How to Recharge Air Conditioning

[MRP78]

I want to recharge the A/C in a 1987 Turbo Buick. The compressor doesn't engage so I think there may be a leak but I'm not sure. I don't know if It has ever been recharged or when it may have been. If the compressor won't engage how can I pull in refrigerant, oil and leak detector to help see what might be wrong with the system?

 

[SS502]

On the a/c accumulator is the low pressure switch,unplug it and with a test light to ground check both terminals. one should have 12v. using a small jumper wire jump the 2 terminals and the compressor should engage. Don't know what the new switches go for, were about $12 last time I bought one, but a common part to go bad.

 

[charlief1]

This may help you with the wiring so you can figure out what's not working.

 

[scot w.]

I want to recharge the A/C in a 1987 Turbo Buick. The compressor doesn't engage so I think there may be a leak but I'm not sure. I don't know if It has ever been recharged or when it may have been. If the compressor won't engage how can I pull in refrigerant, oil and leak detector to help see what might be wrong with the system?

You compressor will not turn on because your charge is low and the "Low pressure switch" is now is doing it's job by locking it out. On the a/c accumulator (close to the heater box) is the low pressure switch with a round looking plug, unplug that plug and put a jumper wire in there with two male ends. This will bypass the low pressure switch to allow you to see if your compressor still works & engages. It will also allow the compressor to run so you to put a charge in the system.

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[MRP78]

Thanks for the tips. I'm hopeful and pretty sure it's just very low on freon. Is there a way I could use a vacuum pump to vacuum out the system 1st and if so how is te best way to do it?

 

[MRP78]

Is there anything special involved in replacing the low pressure switch? Does it automatically need to be replaced if the system gets too low?

 

[scot w.]

Is there anything special involved in replacing the low pressure switch? Does it automatically need to be replaced if the system gets too low?

No it usually does not need replacing as it's just that, A switch! If you do the test I mentioned above that will confirm that your system was out on "Low pressure" and the system is low on freon. It will also let you know if your compressor still works. Once yo determined those things I would just take it to a place that charges car A/C systems and let them do everything for you but tell them it was out on Low pressure and the leak will have to be found first before charging the system back up.

.

 

[standupjskiguy]

Oil is circulated with the freon. The low pressure switch keeps the compressor from running without freon and hence oil to protect it. If you confirm with a gauge that the car is low on freon, you don't need to change the low pressure switch.So no, it doesn't need to be changed because the system got low.

 

[MRP78]

It was very low on freon. Everything works fine for now. I had some R12 so I charged it up and it's very cold. I think it may have a leak at the base of the lower smaller metal A/C hose at the evaporator core. I'm not sure what this hose is called and am wondering what it may take to repair a leak on this line.

No it usually does not need replacing as it's just that, A switch! If you do the test I mentioned above that will confirm that your system was out on "Low pressure" and the system is low on freon. It will also let you know if your compressor still works. Once yo determined those things I would just take it to a place that charges car A/C systems and let them do everything for you but tell them it was out on Low pressure and the leak will have to be found first before charging the system back up..

 

[scot w.]

It was very low on freon. Everything works fine for now. I had some R12 so I charged it up and it's very cold. I think it may have a leak at the base of the lower smaller metal A/C hose at the evaporator core. I'm not sure what this hose is called and am wondering what it may take to repair a leak on this line.

Glad it's working again...

 

[SS502]

Glad it's working again...

X2, wasn't saying switch was bad, just giving options & info.

 

[MRP78]

Thanks for all the help and tips.

Anyone know what the lower metal line that goes into the evaporator core is called and what may be required to repair it if it has a leak?

Here's a picture it's the lower smaller hose that bends down. I heard some hissing at its base where you see a split in the insulation around It at one point yesterday during recharge. Saw some moisture in the same spot but that was probably condensation.

 

[standupjskiguy]

Hissing may be normal as the high pressure gas expands thru the expansion orifice into the evaporator.
Give the system time and if it gets low again in a short time, then you've got a leak.
BTW all systems loose charge over time and even faster if they are not run regularly.
You would be wise to get a set of gauges.
But at least get a thermometer to check the vent temperature.
If you have a 20 degree drop from ambient temperature, the system is working OK.

 

[MRP78]

What are the most common places these systems leak from? What's the best way to find where it's coming from? The last charge I put in lasted a little under a year so there must be a leak somewhere.