OT - Vehicle AC System - Help a buddy out?

[HoosierBuddy]

Hey guys...this is sort of on topic in a very roundabout way. I have an ac system in my garage right now that isn't working.

It's in my kid's Fox mustang though.

This is an R134A kit that was installed in the car about 12 years ago. I put it in the car at the time, and still have the original instructions, but they are terrible. To add issues, when the unit crapped out a few years later I took it to a garage and that guy made some changes (after consulting "Hose Wizards" who built the system but is no longer in business.

Questions:

1. As installed (with a Sanden compressor) the unit initially included a binary switch on the high pressure hose that served as both a low pressure and high pressure cut off to the compressor clutch. This was in place of the factory low pressure switch on the drier, which was bypassed by the new system. HOWEVER, when the system was updated, the garage guy installed a low pressure switch rated for the higher R134A pressures in the drier and (I THINK) left the binary switch disconnected completely.

Does that make sense? Can an R134A system operate safely with only a low pressure cutoff and without a High Pressure cutoff?

If I have to, I can use both. The binary switch is still there. I just don't think it was wired up....but I'm not 100%.

2. I had to pull the engine when it ate a lifter and wiped a lobe on the camshaft. I unbolted the compressor and left it in the engine bay during the R&R to preserve the freon charge, but at some point the freon bled off....like completely. I checked last night and my gauge shows zero point zero.

Can I buy a vacuum pump, pull this thing down, check for leaks, get a set of gauges/hoses and recharge this thing myself with R134A? I know they say you have to have someone evacuate the system so the R134A doesn't leak to atmosphere, but that ship has sailed. Any remaining roadblocks to DIYing this sucker? I wouldn't mind buying the tools including a vacuum pump. Technically my kid is paying for this, since it's his car. But if I DIY it....he'll only end up paying for the freon and I'll pay for (and get to keep) the tools for future projects.

If I go that route, can I "assume" that all or most of the compressor oil is still in the system. The freon apparently either leaked off over time before the engine issue OR possibly leaked out due to the low pressure fitting at the compressor getting loose as I maneuvered that unhooked compressor around as the engine came out. I noticed that fitting was loose when I reinstalled the compressor on the engine after i repaired it. It's possible that since it was loose, freon was able to sneak past the o-ring.

Thanks in advance for any help!

 

[428PI]

There's no way a "binary" switch can be both a high pressure and low pressure switch in the same hose unless it's designed to kick the compressor off if it got real low on freon (not to regulate it though). I would use it if you have it. What kind of fan are you using to cool the engine and ac condensor? That would be my question. You want a fan that will pull good air all the time and not just some of the time. You may run into problems if you rely on a mechanical fan that doesn't pull enough air. The low pressure switch is used to regulate the on time of compressor. Once ambient air temp is above 85 to 90 degrees the compressor should stay on all the time. Below that it should start cycling. If it doesn't the evaporator could freeze up and you lose air flow. Yes, pull a vacuum, recharge and see what happens. If you didn't see any oil come out anywhere you're probably ok OR they didn't put any oil in system. It's a guess. You can buy a vacuum pump that runs on shop air (if you have at least a 6 cfm compressor or so) to pull a vacuum. I purchased mine at HF. Did they have a sticker somewhere showing the proper fill?

 

[dogdog]

I would first know your compressor first. Sanden have great information and service manual for some of their compressors. Dependents on your model of cause. Like for my be they used SD7v16 and I just googled “sanden SD7v16 service manual”. Maybe you can find something there. If it is something factory, they should have a description and function of that component.


The basics of automotive ac, it’s pretty comprehensive.

Ariazone International Pty Ltd

Our innovative range of refrigerant processors ensures you are offering your clients the best service possible.

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[HoosierBuddy]

There's no way a "binary" switch can be both a high pressure and low pressure switch in the same hose unless it's designed to kick the compressor off if it got real low on freon (not to regulate it though). I would use it if you have it. What kind of fan are you using to cool the engine and ac condensor? That would be my question. You want a fan that will pull good air all the time and not just some of the time. You may run into problems if you rely on a mechanical fan that doesn't pull enough air. The low pressure switch is used to regulate the on time of compressor. Once ambient air temp is above 85 to 90 degrees the compressor should stay on all the time. Below that it should start cycling. If it doesn't the evaporator could freeze up and you lose air flow. Yes, pull a vacuum, recharge and see what happens. If you didn't see any oil come out anywhere you're probably ok OR they didn't put any oil in system. It's a guess. You can buy a vacuum pump that runs on shop air (if you have at least a 6 cfm compressor or so) to pull a vacuum. I purchased mine at HF. Did they have a sticker somewhere showing the proper fill?

My understanding is the binary switch was designed to cut power to the compressor clutch if the freon got low (Low pressure cut off) AND cut off power to the clutch if the pressure gets too high. Based on the wiring diagram, the high pressure cut off was not included by the OEM R12 system. Somewhere in my reading I think I came to understand that the R134A systems run at a higher pressure, so perhaps that's why it became a concern?

The system was designed for and sold to Fox Mustang owners by one of the more reputable Mustang specific supply catalogs. Fox mustangs came equipped with mechanical fans with the old-style thermostatic clutch to allow the fans to free-wheel until the engine bay heats up. This particular system worked pretty well when new and again pretty well after the mechanic got done with it.

Typically this car stays at my son's house 2 hours away from me. The first time I'd driven it in years was after I got the engine reinstalled, so I don't know if the system was working at the time the engine failed or not. I do know that after I got the engine back in the wiring to the compressor clutch seemed to be missing part of the harness. So, I've ordered the factory connector (should be here Tuesday) to mate up with the OEM wire that is hot (12 V) if ALL the following conditions are met:

1. Engine is running.
2. ECU says engine is not at WOT.
3. AC Control is switched to AC, MAX AC, or defrost.
4. Low Pressure switch at AC drier is closed.

So as I have to recreate the wiring from that point, my question really boils down to should I hook that output directly to the green wire (Clutch Power) on the Sanden OR should I run it to the input of the binary switch and then onto the Clutch. That would mean the following two conditions would also have to be met for the compressor to run.

5. Binary switch says R134A pressure is Above 30 PSI
6. Binary switch says R134A pressure is Below 400 PSI

I'm leaning towards wiring it through the binary switch too. Even if it's not 100% necessary, seems like it wouldn't hurt anything...and maybe it is necessary???

 

[428PI]

If using mechanical fan I would hook up the binary switch for safety's sake. I do know that my early 94 Crown Vic's that had 134a didn't cool very good at idle speed in gear probably due to the fact that the clutch fan wasn't doing much and on occasion would kick out ac for awhile. I had the same problem on my 83 Ranger Diesel with R12. Later cars and pickups with electric cooling fans tend to do better.

 

[snyder]

Once you actually get freon going in you can jump out the pressure switches to keep the compressor going. After you get a full charge it will be easier to troubleshoot the electric side of operation.

 

[fitter30]

Since there wasn't any refrigerate in the system i would want to pressurised with nitrogen for leak checking. Be sure to pull a wire so the compressor won't run. Then evacuate and charge 80% of r12 for a start.

 

[Wrench97]

There's no way a "binary" switch can be both a high pressure and low pressure switch in the same hose unless it's designed to kick the compressor off if it got real low on freon (not to regulate it though). I would use it if you have it. What kind of fan are you using to cool the engine and ac condensor? That would be my question. You want a fan that will pull good air all the time and not just some of the time. You may run into problems if you rely on a mechanical fan that doesn't pull enough air. The low pressure switch is used to regulate the on time of compressor. Once ambient air temp is above 85 to 90 degrees the compressor should stay on all the time. Below that it should start cycling. If it doesn't the evaporator could freeze up and you lose air flow. Yes, pull a vacuum, recharge and see what happens. If you didn't see any oil come out anywhere you're probably ok OR they didn't put any oil in system. It's a guess. You can buy a vacuum pump that runs on shop air (if you have at least a 6 cfm compressor or so) to pull a vacuum. I purchased mine at HF. Did they have a sticker somewhere showing the proper fill?

They used them on older trucks, either a trinary or binary switch they can be used to as a low pressure switch as in if the pressure is below 40 psi it will not allow current to flow and engerize the clutch good for low temps(winter operations) and low refrigerant levels, the binary shuts the compressor off if the high side is too high.
The trinary can also be used to control the cooling fans if needed.

 

[Wrench97]

My understanding is the binary switch was designed to cut power to the compressor clutch if the freon got low (Low pressure cut off) AND cut off power to the clutch if the pressure gets too high. Based on the wiring diagram, the high pressure cut off was not included by the OEM R12 system. Somewhere in my reading I think I came to understand that the R134A systems run at a higher pressure, so perhaps that's why it became a concern?

The system was designed for and sold to Fox Mustang owners by one of the more reputable Mustang specific supply catalogs. Fox mustangs came equipped with mechanical fans with the old-style thermostatic clutch to allow the fans to free-wheel until the engine bay heats up. This particular system worked pretty well when new and again pretty well after the mechanic got done with it.

Typically this car stays at my son's house 2 hours away from me. The first time I'd driven it in years was after I got the engine reinstalled, so I don't know if the system was working at the time the engine failed or not. I do know that after I got the engine back in the wiring to the compressor clutch seemed to be missing part of the harness. So, I've ordered the factory connector (should be here Tuesday) to mate up with the OEM wire that is hot (12 V) if ALL the following conditions are met:

1. Engine is running.
2. ECU says engine is not at WOT.
3. AC Control is switched to AC, MAX AC, or defrost.
4. Low Pressure switch at AC drier is closed.

So as I have to recreate the wiring from that point, my question really boils down to should I hook that output directly to the green wire (Clutch Power) on the Sanden OR should I run it to the input of the binary switch and then onto the Clutch. That would mean the following two conditions would also have to be met for the compressor to run.

5. Binary switch says R134A pressure is Above 30 PSI
6. Binary switch says R134A pressure is Below 400 PSI

I'm leaning towards wiring it through the binary switch too. Even if it's not 100% necessary, seems like it wouldn't hurt anything...and maybe it is necessary???

Belt driven cooling fan or electric?

 

[HoosierBuddy]

On a fox mustang, the cooling fan is mounted to the water pump pulley and turned by the serpentine belt.

 

[Wrench97]

On a fox mustang, the cooling fan is mounted to the water pump pulley and turned by the serpentine belt.

So stock fan set up, the high side switch is there only to shut the compressor off if the temp/pressure gets too high.

Wire it through the binary to protect the system.

 

[HoosierBuddy]

So stock fan set up, the high side switch is there only to shut the compressor off if the temp/pressure gets too high.

Wire it through the binary to protect the system.

Will do.

I actually think I figured out how it was wired at the time the engine gave out. It looks like the mechanic installed the low pressure switch in the drier, and then hooked the factory harness "Hot" wire into the binary switch by jamming a stripped wire end from the switch pigtail right into the female slot in the factory harness.

I've got the actual factory connector pigtail on order that will allow me to clean that up and do it right. That will put the binary switch in the circuit as you suggest.

After that, I'll either take it somewhere for leak check/recharge or do it myself. Kind of leaning towards DIY.

 

[HoosierBuddy]

Got it wired up and purchased some R134A and the hose kit to check and recharge.

I checked with my kid and he reports the AC has not worked for some time...so decided to find the leak.

I pressure tested to 100 PSI using a bottle of CO2 I had here. I sprayed down everything and couldn't find any leaks. The next morning it only had 50 PSI in it.

I took the CO2 off....added a small about of R134A dye and repressurized, Then I started the engine, and kicked on the compressor to stir the dye into the system. After a minute I shut it down.

Dye was leaking out of the rubber cover on top of the binary switch. I had to disassemble the air intake on the car to get my hands on the switch, but once I pulled the cover off, I could see dye pushing out between the plastic switch body and one of the terminals. Must be cracked.

That switch mounts to what I believe is an R12 service port and seals to it with an o-ring. I unscrewed it, noted the pressure ranges it kicks off on low and high and found a replacement online at Summit and have it ordered.

I'm stuck now waiting on parts.

 

[Wrench97]

That is a common issue with those, I changed one and the connector on a 93 Town Car yesterday along with a bad radiator fan clutch.....................wanted to change the expansion valve also but the line is corroded too bad to get apart without destroying it, customer decided to live with 50 degree air

 

[doyle]

Harbor Freight has a good electric vacuum pump that's fairly inexpensive that would be worth buying, and get your a/c gauges at either ORILEY'S or NAPA, harbor freight's are junk. After you have finished your repairs I would install 2 cans of freon first then check pressures, the low side pressure you want it to read 34 to 36 psi and the high side pressure you want it to read 225 to 250 psi. You should have these readings when engine is at operating temp and windows rolled down on a hot day, with R134 you want to leave the charge a little low because it expands as it heats up and doesn't cool as good. your low side pressure switch needs to be adjusted so it cycles the compressor clutch if it gets down to 28 psi.

 

[HoosierBuddy]

Pardon Our Interruption

That was the best (closest) switch I could find as a replacement.

The a/c is up and running good now. I got my hose kit and vacuum pump off amazon. Not sure it was the best but it got good review and worked fine.

QUESTION: How are you supposed to attach the can tap to the top of the 12 ounce R134A can without super-cold freon shooting everywhere? I made quite a mess and likely lost 1/4 of my freon just getting the can tap screwed onto the can.

I must be doing something very wrong.

 

[Wrench97]

Did you unscrew the piercing pin valve before installing the top?

Is there a rubber gasket inside the tap where it seals the top of the can?

 

[HoosierBuddy]

Did you unscrew the piercing pin valve before installing the top?

Is there a rubber gasket inside the tap where it seals the top of the can?

I think you've hit on my problem. I was treating the valve as a "valve", screwing it completely closed before installing it. Now that I've looked at it closer I see that you are supposed to turn the valve to the normal "open" position, which retracts the pin before putting it on the can.

My only excuse is my setup included no instructions, and I didn't realize this is not really a "valve" in the normal sense and is operated ***-backwards from how you would intuitively think it would operate.

If I was the engineer that designed the tap, I would have reversed the thread....but in the meantime I guess we just need to get the word out that if you think of the tap as a "valve" you operate it exactly backwards of a normal valve.

This also explains why my fill was very slow, as I had the pin most of the way retracted while attempting to charge.

 

[Fasthotrod]

...I didn't realize this is not really a "valve" in the normal sense and is operated ***-backwards from how you would intuitively think it would operate.

....but in the meantime I guess we just need to get the word out that if you think of the tap as a "valve" you operate it exactly backwards of a normal valve.

This also explains why my fill was very slow, as I had the pin most of the way retracted while attempting to charge.

No sir... that is not correct.

A piercing valve does work like a regular valve, but the first step is to 'open' the valve so that it retracts the pin and does not pierce the can until the valve is completely seated into place on top of the can.

Once the can is in place, you 'close' the valve completely so that the pin pierces the can, and the actual internal part of the valve is closed. It now operates as a regular valve.

When you go to charge the system, you open the valve to start the filling process. (Assuming that you purged any air from the lines/gauge set.) When you have reached the proper amount of refrigerant, you close the valve and remove the gauges and line set.

If you used a newer can of R134a, it may be the new EPA required design that does NOT use a piercing valve, and has an internal Schrader valve. That will cause you some fits as well unless you have the correct style valve to open it.

This video does a good job explaining the differences, and how they work:

Hope this helps.

Mark

 

[75gmck25]

I've run into confusion with the old R134a cans that use a piercing adapter, vs. the newer cans that have an internal valve that is pushed down by the adapter as you screw the pin down.

-- Old cans and adapters - unscrew the piercing pin as far as possible, screw the adapter onto the can, screw the piercing pin down to puncture the top of the can and fill R134a. Once you mount the adapter you cannot take it off without releasing all the R134a from the can.

-- New cans and adapters - unscrew the pin valve as far as possible, screw the adapter onto the can, screw the pin valve down to push down the internal can valve and fill R134a. When you are done, unscrew the pin (internal can valve now closes) and remove the adapter.

All directions for R134a conversions will recommend adding a high pressure cutoff valve, but based on my limited experience it may not be that critical. Most of them are preset for 300 psi or higher, and I've never seen my high pressures hit that level.