Automotive Air Conditioning Information Forum

That’s a tough one… and honestly, you’ve already gone way deeper into it than most people would.
At this point, it really doesn’t feel like the HVAC module itself - 4 replacements all doing the same thing is a big clue. Feels more like something making the module lose its mind.
The way it switches ...

....have you checked the cabin air filter? A partially clogged or fully clogged filter sometimes can really throw-off an MVAC system. No, have not replaced (or even checked) the cabin filter in half a dozen years. Never considered that the filter could be a culprit. EDIT turns out the filter was ...

The part you describe is what I refer to as the blend door actuator, replaced twice, second time purchased a Motorcraft branded actuator (apparently the Murray branded part I first purchased was reported to be a bit flakey). When I replaced the HVAC control module, I followed the Ford calibration ...

2011 Fusion SE 4 cyl, base A/C (not dual zone, not auto temp control). 175K miles. A/C appears to work good, nice cool temps out of the vents. Suddenly the A/C quits cooling and maximum heat comes out of the vents. A/C controls have not been touched when this happens. On a restart A/C may work fine ...

Thank you all for responding. If/when I need to use a sniffer in the future, I'll probably buy the 43-MT1734.

I got lucky recently when I could not find the leak (nitrogen pressure drop, leak detector fluid not showing any bubbles, sniffer not producing results on a partial charge) - I added dye ...

I purchased a TIF5550 sniffer used at an auction when the Penske Auto Centers at Kmart closed - this was an impulse purchase, I was at the auction to buy a service lift. This was in 2002 so the sniffer is at least 21 yrs old now. The sniffer never produced repeatable results. This summer I really ...

My Robinaire 2.2 cu in vacuum pump has become erratic and no longer draws below 1200 micron, at best. I completed 4 successive oil changes with no improvement. Are these pumps rebuildable by an individual? I searched for a repair kit or instructions for my pump and found nothing. I did find that ...

That takes care of the low hanging fruit. Do you have or can you borrow a sniffer?

You can as has been suggested add a couple of ounces of R134 and pressurize the system with nitrogen to 150psi for the sniffer.


I have a leak detector (TIP 5550) but it appears that as a minimum it needs a new ...

Leaks at service valve connections, service hoses and the test manifold are not uncommon.

I usually screw the high and low side hoses to a tube union and pull a vacuum on a gauge set as a test.


I pressure tested my gauge set at 150 psi and the pressure held steady for 2 hrs and I deemed that ...

A system that holds vacuum is no guarantee that it will also hold pressure. Did you try leak-testing the system using an electronic detector ("sniffer"), generally more sensitive than other methods?

You pressurized the system to 150 PSI using nitrogen the first time (pressure held). Then you ...