Help with 93 S10 Blazer A/C, trying to retrofit, cycling compressor

rastoma · 06-16-2010, 12:15 PM

Hey all,

I have a 93 S10 Blazer, 96k miles (not 196k), 4.3 V6 (W) engine, 4x4.

I have only had it about 10 months. The a/c didn't work when I got it. The compressor would cycle on and off like it was low on coolant. No difference in air temperature obviously while on. It had not been retrofitted so it had R12.

I haven't tried working on it until recently. I got a professional a/c gauge from Autozone (free loaner) to test the pressure level to see if in fact it was just low coolant. Well, maybe it wasn't something I should have tried to do since I had never measured coolant pressure before but I figured that it couldn't be difficult just to snap on some gauges and read them. The gauges were setup for R134a and came with adapters for the gauges so they could be hooked up to R12 ports. Well they were crap because they 'hooked' on but I didn't know until AFTERWARDS that rubber o-rings were missing from inside the connectors. So all the R12 came spewing out and they ends were 'locked' on and wouldn't come off easily.

I wanted to give that background to let you know that I think all the R12 is now out...... UNINTENTIONALLY.

The compressor stopped cycling after that.

Obviously if you haven't figured out, I haven't had the money to get it worked on professionally, so I thought I would try one more DIY option before saving and taking to the shop. I got a good deal on a retrofit charging system from Interdynamics. 3 cans of air/oil and a trigger gauge with screw-on retrofit connectors.

It says the system is full at 45 psi. Well it showed just about 0 when I hooked the gauge and the a/c was on and compressor not engaging (engine running of course). So I started filling with one of the cans and once pressure got to about 45 psi the compressor started cycling again which I thought was great news that hopefully it's salvageable.

I let it run several minutes but it just kept cycling, on about 1 second, off about 3 seconds. I put a little more and pressure went up to 65 psi and no change in the cycling time. I stopped there.

So, does anyone have any suggestions as to whether this can continue as a DIY project and if so any suggestions on what to do next?

Thanks.

EDIT: I forgot to mention, that while watching the gauge on the LP, when the compressor is on the pressure drops to around 20-25psi and when off the pressure is around 65psi. So when I mentioned above that it's at 65psi, it's at 65psi during the brief time that the compress is OFF. Do I need to keep going and get the psi to 45 while the compressor is ON during the cycling period?

**Raylo** · 06-16-2010, 01:10 PM

I don't even know where to start on this response, except to say a retrofit is a LOT more than just adding the new r-134a. It can be a DIY thing but you need to do a lot more research and learn up on it before attempting. Based on where you seem to be at I'd say get it to a pro before you ruin your compressor.

Wrench97 · 06-16-2010, 01:24 PM

First R12 and 134A are not compatible with each other, nor are the oils they use to lube the compressor, you need to properly evacuate the system and and add pag oil to convert the mineral oil to be compatible with 134a then pull a vacuum on the system to remove any water vapor(from the normal air entering the system) and then recharge with 134a, there is a high side and a low side the low side should be in the mid 40's depending on ambient temps and the high side will run around 150 with the fan running and can go to about 300 before the safety switches shut it down, I suspect you may have had the can on the high side instead of the low side.

rastoma · 06-16-2010, 01:24 PM

Quote:

Originally Posted by Raylo

I don't even know where to start on this response, except to say a retrofit is a LOT more than just adding the new r-134a.

Then how do the tens of thousands of people have success with nothing more than the retrofit kits they buy at the parts store?

I know that doesn't make one an expert in auto a/c, but if the compressor works and there's no leaks, the R134a works.

But if anything I've done up to this point is wrong let me know what I did and I'll take it to someone when I'm able.

rastoma · 06-16-2010, 01:54 PM

Well, looks like the compressor is good hopefully. I determined that the 65psi with the compressor not running was not too high so I put more coolant in and finished the first can. Then shortly after the second can the cycling stopped and the compressor stayed engaged. It took the second can and part of the 3rd can (kit came with 3 cans) when the psi go to 45 while the compressor was engaged. Cool air is coming out but no where near what it should be.

Even if I have to take it to a shop at least hopefully I now know that the whole system won't have to be replaced (crossing fingers).

But the way it is now at least it's bearable to drive in the heat. Also looking forward to having the windshield clear properly on defrost during rain.

rastoma · 06-17-2010, 04:54 AM

Quote:

Originally Posted by wrench97

First R12 and 134A are not compatible with each other, nor are the oils they use to lube the compressor, you need to properly evacuate the system and and add pag oil to convert the mineral oil to be compatible with 134a then pull a vacuum on the system to remove any water vapor(from the normal air entering the system) and then recharge with 134a, there is a high side and a low side the low side should be in the mid 40's depending on ambient temps and the high side will run around 150 with the fan running and can go to about 300 before the safety switches shut it down, I suspect you may have had the can on the high side instead of the low side.

Thank you for the details. I appreciate you and Raylo responding to help.

I definitely had the gauge on the low side. As I have now determined it was just showing a high number when the compressor was NOT engaged and this being the first time I've attempted something like this I did not know that the correct psi range is measured when the compressor is actually engaged.

I do understand what you mean about the oil. I had researched that, thus why I bought the kit from ID (interdynamics). For reference and for what it's worth, it uses ester oil instead of pag oil:

Quote:

Originally Posted by http://www.id-usa.com/how_to_faqs_retrofitting.asp#8

Ester is believed to be better for Retrofit systems because it is compatible with the residual mineral oil left after evacuating a R-12 system.
In addition, Ester oil is a preferred top-off oil because it is compatible with ALL PAG Oils and is much less hygroscopic, which means that it does absorb as much water from the atmosphere as PAG Oils do.

<snip>

Ester Oil, however, is truly universal and will lubricate properly regardless of viscosity.

I also checked out the site Raylo gave and I think I'm going to buy a set of proper gauges and vacuum pump, which I can get for about the price of taking it to a shop and vacuum it myself. It may cost a few dollars more after buying refrigerant again but I get more enjoyment from something if I can learn to do it myself :)

Thank you both again for the correct direction to go in.

**Raylo** · 06-17-2010, 05:57 AM

Looks like you have a better plan now. I would recommend you flush the system to totally remove all traces of the old mineral oil. And don't forget to replace the accumulator. That should be done any/every time the system gets opened and certaily during retrofit since there is a lot of oil left in there. Interesting that the retro kit has ester oil. Most GM r-134a systems use PAG 150. I would also do some research on the low pressure switch. R-134a has slightly different working pressures and temps so you may not have the same cooling performance if you keep the old R-12 LP switch. You could order up one from a 1994 version of that vehicle (which I used to own) and get the R-134 switch. They are cheap. You should also replace the expansion orifice tube whilst in there. They are cheap, too. Also should replace the o-rings. Many sites sell GM o-ring kits that have more than what you wll need.

Good luck. AC work is fun and you can get a good result DIY with a little practice and the right tools.

**Midnight Tech** · 06-17-2010, 06:06 AM

My system shows that both switches were used in that year on the Blazer - NAPA Temp/Murray part number on the 134 one is 207883.

rastoma · 06-17-2010, 08:40 AM

Excellent... thanks to both of u again.

rastoma · 06-17-2010, 08:45 AM

Quote:

Originally Posted by Raylo

Looks like you have a better plan now. I would recommend you flush the system to totally remove all traces of the old mineral oil.

If you just flush the compressor off the car and replace the accumulator, would that be enough?

Wrench97 · 06-17-2010, 10:44 AM

Yes, just don't over fill the oil, too much will cause problems moving the freon around the system.

**Midnight Tech** · 06-17-2010, 11:19 AM

Should be around 8 ounces of oil in the system - most of that hangs out in the accumulator.
If you flush and see a good bit of metal shavings it'd be best to go ahead and do the whole system and replace the orifice tube as well.

**Raylo** · 06-17-2010, 02:38 PM

Here is another LP switch option that allows fine tuning the system. It is actually adjustable with a small screwdriver on the fly as it is operating. This switch controls when the compressor kicks off, which happens more frequently at low a/c load as when most of the refrigerant is in liquid form in the accumulator. Also happens in other operating regimes depending on the balance of vapor and liquid in the system.

The trick to tuning is to set the low pressure setpoint as low as possible without driving the pressure down to where the evaporator goes below freezing. Look at the pressure/temp chart (pressure read from low side gage) for that and/or look for frost formation. If that happens your evap will become a block of ice as the condensation on it freezes instead of running off, and can get so bad that air won't even come out of your vents. Tweak the switch accordingly. But the bottom line is this switch is easily adjustable and will work with r-134 and 12 systems... and allow some tuning.

http://www.omega-usa.com/AC-Part/29-30400.html

Also, FYI, the system label plate on S10 4.3L R-134a systems of that vintage called for 30 oz of R-134a, IIRC. Probably a pretty good number for the retrofit.

rastoma · 06-17-2010, 02:46 PM

Great, thanks.

**kjms1** · 06-17-2010, 10:04 PM

you need to change the orifice also a $10 part

you should also remove the compressor and drain the oil out of it and flush the condenser good ... only use ac flush

add 8 oz of pag oil 2 for accumulator 2 for condenser & 4 for compressor

make sure you give it a good evacuation with the system being open a long time

**Raylo** · 06-18-2010, 05:56 AM

Here is the DIY flush tool I use. Works great.

https://www.ackits.com/pc/91046-A/Fl...l+AC+Flush+Kit

**Midnight Tech** · 06-18-2010, 08:26 AM

Agreed Raylo - Mastercool has a good line of A/C tools that are also a good value.
Also, there are two kinds of flush - one that is an oil base and one that is not. All the A/C guys I deal with including the manufactuers reps advise using the non-oil type. The other one will actually trap and hold contaminents in the system and not remove them.

rastoma · 06-18-2010, 09:24 AM

Quote:

Originally Posted by Raylo

Here is the DIY flush tool I use. Works great.

https://www.ackits.com/pc/91046-A/Fl...l+AC+Flush+Kit

This might be a dumb question, but is that the 'flush solution' in the can or just the propellant to force cleaning solution through the system? How do I know if it's the oil or oil-less type?

Is one can enough to do the job of what you all have suggested needs to be done?

EDIT: never mind, I found the instructions on it's use on another site. You fill it and pressurize it with air :)

**Raylo** · 06-18-2010, 10:49 AM

You got it. You can buy the flush solvent solution in quarts or gallons on the same site. A quart should be enough to do your system since you didn't have a compressor failure and should be fairly clean.

fourmiles · 06-06-2011, 04:10 PM

Raylo: I was impressed with your knowledge until I saw you are a Gator fan. BOO! GO DAWGS! Just the same, I need help. My '94 Blazer was fitted with the R134a system but the compressor went bad. I got a junkyard compressor but before I install it can I check it somehow? Also, before I remove the 'bad' one, is there some way to test it to make sure that is indeed the bad part?