I need to identify the part(s) I actually need and try to do the job myself. I can barely afford food and my doctors, mechanics are a luxury I just can't afford! Thank you for any help you can provide. - Wes
 
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Nocturne13

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Likely a vacuum problem, the doors that direct air are vacuum operated, start under the hood along the top of the firewall from the tree.

I am very grateful for the reply, I really need some guidance. Thank you. I went out this am to try to check vacuum lines. I only found one in the area I think it could be - it runs from the driver side fender well across the firewall to the area where the heater core hoses and AC stuff is in front of the passenger seat and then ducks into the cabin. It appears to be fine - it is a very small line but is well protected and it seems solidly connected at the source. It isn't too close to the engine and I don't see any breaks or damage.

Also, I wonder if it can be a vacuum issue. I have been trying to research this with little to no luck - mostly just getting more confused. But I found a video online of a guy fixing a HVAC blower issue on his 1998 Mustang (I figure it must be similar to my 94). His issue was no matter what his controls were set on - the air blew out at the windshield. He traced down vacuum lines under the hood like you suggested, and found a broken vacuum line. He used heat shrink to repair it and instantly fixed his blower problems - air came out in right places. So if it was a vacuum related issue, I should be getting air out at the windshield and no where else when the fan is on, right? Because that seems to be the "default" setting. So I don't "think" it could be vacuum because I know sitting in the driveway there are times when air won't blow out anywhere, and also because it is a strangely intermittent problem. (I was thinking a vacuum line problem would mean that it wasn't going to work again until the leak was fixed?)

It is confounding because one occasional symptom kind of points to it.* This am I tried the blower again. It worked normally for a few seconds at the vent position with ignition on, then it did change and would only come out at the windshield.* Then I cranked the car and suddenly it worked like it is supposed to again - windshield, vent, floor and mix all worked flawlessly. But if I try to drive to town it will just quit completely within minutes and burn me alive under the Carolina sun. It won't blow out anywhere - even the windshield. (At least I don't think it does, my brain is almost fried now. I am going to try to verify this.) It almost seems as if it usually starts out OK and then as something possibly heats up it fails?
 

Nocturne13

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If I was to try and replace the vacuum line to rule it out - is it hard to get to inside the dash? Is that a complete dash removal? I can't even find it entering the car from the passenger floorboard. Thanks.
 

General karthief

wonder how much it would cost to ship you a pair
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With the engine running and the ac on, blower on high pull the vacuum line off of tree on the firewall and check if it moves to the defrost mode.
 

2000xp8

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I don't know how much different a 94 is verse a fox, but I've caused my own issues working on the car under the passenger side glove compartment. There is a bunch of colored vacuum lines at a splitter that come undone easily.
 

Nocturne13

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With the engine running and the ac on, blower on high pull the vacuum line off of tree on the firewall and check if it moves to the defrost mode.

OK, this is what I got but I am not certain what it means. Got car running AC and blower on high blowing out dash vents. I pulled off the HVAC vacuum line from the tree and checked airflow. At first I was kind of shocked - air was still pumping out strong at vents. But then I switched it to defrost and back - the air did go to defrost with the vac line removed but it would not come back to the vents when I switched it back. Same thing if I tried turning it off - I could not get air to come out of vents again without reconnecting the vacuum line. So I guess the vents kept working bc they were already in that position??? I thought with no vacuum they would immediately revert to default defrost mode. Could you help me interpret what this means? My brain feels like the one Igor brought back in Young Frankenstein - the one from "Abbie Normal." Does this rule anything in or out? I am thinking the blower and resistor must be good, but am not sure what is the problem. BTW, just judging by pressure on my finger I think the vacuum at the tree is really strong - more so than I expected. Thanks!!

I don't know how much different a 94 is verse a fox, but I've caused my own issues working on the car under the passenger side glove compartment. There is a bunch of colored vacuum lines at a splitter that come undone easily.

I am not sure of differences either - from pics online I hoped to just replace the vacuum line under hood from vacuum tree to HVAC check valve to test it but I don't have a check valve under the hood - line just goes straight through firewall it seems. Only connection under the hood is at the tree. So IDK if I can replace it. My back is held together with plates and pins and I ain't small so crawling in the mustang floorboard is a problem for me these days. I can see the blower motor housing and the resistor - those I could reach if needed. And those are the only two things that I *think* are ruled out now. I couldn't even find the vacuum line in the cabin though. I guess it is higher up than I can see.
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
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I'm pretty sure the fox cars have a vacuum canister, this will hold a vacuum for a short period that will allow a change in function maybe even a few times before losing it.
I have a 95 and the dash is pretty much destroyed so it may be a matter of just looking between the gaping cracks.
It's at the shop so it will be tomorrow.
 

revhead347

Just rub Vaseline all over
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It's a common problem. The vacuum line from the vacuum tree to the HVAC box is leaking. When the system has no vacuum, it defaults to defrost. The good thing is that the line almost always brakes under the hood, not under the dash, because that is where the most heat is.

Kurt
 

Nocturne13

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It's a common problem. The vacuum line from the vacuum tree to the HVAC box is leaking. When the system has no vacuum, it defaults to defrost. The good thing is that the line almost always brakes under the hood, not under the dash, because that is where the most heat is.

Kurt

Do you know where it ends up in the dash and what has to be removed to do the job on the 1994GT? My line runs from the vacuum tree and goes straight through the firewall on the passenger side - I can't replace it wo going into the dash area somehow. I can't find it by looking up from the passenger floorboard and I can't find anything online or in my manual that shows where the vacuum line ends up. Does the entire dash have to come out? I am ill so some jobs are a little out of reach for me physically but I desperately need AC for the same reason. Thank you!
 

revhead347

Just rub Vaseline all over
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If the line under the hood isn't broken or leaking, the lines under the dash are in a multicolor bundle. You can follow them back from behind the HVAC mode selection switch.

Kurt
 

Nocturne13

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Wanted to thank everyone who replied to help. I think it was actually where the vacuum lines connected. The lines had just opened up a tiny fraction at the ends over the years and the connections were just loose enough to allow a vacuum leak after several miles of driving. Put a spring clamp at the vacuum tee and have new silicone hose coming. I am way too dumb to have figured this out without help and am very grateful.
 
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General karthief

wonder how much it would cost to ship you a pair
Mod Dude
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Most of us started out a little dumb, it's not brain surgery but it can make your brain hurt.
Glad you got it figured out and we (not necessarily me) could help.
 

Chythar

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Lack of knowledge or experience is not dumb. We're all hear to learn, and those of us that know things are happy to pass the knowledge on.

Be careful of the silicone hoses. If the walls of the hose are too thin, they may collapse under vacuum and will cause issues.