A/C not working - where to begin

[Fairlaniac]

In December I bought my current beater truck. A '91 SuperCab 4x4 2.9/5 spd. Now it's time to tackle the non-working A/C. All I can say it when I turn on the A/C absolutely nothing happens. I do not hear any noise at the compressor. So where do I start?

Thanks,

 

[adsm08]

If I knew nothing about A/C and had no tools to work on A/C I would start at a repair shop that is equipped to handle A/C problems.

 

[Fairlaniac]

Too easy!

If I knew nothing about A/C and had no tools to work on A/C I would start at a repair shop that is equipped to handle A/C problems.

That's the easy way out!

I can do most anything on a car/truck. Never tackled non-working A/C.

 

[adsm08]

Well the absolute first thing to do when dealing with an inoperative A/C system is to make sure that the system is charged correctly. The only real way to do that is to evac, vacuum, and recharge it.

I'll bet that you don't have access to an A/C machine.

 

[Chris_North]

ACs have a pressure control switch. If there's no refrigerant, it won't kick on. It's difficult to know what's going on refrigerant wise without specific tools. Fast, dirty, cheap and illegal way to check would be to unscrew the plastic cover for the charging/testing port (it should be close to the accumulator, a large black canister with A/C lines coming out of it, probably close to the heater core), then wearing heavy gloves use a small screwdriver to press in the little pin under that cap. All that pin is is a schraeder valve (like to fill your tires) but if your system has any charge left by quickly depressing that pin it will shoot out some of the freon. If nothing comes out then you have no charge, and thus probably also have a leak someplace. If you do get gas you might be either really low or have an electrical/control problem. It's not a sure thing either way but it's somewhat of a start.

Don't forget the gloves. It's unlikely to occur with just a bit of it but direct exposure to refrigerant will cause frostbite.


Edit: I am a slow typist....

I would have to agree with adsm08 though. This is a special tools kind of job, and everything you'll need is not cheap or useful for anything else (unless you do HVAC for a living, but I suspect you don't). Technically IIRC you should have an EPA 609 certification to touch this kind of stuff legally anyhow.

 

[alwaysFlOoReD]

I don't know much about AC but couldn't he check to make sure the electrical portion of the system is working?

Richard

 

[adsm08]

I don't know much about AC but couldn't he check to make sure the electrical portion of the system is working?

Richard

It is hard to check the electrical portion without potentially doing damage to the system unless he knows for sure that it is charged. The low pressure switch shuts down the electrical system when the system charge gets low.

About all he can do without running the compressor dry (think about draining all the oil out of your engine and starting it) is to check the continuity of the switch on the dash and then with the engine off jump power and ground to the compressor and see if the clutch kicks on.

 

[Chris_North]

I suppose one could jump out the clutch to get the compressor to engage. I am not entirely familiar with how the clutch is controlled but it looks simple enough. I wouldn't run it for more than a few minutes though if it's not working.


Haha, once again, I typed too slow.

You'd definitely know more about Fords adsm so I'd definitely err to your knowledge on the subject. It's not the same animal, but hermetic and semi-hermetic compressors I have worked on have survived running with no charge for a long while. The only thing is, as you have said, there is no way to know that there is sufficient oil in the compressor. The oil is carried with the refrigerant and if a major leak were to have occurred it is likely that a majority of oil was lost with the refrigerant. However since the system is already non-functioning IMHO the risk of taking out the comp might be a non-issue anyhow.

 

[Fairlaniac]

A/C

Well the absolute first thing to do when dealing with an inoperative A/C system is to make sure that the system is charged correctly. The only real way to do that is to evac, vacuum, and recharge it.

I'll bet that you don't have access to an A/C machine.

I bought a Robinair machine a few years ago at a garage going out of business auction. I'll have to did it out of the space above the garage and figure out how it works.

Thanks,

 

[adsm08]

I bought a Robinair machine a few years ago at a garage going out of business auction. I'll have to did it out of the space above the garage and figure out how it works.

Thanks,

I am both surprised and amazed.

The robinair machines are fairly straight forward, those are what we have a work.

You might also need to get some adapters if your machine is for 134 and not R-12 and your truck hasn't been converted.

Basically you hook up the lines to the truck, they only fit one way so you really can't screw that up, check gauges, hit recover, hit vacuum, let it suck, and then charge it up. R-12 to R-134 conversion is .9x. So you multiply the R-12 charge amount on the sticker by .9 to get the correct charge amount for 134.

 

[alwaysFlOoReD]

I bought a Robinair machine a few years ago at a garage going out of business auction. I'll have to did it out of the space above the garage and figure out how it works.

Thanks,

I relate to the way you think. I buy tools before I know what I'm going to use them for too.

Richard

 

[adsm08]

I would love to have my own A/C machine.

 

[Fairlaniac]

Fast, dirty, cheap and illegal way to check would be to ........................

I work like the government. If a company does the "right" thing you get polltion credits. I've been doing my part for the environment over the years I think I have a credit or two to spare by giving the schraeder valve a push or two ;-)

Thanks,