Car AC service, is the shop doing unnecessary work?

First of all would take it to another repairer as this one has not achieved anything except get lots of money off you. I would not short out the low pressure switch myself as I think they are there to stop the system from working should it be low on refrigerant gas. If you run the air conditioning with little or no gas you will damage the compressor. The refrigerant gas contains the lubricant that keeps the compressor lubricated and running the compressor without gas will not help it to last very long.

I have had experience with mechanics who worked on my airconditioning who obviously did not know as much as they had me believe. I got another guy who only did airconditioning who came to my place and in minutes found the real fault and it was nothing like the mechanic had told me. So there comes a point where you need the opinion of another person especially a guy who specializes in air conditioning as the mechanic you are using obviously is not as good as you have believed. In every service industry there are the good guys who know their stuff and the bad guys who blunder their way through hoping if they replace enough stuff they will find the answer. Just because they are qualified in their field does not mean they are any good at doing the job.

You really are lacking in refrigeration knowledge. There are numerous things that you need to know so that you proceed in the right direction.

First, connect gauge set to the system. If you don't have a gauge set, don't work on a/c. Is there liquid refrigerant in the system? Probably not. So evacuate and see if there is a leak.

If there is a leak, find and fix it. The single most common leak is a compressor shaft seal leak.

No leak? Charge with liquid into the HIGH side with engine off. If all the refrigerant doesn't go in, start the engine and turn the a/c on. Charge the remaining amount by vapor into the LOW side.

You really need some equipment.

Hot wiring the clutch then wasting time fooling around trying to get refrigerant into the system can destroy the compressor.

Refrigerant liquid and vapor circulating through the system moves the lubricating oil around. If there is no refrigerant in the system and you make the compressor turn, what is lubricating it? Nothing!

For your DIY approach, hot wiring the harness to the low pressure switch is something you only do for a few seconds to see if the compressor clutch engages. If you know you have sufficient charge and this is the only way to activate the clutch, then all you need is a new pressure switch.

If there is still refrigerant but just a low charge, this is considered normal slow leakage that would occur over 20 years. The mechanic can confirm your charge is low or non-existent. If just low, get the recharge kit with the Stop Leak additive to restore the seals. Also remember to run A/C once in a while during winters to sling the oil around the compressor and rewet the seals in there.

If the charge was non existent you might need a new accumulator with fresh desiccant inside, but before you recharge you should pump down to hard vacuum and leave it there for a half hour, this will verify no leaks and suck any moisture out of the desiccant making it almost good as new. The mechanic quoted accumulator and O-tube because they are old and refreshing them simply avoids you coming back with complaints in unlikely case they were bad. These parts drive the labor price but don't really need to be changed unless you are changing the compressor and want to keep the warranty on that.

You can clean bugs and leaves out of the condenser yourself, with car wash solution, brush and hose.

Try repressurising it first.

It's a 23 year old car. I would put freon in it myself and see what happens

Best to somewhat understand the vehicles a/c system. 90% of automotive a/c problems are due to a Freon leak. If they a/c Freon becomes to low the compressor will shut off. Also will shut off if too much Freon is added. I would highly suggest have the system vacuumed down. This will help detect a leak and clean out the system. With the age of the system all a/c O-rings should be replaced also the office tube. Go to a reputable shop, reputable shops are less likely to hire shady mechanics and do shady work.

Here are the prices from Rockauto and other local sources if you did the work yourself. I have included the price of a new compressor since you should probably replace that too since your car is so old. Most clogged condensers cannot be cleaned or purged so they must be replaced instead. Your condenser might be okay so replacement may not be necessary. Also, you might want to consider replacing the refrigerant hoses too since they are only $40 on Rockauto.

Receiver/drier - $15.87 rockauto

Condenser - $64.76

Orifice - $0.88 rockauto

Compressor - $112.79 rockauto (good price)

Shipping - $32

PAG 46 refrigerant oil - $7.99 plus tax (oreilly local auto parts)

R-134a - $10 for two cans (walmart)

Sealer - $12 (walmart)

Gramps is right - always get multiple quotes before having work done.

my suggestion - take the vehicle to several other shops and get, if they will do so, a free estimate as to what needs to be done..............then you can compare the work needed + prices............be sure they offer warranties also ( your vehicle is 23 years old and probably has not had the AC serviced )