Is adding r-134 coolant for my a/c easy to do for a novice? It was charged 2 yrs ago for $150 ($75 for charge, $75 to check for leak). At that point they checked for a leak in the system and found none. I'd rather not pay another $150 if this is something I can do on my own. Thoughts/suggestions? Thanks, John

 

Easy to ADD on your own. More difficult to figure out whether adding is the right thing to do.

Check out about renting/borrowing a gauge set. You want to measure both high & low side pressures while it's running, check against what they SHOULD be based on the outside air temperature.

Look in the sticky thread (ONLINE MANUALS) for a repair manual covering your car. I bet it has details about what to measure.

 

Thanks JimBlake. I will check out sticky thread. I found a 10 step process on the web. It didn't mention anything about checking the high pressure side, just the low (while the car was running.) Thanks again.

 

Measuring both really gives you a more complete story of what's going on.

Obstruction in the system combined with some misguided mechanic who just added refrigerant; can result in the low pressure being sorta OK while the high pressure is too high & the cooling power is wimpy. If enough extra is added, the high-pressure safety cutoff can just switch the system off.

I'm not really much of an AC guru, but there's a couple people on here who are - hope they chime in.

I'm gonna move this to General Tech, where you'll probably get more people looking at it.

 

Even pro's acknowledge that only way to charge precisely is to remove all charge and charge by weight into empty system.

I have charged by pressure using following approximate procedure. Doors & windows closed, car in shade, engine at 1500 rpm, max AC, max fan. Measure air temp entering condensor and air temp from center vents. Allow system to stabilize for 10 minutes. Add charge slowly until high side is approximately 2.5*ambient air temp entering condensor (100F~=250 psi). Key word is approximate, as I've had both lower and higher high side pressures. Low side should go down to about 25 psi minimum when compressor is engaged, until compressor cuts off, and then rise to about 45 psi when compressor will re-engage. Vent exit temps should be about 40-50F, depending on humidity and ambient air temp. Look for about a 35 degF pulldown across evaporator(80F cabin interior => 45F vent exit temp).

Honda shop manuals have a complex chart describing system pressures for varying humidity and ambient air temps. It uses similar procedure, but doors and windows are open.

That said, there must be millions who have charged w/ a Walmart special and got away w/ it. No way to know if you're charged correctly, but you may get lucky and there's a significant margin of error where acceptable cooling is possible.

good luck