Engine A/C QUESTION

Mindseye007 · Jun 5, 2025

About 5 years ago I had purchased everything brand new for my 1991 5.0 coupe from summit to convert to R134, new compressor , lines , dryer. Condenser and had it installed and the A/C worked amazing for 6 months then one day I pulled out of my drive way and a weird sound came from the compressor and it sprayed up and Out of the hood on the drivers side area right where the compressor sits .....looked like I sprayed NOS so I took it back because it started blowing warm air with the A/C on and they could not find a leak so they recharged it. This happed a few times ..could it be a faulty compressor? Never heard that kind of sound before ....or should I just buy this kit from LMR. https://lmr.com/item/LRS-19703D-K/mustang-a-c-compressor-line-kit-87-93-5-0

RaggedGT · Jun 5, 2025

Sounds like it purged the refrigerant- likely pressures in the system getting to high

Mcmahst · Jun 5, 2025

Ok, wait, what? Never heard of that. It’s difficult to decipher your description of the problem and solution. Are you saying that after that happened your air conditioning didn’t work so you took it someplace and they added Freon into the system because it was low?

Mustang5L5 · Jun 5, 2025

Pressure relief valve on top of the compressor likely let go.

https://lmr.com/item/LRS-6888748/Mustang-A-C-Manifold-Service-Pressure-Release-Valve

The little cylinder with the white cap on the manfold above. Service pressure is 450psi before that lets go. Im pretty sure it's one time use, so you'll need to replace it.

Likely popped due to overcharging. Either too much refrigerant, or too much oil. Really need a set of manifold guages to se the high and low side pressure on a HOT day to see where you are at.

Mindseye007 · Jun 5, 2025

Mcmahst said:
Ok, wait, what? I've never heard of that. It’s difficult to decipher your description of the problem and solution. Are you saying that after that happened your air conditioning didn’t work so you took it someplace and they added Freon into the system because it was low?

No I took it back after it leaked the first time and they said they could not find any leaks so they refilled it up, and it worked again for a month, then it did the same thing .....made a weird noise and leaked...out

Noobz347 · Jun 5, 2025

Common issues with vehicle refrigerant/conversions:

If it charged multiple times by turning a can of refrigerant over to top it off and that can also contains [oil] then you end up in a situation where there's too much oil and not enough refrigerant. If using oil-free cans, this would not apply but the oil level should be checked.

R134 conversions from R12 should be service to 80% of specified value.

Mindseye007 · Jun 5, 2025

Mustang5L5 said:
Pressure relief valve on top of the compressor likely let go.

https://lmr.com/item/LRS-6888748/Mustang-A-C-Manifold-Service-Pressure-Release-Valve

The little cylinder with the white cap on the manfold above. Service pressure is 450psi before that lets go. Im pretty sure it's one time use, so you'll need to replace it.

Likely popped due to overcharging. Either too much refrigerant, or too much oil. Really need a set of manifold guages to se the high and low side pressure on a HOT day to see where you are at.

So you think the compressor is OK?

Mindseye007 · Jun 5, 2025

Noobz347 said:
Common issues with vehicle refrigerant/conversions:

If it charged multiple times by turning a can of refrigerant over to top it off and that can also contains [oil] then you end up in a situation where there's too much oil and not enough refrigerant. If using oil-free cans, this would not apply but the oil level should be checked.

R134 conversions from R12 should be service to 80% of specified value.

No they have an A/C machine they use at the place I took it to.

Noobz347 · Jun 5, 2025

Your [clutch cycling pressure switch] may be bad or intermittent (if it's shooting out of the relief valve):

Closes at 45 psi and reopens at 24.5 +/- 1.5 psi

Noobz347 · Jun 5, 2025

Also... Do you have electric fans? Do they kick on with your A/C?

2000xp8 · Jun 6, 2025

I've had this happen, it did most likely come out the pressure relief valve. That's why it lets you recharge it again.
Getting the refrigerant/oil and pressure right can be a little tricky.

Mustang5L5 · Jun 6, 2025

Mindseye007 said:
So you think the compressor is OK?

If it did shoot out of the relief, it's likely fine. Do you see any signs that it did? Does the spray patern match up?>

sparkylawdog · Jun 19, 2025

I Just had this same thing happen to my 85 GT. The system is still R-12. I've had the car since 2007 and the a/c has never worked. Had a bunch of a/c hoses, the evaporator (yes, that evaporator) and the condenser replaced late last year. Today it was hot enough to turn the a/c on, which was the first time since the work last year, Ran fine for about a mile, then poof, saw and heard the refrigerant come out from underneath the hood. I just can't catch a break.

nickyb · Jun 19, 2025

A little dye can go a long way to find the leak.

Mustang5L5 · Jun 19, 2025

The sniffer also works well. I bought a used commercial one on eBay and it’s saved me so much time.

Willybill32 · Jun 30, 2025

Sorry to take advantage of this thread, but I, too, have A/C questions.

My ‘86 5.0 has been getting some restoration work done, and I’m thinking about the A/C system. The evaporator coil was replaced when the heater core was replaced. More recently, while the radiator was out a new condenser was added. Last time it was all together, it was still R12, and it was recharged with R12, but apparently there was a leak. Now I want to go to R134A. The compressor, accumulator and pressure switch are the remaining R12 pieces. LMR.com sells a kit with the compressor, accumulator, lines and switch, but says it only fits ‘87-‘93, not ‘86. They sell the accumulator separately, but not the compressor. Would a new compressor from someone like Rock Auto work with R134A?

from6to8 · Jun 30, 2025

Just an FYI, when I did my 94 back in around 2021 I bought a kit that included the compressor and some other things and had a guy vacuum the system down, clean everything up real good and then recharge. Also bought an o ring kit, ect and everythign was pretty much new. Charged up and blew cold for some days and then warm again. Took it to a shop and they put in die. Blew cold for few days then warm again. They said it had to be the, whatever the part is in the dash and it would be $850 labor. I was like heck no and researched doing it myself. It's crazy how the heater core you can get to via a door but the other thing needed to be cut out and re sealed and sealed really really good. I didn't find where that was done too often and I had reservations about even doing it or that being it. Did som more research and came across something where someone changed the low and high pressure ports themselves and that's what I did. Through all of that I learned how to charge my own system and still blowing cold right now.

Fast forward 2-4 yrs later when time to build the 95 and the first thing I did was change those ports and it is still blowing cold 5 months later

Noobz347 · Jun 30, 2025

My 86 has all OEM parts plus an R134a conversion.

The conversion included:

2x new [screw on] adaptors for the charge ports
A conversion oil that is compatible with both, R12 and R134a
Getting the systems sucked down, new oil added, and service to 80% with R134a.

Still blowing cold some 15/20 years later.

At some point, I recall swapping the orifice tube but I [think] that was part of a repair that I did prior to converting to R134.

RaggedGT · Jun 30, 2025

Agreed with above- When I was converting them I was using a hybrid pag/esther oil -the fittings and clocking or changing the low pressure switch

Willybill32 · Jun 30, 2025

Noobz347 said:
My 86 has all OEM parts plus an R134a conversion.

The conversion included:

2x new [screw on] adaptors for the charge ports
A conversion oil that is compatible with both, R12 and R134a
Getting the systems sucked down, new oil added, and service to 80% with R134a.

Still blowing cold some 15/20 years later.

At some point, I recall swapping the orifice tube but I [think] that was part of a repair that I did prior to converting to R134.

I suspect my compressor needs rebuilding or replacing, hence the question about the compressor. Sounds like if the old compressor can work with R134A, then I could buy a new one and it should work with R134A as well?

Engine A/C QUESTION

Mindseye007

RaggedGT

Been here over a DECADE and still no CT

Mcmahst

Mustang5L5

That is…until I whipped out my Bissell

Mindseye007

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

Mindseye007

Mindseye007

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

2000xp8

Mustang5L5

That is…until I whipped out my Bissell

sparkylawdog

Active Member

nickyb

I gotta say i never painted my nuts, Never Ever

Mustang5L5

That is…until I whipped out my Bissell

Willybill32

But at least it's tight!

from6to8

There's suction so I used that end O_O

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

RaggedGT

Been here over a DECADE and still no CT

Willybill32

But at least it's tight!

Similar threads

Engine A/C QUESTION

Been here over a DECADE and still no CT

That is…until I whipped out my Bissell

Stangnet Facilities Maint Tech... Er... Janitor

Stangnet Facilities Maint Tech... Er... Janitor

Stangnet Facilities Maint Tech... Er... Janitor

That is…until I whipped out my Bissell

Active Member

I gotta say i never painted my nuts, Never Ever

That is…until I whipped out my Bissell

But at least it's tight!

There's suction so I used that end O_O

Stangnet Facilities Maint Tech... Er... Janitor

Been here over a DECADE and still no CT

But at least it's tight!

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