A/C Help

[ResurrectionProject]

94 5.0 5spd.
Working on getting the A/C blowing cold per the wife’s request.
I have so far confirmed low pressure switch working, CCRM working and found a leak.
Right now the clutch will engage for 1 second and then disengage for 10 seconds and repeats that.
Suggestions on what may be the cause?

 

[lwarrior1016]

94 5.0 5spd.
Working on getting the A/C blowing cold per the wife’s request.
I have so far confirmed low pressure switch working, CCRM working and found a leak.
Right now the clutch will engage for 1 second and then disengage for 10 seconds and repeats that.
Suggestions on what may be the cause?

Have you put a set of gauges on it to see what the pressures are? High and low side.

 

[ResurrectionProject]

Have you put a set of gauges on it to see what the pressures are? High and low side.

First photo (low side showing vacuum) is with comp. clutch engaged.
Second photo is at idle without comp. clutch engaged

 

[lwarrior1016]

Looks to me like you need more refrigerant. The low side should be somewhere around 30-40 psi with the compressor running

 

[cobrajeff96]

If there is a leak, you must fix it. A leak will cause a drop in pressure and the A/C pressure switches will always command the compressor to disengage unless the system is literally air tight. The system's high and low sides must live within a controlled pressure range at all times when the compressor is active. More than likely every component is pretty old, so your best bet is to pony up and replace every line. If that's not in the budget, at least replace every green o-ring at each connection point. And once you get it right, turn on the A/C once every quarter, even in the winter. This circulates the PAG oil throughout the system and prevents these o-rings from rotting out and causing leaks all over again.

 

[MyLittlePony]

I would add more refrigerant. It’s not great for the environment, but 94 5.0 mustangs are great for it either. Basically, treat it like a slow leak. Every spring/summer, when finally needed, I would add it, and it would be enough to last till the cooler months. A few years ago, I started hearing a hissing noise from the AC drier. Upon inspection, I could see that some kind of liquid was seeping out. Replaced it, and the AC blew cold again.

Continued adding a can every year until it just wouldn’t blow cold anymore. Took it to a professional who determined that the evaporator core needed to be replaced. This is a procedure that will “total out” the car as pretty much the dash, seats, center console, everything, has to be removed to get to it. I was thankful enough to get my husband to do the work for me, but that meant that I was without the car for several months, so keep this in mind. That’s why I said just throw refrigerant at it until the bandaid no longer works.

Also want to mention some other AC related issues I experienced with my 94. The AC compressor went out twice. First time it seized up on me (convertible, so I didn’t use it often). The remanufactured one that replaced it also failed on me. Another thing is those high and low side valve caps. They get brittle after a while. Replacing those helped stop the refrigerant from leaking.

 

[cobrajeff96]

Keep in mind those caps are merely dust covers. The valves beneath them were leaking and needing replacement if the caps were the only things stopping those lines from leaking at those points. Unfortunately, most aftermarket crap is just that.

FWIW, there are vids on youtube for taking out an SN95 dash, and you'd be surprised how easy it is. If you're committed and serious about it, one hour max job (if in fact the evap core is leaking). Helps to have a helping hand for when it comes time for plucking it out and setting aside. But it's one of those jobs where you'd want to also replace a heater core while you're at it.

 

[Slice]

Personally I find trying to fix air conditioning on old cars you'll end up with more Hassle and dollars than the entire car is worth.

 

[MyLittlePony]

Personally I find trying to fix air conditioning on old cars you'll end up with more Hassle and dollars than the entire car is worth.

Where I live, functioning AC is more important as a safety feature than air bags. Lowering windows, (and putting the top down when applicable) doesn’t help if it feels like a hair dryer.

While yes, hiring out parts and labor will essentially total out the car, in environments like this, you either have a functional car with working AC, or part it out, and buy something from this decade which will just end up disappointing you in a year or so. I can’t imagine getting rid of my Mustang when I was informed that it was the evaporator core. But what good is a car you don’t drive? I already have a car like that. I rarely drive it because it gets so hot inside. AC was never an option from the factory or dealer. Don’t need two vehicles like that.

 

[MyLittlePony]

Keep in mind those caps are merely dust covers. The valves beneath them were leaking and needing replacement if the caps were the only things stopping those lines from leaking at those points. Unfortunately, most aftermarket crap is just that.

FWIW, there are vids on youtube for taking out an SN95 dash, and you'd be surprised how easy it is. If you're committed and serious about it, one hour max job (if in fact the evap core is leaking). Helps to have a helping hand for when it comes time for plucking it out and setting aside. But it's one of those jobs where you'd want to also replace a heater core while you're at it.

I think maybe the caps came with the valves. It was about 15 or so years ago. I just remember having to go to the dealer to actually pick up the part.

My husband took my dash out, and yes, I had to help him. It was heavy AF, and going back in caused it to crack. Thankfully, it was a small crack, near where it meets the windshield, and I was able to push it back down with super glue.

It was a huge ordeal because we ended up having to remove both seats and the very there console, and removal of the dash STILL caused damage to my shifter handle. It’s an automatic, so you really can’t find anything like it that’s new, and used, my damaged one still looked better. Thankfully, for Christmas, he had the leather tetrapod (that’s what was damaged. It had a giant gouge out of it)

But basically, I was without my car for months because he could only work on it during the weekends, but also, he was trying to get the aftermarket security system to work again. Anyway, I ended up missing the 2022 LMR Cruise In because of it. Thankfully I got to go in 2023 and 2024, but they’re not even having it this year.