Wife furious with me... HVAC question!

[Todd82TA]

Hey guys... I hope you can help me... 2009 Ford Explorer XLT Sport 4.0L / 2WD

4 months ago, my Air Conditioning "stopped working."

Here's some background... it's totally original, everything was working fine, but I started hearing a "hissing" sound under the dash as I would accelerate. In all my years of working on cars, I immediately recognized this as a slight vacuum leak related to the HVAC control system (I'm guessing it uses engine vacuum to control the various flaps and such).

Ok, so I kind of thought it was cool, and ignored it. Then one day, the Air basically stopped working. I topped it off with some "quick fix" R134A. I think one of the problems is that it has "stop leak" in it (which I shouldn't have gotten)... and now the A/C compressor cycles A LOT... I mean, a lot, and quickly... like... on for 2 seconds, off for 2 seconds, on for 2 seconds, off for 2 seconds.

I basically don't get any air in the car... to the point that I actually get hot air. It occurred to my daughter one morning when I was driving her to school that the passenger side gets COOL air (not freezing, just cooler than ambient outside), and the driver's side gets hot air. I got to thinking and now realize that the problem is likely the vacuum leak in the HVAC controls... more than likely, the blend door or whatever door it is that closes off the flap that goes to the outside or the heater core has likely gotten stuck (or no longer working because of the vacuum leak). Now... this wouldn't cause the compressor cycling. This may seem funny, but I actually have an MVAC license (grandfathered in) because back in the early 2000s I got a license and took the test so I could buy R12 for my Fiero... but clearly, I have no idea what I'm doing:


So my questions are:

- Am I likely correct in my assessment that the vacuum controls are busted and I'm getting hot air from the heater core and not actually getting any cool air from the A/C system? If yes... where exactly do I go to address this? Do I need to remove the entire dash, can I get to it from the engine bay? Or is this one of those sit upside down and backwards in the passenger seat and remove the heater core box kind of thing?

- With the compressor constantly cycling, have I basically clogged up the lines? Is it the expansion tube (filter) that I need to replace? And then... can I merely clear the lines (and how do I do this) and then vacuum out by -5 mercury and then have some A/C shop recharge the system?



Looking for advice... I really, really appreciate any help. Thank you!

Also, damn... what happened to all the ads? This is a great website, but it's almost unusable with all those ads. I'll go sign up for the Elite Explorer thingy cause damn... there's waaay too many ads.

 

[94Eddie]

There is a vacuum reservoir under the dash on the passenger side. It is meant to maintain vacuum in the system when the engine is under load (i.e. the engine no longer makes a vacuum). It might be cracked and leaking. Also, doing a smoke test should pinpoint where vacuum leaks are occurring.

 

[GB1977]

We had something similar when we first bought ours....Hissing was the HVAC system defaulting to the defrost position and we could get nothing out of the vents. Apparently this is a fail safe position so that the car is at least safe to drive by clearing the windshield. My mechanic at the time spotted it quickly and it was a cheap fix. check valve or something if I recall correctly.

 

[94Eddie]

We had something similar when we first bought ours....Hissing was the HVAC system defaulting to the defrost position and we could get nothing out of the vents. Apparently this is a fail safe position so that the car is at least safe to drive by clearing the windshield. My mechanic at the time spotted it quickly and it was a cheap fix. check valve or something if I recall correctly.

This happened to me also. A $10 check valve fixed the problem. I don't think the OP has this issue since the air is not bouncing back and forth from the defrost to the dash vents. Although the hissing while accelerating is a symptom of a bad check valve and would be worth investigating.

2009 Ford Explorer

2009 Ford Explorer Owner having issues with air not coming out the vents when motor is under pressure.

www.explorerforum.com

 

[FordFlintrock]

Your compressor is short cycling which usually but not always signals a low charge of refrigerant. A gauge set with low and high side pressures will tell the tech if it is low or high side pressure which is causing the cut-out. Is your radiator fan turning ON? There are 2 ways to know how much refrigerant is in a system. 1st is if the system operates as designed with good pressure readings it can be assumed everything is up to snuff with full charge. 2nd is to weigh it on a scale during recovery and to weigh it when charging with leak testing done prior to fill. Topping off is what we did with R12 back in the day with a few ounces over or under could always get it down to 35° vent discharge give or take. Modern systems are more sensitive to charge weights. Now that R1234y is here at $50/lb. wholesale, leaks will get very costly.
The stop leak prolly not causing any problems but charge weight must be correct. A quick test to see if heater core is an issue is to use a pair of long nose vise grips and clamp down one or both of the heater core hoses, no flow no heat. As mentioned earlier the vacuum check valve needs to be looked at.

 

[94Eddie]

To build on what FordFlintrock said, I had a similar issue as the OP in that the passenger side was cooler than the driver side when the AC was running. Neither side was as cool as it should have been. There refrigerant pressures were fine, no leaks etc. The problem turned out to be a weak compressor that was well on its way to taking a dirt nap. Installing a new compressor solved the problem and things have been ice cold ever since.

 

[FordFlintrock]

To build on what FordFlintrock said, I had a similar issue as the OP in that the passenger side was cooler than the driver side when the AC was running. Neither side was as cool as it should have been. There refrigerant pressures were fine, no leaks etc. The problem turned out to be a weak compressor that was well on its way to taking a dirt nap. Installing a new compressor solved the problem and things have been ice cold ever since.

Not long ago I was asked to diagnose an A/C problem on a 85k 2015 F150 8cyl Florida truck. I was assured nobody had messed with it and it was working properly for the previous 2 years when they bought it. Complaint was low cooling, high speed fan roaring when A/C on and fast clutch cycling. Truck was sitting outside for at least 30 minutes when I hooked my gauges up, lo and behold the high side was at 375psi. That told me there was an obstruction in the system with no equalization through the compressor or expansion block. I started it up pressure went to 425 before high pressure shut it off again.

I have literature from compressor manufacturers that if a compressor can build 400-425psi there is nothing wrong with it, claim denied. Well obviously there was a reed valve problem in this one. I was originally thinking the desiccant bag blew apart causing a blockage and told them to order a compressor, condenser and expansion block kit, I was only going to do this once. After parts replaced and no finding of obstruction cold as ice. Testing compressor high pressure is accomplished by blocking airflow or disabling electric fan.

 

[94Eddie]

Not long ago I was asked to diagnose an A/C problem on a 85k 2015 F150 8cyl Florida truck. I was assured nobody had messed with it and it was working properly for the previous 2 years when they bought it. Complaint was low cooling, high speed fan roaring when A/C on and fast clutch cycling. Truck was sitting outside for at least 30 minutes when I hooked my gauges up, lo and behold the high side was at 375psi. That told me there was an obstruction in the system with no equalization through the compressor or expansion block. I started it up pressure went to 425 before high pressure shut it off again.

I have literature from compressor manufacturers that if a compressor can build 400-425psi there is nothing wrong with it, claim denied. Well obviously there was a reed valve problem in this one. I was originally thinking the desiccant bag blew apart causing a blockage and told them to order a compressor, condenser and expansion block kit, I was only going to do this once. After parts replaced and no finding of obstruction cold as ice. Testing compressor high pressure is accomplished by blocking airflow or disabling electric fan.

I had a local repair shop that I trust do the repair because I have no business diagnosing and repairing an AC system. I had not heard of a weak compressor before but with a little snooping around on the FordTechMakuloco YouTube channel I confirmed it is possible. A new compressor definitely solved the problem.

The repair shop I use is owned by a Korean guy and the people that work there are all Koreans. They are constantly loaded up with work. I am amazed at how fast they get repairs done. I had them replace all the struts on my Mountaineer. I dropped it off at 8:00 am and they called to tell me it was done before noon. Plus, they only have three bays in their shop and one of them is dedicated to state inspections.

 

[Josh P]

Could you jumper the low pressure switch to see if the compressor stays on for more than 2 seconds?