getting more out of the AC in my 1996 Chevy 1500

[harofreak00]

The AC has always been cool, not cold. For how hots its been the last couple of weeks, I figured I would try and make it cold.

When I hooked up my gauge to the low pressure side, it was showing around 90psi (it was hot out). I added a 12oz can of R134a and it didn't change it.

Dad was over this weekend and suggested that the pump might be on its way out and to change it out.

I picked up a used compressor for $50, $30 in R134a cans, and 8oz of PAC oil for the compressor.

I just swapped it out and filled the system. Exactly the same as before.

The high pressure line is hot, the low pressure line is cool, not cold. The air out of the vents is cool, not cold.

I don't want to drop hundreds of dollars into a $1500 truck by giving it to a pro. Any suggestions?

[Black Pearl]

The evaporator might be plugged. Does it have line driers on it? If so one or both may be plugged. None of your lines are bent are they?

[harofreak00]

Ya it has a dryer. Plugged with what?

No bent lines that I can see.

[Black Pearl]

If you opened up the system, it could have a dirt particle in it. It's happened to us on home HVAC systems. Just a thought. After you replaced the compressor, did you put a vacuum pump on it? That should've pulled out the contaminents and moisture

[harofreak00]

No, dont have a vacuum pump.

Guess I need to bring it to a pro afterall huh?

[Black Pearl]

If nothing else, call one and get thier opinion on it. HVAC and MVAC are extremely similar in nature, they do have slightly different procedures and equipment.

[sandrock]

Vac pumps boil out the moisture and brings the contaminants out, but more needs to be done. Did you replace the orifice tube? That's a small filter located in the AC line, and could get plugged up with debris (read that as chunked aluminum from the compressor).

Here's what I'd do if I could do it all again...open the system, remove both lines from the compressor, add flushing agent and a little compressed air to get it to circulate. Let that set for a few minutes, hours, whatever....an hour should be good. Blow everything out with the compressed air. Remove filter/dryer and toss it. Blow all hoses again, paying close attention to the condensor and the evaporator sides. Put in new orifice tube, filter/dryer, and o-rings. Connect everything, adding the PAG oil as needed. Hook the vac pump to it (You can get air compressor driven pumps at Harbor Freight for around 30 bucks I think), let that sit for an hour or so to pump it down. Once pumped down, make sure the gauges say you still have a vac in the system after letting it set for 15 minutes or so. Once that's verified, charge the system.

Hmmm....do you have an airmix on the truck as well?

[RJolly87]

Few questions. First off, was the pressure tested while the A/C was running, or off?

If running, 90 PSI on the low side is WAY too high. Sweet spot is usually 35-45 psi on the low side. That would indicate a failed compressor, or an overcharged system.

If not running, check it again while running.

[BlackHawk99]

Yes, I agree, 90 PSI is WAYYY too high. It's either very over charged or your coil is plugged. I'm going with the coil being plugged. The truck is 14 years old with a ton of miles.

Open it back up like Brad suggested. In the worst case, you'll be into it for a new (used) coil.

[Jrs3800]

Andrew did you replace the Orifice Tube Filter?

I would have at the least replaced the Orifice tube filter, and the Drier... The compressor you have in it is an HR6 iirc.. And you should use PAG 150 oil I believe..

Low side should generally be in the 30-50 Psi range idling lower temps lower pressure and higher temps higher pressure..

[olblueeyesbonne]

Andrew -Tires Plus in Alexandria does evac and charge for something like $50. Or you can go on ebay and get an evac kit for something like $30. You could offer ac recharges and get your money back on 2-3 jobs.

[wjcollier07]

In addition to what Don & Brad have recommended...

I've learned from talking to the advanced ASE technicians at my shop that pressure readings should only be used in actuality to measure how the system is functioning, high side vs. low side, and should NOT be used to get an anywhere accurate measurement of how much refrigerant is in the system at any given time. The only correct way to fill the system is give it the correct weight the system is supposed to have, after a full recovery and vacuum of at LEAST 15 minutes, if not 30-60 mins.

Another words...take the system apart, flush it out with A/C chemical cleaner to clean out the condenser/evaporator coils as much as possible, flush the system out with compressed air, replace whatever o-rings you can, replace the dryer/orifice tube, and then take the vehicle in to a shop to have a machine automatically do the vac down, weigh the charge, and refill it. This actually will be the most expensive part of it, anywhere from $50-150 depending on where you go...but it's the most comprehensive way for the home mechanic to have it done correctly, and still save the most amount of money when comparing with just charging it with R134a from cans.

But, another $0.02...that low side reading is WAYYYY too high.

[Jrs3800]

I do agree with that John... And the V5 seems to me to be more of a pissy animal to deal with as opposed to the HR6/HD6.... The bad part is that the stealership could get the system no colder than I could and they did it complete for me..LOL...

The pressure are more of a guide, the HR6/HD6 needs to function in a certain range to have good cooling capability, if its outside this range high or low the system will not work properly, as well having an HD6/HR6 Overcharged is one of the worst things you can do..

Just charged a Blazer system to factory speck for the Temps and humidity, and it blew Ice cold... It was 3/4 of a LB low...

I do think his system may be clogged due to the Orifice tube filter, and the system should be flushed to get any debris out of the system, Drier replaced along with the Orifice tube.. If Andrew chooses to tackle this project then he will want to know how many ounces of PAG 150 to install in the drier and the Compressor and or due to the flush may need to know what the system capacity is for the oil charge...

Andrew I suspect Orifice Tube filter may be clogged or the compressor may be bad, both very good possibilities... As well if he doesn't have the tools to do it then I would agree on taking it to a shop to have the system Vac pumped down and recharged..

[crappiefisher]

The 1990 has had this problem forever, low side is 60, high side is around 200-220. Blows cool. The compressor is REALLY tired and probably needs firewall forward attention.

I'm betting that going with a new reciever/dryer and orfice tube, along with a flush, evac and refill, based on weight as suggested will go a long way. You may yet still need another compressor also, and I'm told that ANYTIME a system is opened for any reason, it has to be pulled down to a good deep vacumn for at least 30 minutes to get air and moisture out.

[bonnevilleSSEiman]

also back home in mississippi AutoZone rented out vacuum pumps and a A/C manifold Gauge set ....if there is an AZ in the St. Cloud area you might just rent one....


Advance up their doesn't have one....we don't in elk river either


James