Credit: davey6693

Just successfully overhauled my a/c – report (long)

I think I’m one of the few people that have done this, so I’ll post my findings here. In short, a/c repair IS possible if you do some research, take a little care with O-ring connections and buy a set of pressure gauges. I saved myself 600 dollars and I now have a set of gauges and a vacuum pump for any work on future cars. If you can rent a vacuum pump or get a garage to do the vacuum/recharge you can save more in the short term.

Here’s how I got my ice-cold air back

1. Bought a set of gauges and did some research at and These are excellent boards with a/c service professionals making daily contributions. The gauges I bought from the tool warehouse.

2. Found that my low side pressure was too high and my high side pressure was too low. Diagnosis: shot compressor. This was fairly easy because it was starting to make noise and get worse with time.

3. Unfortunately a dead compressor can spew metal parts around other components (black death). In my case I couldn’t just replace the compressor because that crud can cycle around to the new compressor and kill it very quickly. Our condensers are parallel flow condensers, so flushing often fails. I decided to replace it.

4. At this point I had a choice to make – get an a/c shop to vacuum and recharge my system or buy a vacuum pump. They can apparently be rented too but I couldn’t find any in my area. I figured why not pick one up, it’ll serve me well for years. Got some vacuum pump oil and a pump from the tool warehouse.

5. As an expansion valve is only 45 bucks, I picked up one of those too. O-rings are important to prevent leaks, and should be replaced whenever a system is opened up. My shopping list was now:
compressor, dryer, expansion valve (all from Carlisle Auto Air).
condenser, o-rings, compressor oil, nylog (an excellent o-ring conditioner that minimises leaks) and flush solvent (all from

6. The whole job took about 10 hours, but it’s pretty straightforward.

a) Add six ounces of oil to the compressor and 2.5 to the dryer (do the dryer bit right at the end).
b) Undo the drivebelt and bolt on the new compressor.
c) Drain coolant, remove radiator and install condenser.
d) Expansion valve was the trickiest – remove glove box (six screws), unbolt refrigerant lines near the firewall (two bolts), remove evaporator housing (four screws), open up evaporator case (six screws), remove old expansion valve (three bolts and a bit of tape). At this point I added flush solvent to the evaporator and blew some compressed air through it. Then I replaced the expansion valve.
d) Replace dryer last it’s good to keep it sealed until it’s needed so that the dessicant bag doesn’t get saturated with moisture).

7. When each pipe between components was unhooked at both ends, I poured in some flush solvent and blew compressed air through to clean them out. One of the tubes is long and most of the others are pretty short so it wasn’t much of a big deal. O-rings were replaced and covered in a thin layer of nylog as I went along.

8. Vacuumed system down for an hour, added a bit of refrigerant and watched the pressure gauges for 20 minutes. No leaks, so continued to fill until almost two cans of 12 oz refrigerant (1.4 lbs) had been added. Air was cold, job done!

This probably looks long, and in some ways it is. But some of you guys do much more complicated stuff than this. One thing I don’t like is being told by mechanics to never touch my a/c because it’s “complicated” or “beyond the DIYer”. The truth is it’s a pump, valve, two heat exchangers and a dryer, and no-one should be scared about doing work on it. I would say if you’re serious about it, buy a set of gauges for 60 bucks. If you don’t want to buy the gauges, then it’s probably not for you.

The old saying of “Do it right, do it once” definitely applies, but providing you do some research and don’t cut corners you’ll be fine and can save a lot of money.


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