Thread: OT: Car AC problems, advice needed!

I have a 99 s10 pickup that I mainly use for hauling stuff around, normally I'll drive my car since it gets a lot better gas mileage. Until recently I've been able to deal with the air in the s10 not working on the odd occasion that I drive it, but it's getting real hot here now and I can't stand driving it anywhere anymore. I don't really care to bring it to anyone to fix it, especially since I know I can. I'd just like some advice on my assumptions since I don't know AC units that well.

I do know the S10 has a compressor setup that runs continuously, it should not cycle on or off while in use. I also know that my system uses an orifice tube for expansion, I don't think there is an actual expansion valve anywhere.

The compressor cycles on as it should and continuously runs. While running I can see pressure within operating range on the low side. When I cycle the compressor off the pressure on the low side will settle, so I assume the compressor is doing something.

No lines under the hood sweat, everything is around the same temperature. I went to try to add a bit of refrigerant, but according to the gauge on the kit I bought my pressure on the low side is already at the upper limit for the current ambient temp so I didn't add any more. I bought the truck like that, so I assume there are no leaks anywhere.

My blend door does work, I can switch from hot air to warm air using nothing but the temperature knob. The s10 only has one blend door as far as I know, if there is a second one I have no idea where it could be hiding.

So, without a high side gauge I'm assuming that my orifice tube is likely clogged or worn out. I would assume that I would see a super low pressure or even a vacuum on the low side if it was clogged though, is it possible to see the right low side pressure with a fully charged system with a clogged orifice tube?

I don't think it's the dryer, if I somehow had water in the system clogging things up I would expect the system to blow at least a little cold before going back warm but that's not the case. I also don't think it's anything electrical, as the compressor cycles like it should, no faulty pressure switches interfering with anything. I don't really know the symptoms of a bad accumulator, but I would assume such a thing could only clog. Regardless, the dryer and accumulator are one unit on this truck so I will probably be replacing them with the orifice tube.

Anyway, does anyone have any advice or tips before I start replacing things?

When I had a similar problem it turned out to be a family of field mice nesting in the air filter, blocking the flow.

They looked so cute in there I hated to evict them. But I did.

My Dodge had A/C had not worked for a year, finally took it in last week... Hooked it to a machine and told me it had a full charge, but the orfice was plugged. He was able to backflush and get it working. Charged me 120 dollars, (used 4 lbs refrigerant). A/C is better and colder than it was new..

Originally Posted by Sea Farmer

When I had a similar problem it turned out to be a family of field mice nesting in the air filter, blocking the flow.

They looked so cute in there I hated to evict them. But I did.

I never really considered that, but when I bought the truck neither the heat or AC worked. A back flush of the heater core got the heat going like a champ, so I don't think I have anything clogging that side of the system up. Worth taking a look though, thanks!

Originally Posted by Davis In SC

My Dodge had A/C had not worked for a year, finally took it in last week... Hooked it to a machine and told me it had a full charge, but the orfice was plugged. He was able to backflush and get it working. Charged me 120 dollars, (used 4 lbs refrigerant). A/C is better and colder than it was new..

I didn't know it was possible to back flush a orifice tube, do you know anything about the process at all? I would assume that you would need special tools to keep air out of the system while doing that.

An orifice tube is less than 10 bucks, and a dryer/accumulator is only around $30. A full charge of refrigerant and oil is less than $60. If I can find someone to just back flush it for $120 I may just do that!

Do you know if your compressor cycled when the orifice tube was clogged?

Sounds to me like they discharged the system, flushed it out, then recharged it. That's why they used 4 lbs of refrigerant

You really should just take it in to a qualified auto a/c tech. Replacing any of those components will require a vacuum pump and freon, releasing your old freon into the atmosphere is probably even illegal now. Having all of the info., ambient temps., output temps, high and low pressures and knowing what they are as well as knowing how to interpret those specs is more than most of us know and worth paying for that experience, when the alternative might be frustration and repeated freon dumps along with just throwing parts at the problem. Anyway thats just my opinion, good luck with whatever you decide.
Ron

Mike- I don't know Jack S. about automotive AC but I do reefer vans all day and except for orifice/TXV I think they're pretty similar. From description I'd say you have a leak and noncondensibles in the system. You need a vacuum pump, gauges and micron gauge. I don't know about plugged orifice but if it is, obviously leak! Always some oily mess around a leak but under the hood might be tough. Backflush whatever that means would be short term, the leak has to be found and fixed.
The filter drier changed between evacs to 500 micron and recharge is how I'd go at it after fixing the leak.
Good luck,
John

Originally Posted by Porschefix

You really should just take it in to a qualified auto a/c tech. Replacing any of those components will require a vacuum pump and freon, releasing your old freon into the atmosphere is probably even illegal now. Having all of the info., ambient temps., output temps, high and low pressures and knowing what they are as well as knowing how to interpret those specs is more than most of us know and worth paying for that experience, when the alternative might be frustration and repeated freon dumps along with just throwing parts at the problem. Anyway thats just my opinion, good luck with whatever you decide.
Ron

I agree with Proschefix - by the time you by a take it to a shop to properly evacuate the freon (Cheapest I've seen the freon reclamation units is around $600), buy your own vacuum pump, gauges, freon, PAG Oil, etc (btw the best way to add in the correct amount of freon is by weight, thus you'll need a scale. Though you can get by w/o one) it may be cheaper to take it into an A/C shop. Plus if they screw it up, you can take it back and complain

You said that the compressor is continuous run? It must have a veriable displacement compressor and it may not be shifting because of blockage in the high side.Most car systems have a low pressure cut off switch so unless it has been jumped the compressor wouldn't run if you had no pressure.I am sure a Haynes or Chilton manual would explain the system in detail.I've been out of the automotive business for a long time,so maybe they don't use low pressure switches any more?
Randy

I took my Ford pickup to a professional shop to install a new compressor, accumulator, and orifice tube last year. They failed to flush the old oil out of the system and it ruined that new compressor within a few days.
Since then I've bought the tools and will do this round myself.

Originally Posted by wb2vsj

I agree with Proschefix - by the time you by a take it to a shop to properly evacuate the freon (Cheapest I've seen the freon reclamation units is around $600), buy your own vacuum pump, gauges, freon, PAG Oil, etc (btw the best way to add in the correct amount of freon is by weight, thus you'll need a scale. Though you can get by w/o one) it may be cheaper to take it into an A/C shop. Plus if they screw it up, you can take it back and complain

That's no fun.


How do you collect tools and find an excuse to buy them then?

Originally Posted by Mike_

I do know the S10 has a compressor setup that runs continuously, it should not cycle on or off while in use. I also know that my system uses an orifice tube for expansion, I don't think there is an actual expansion valve anywhere.

You have a CCOT (Cycling Clutch Orifice Tube) system. The compressor is cycled by a pressure switch: when the pressure is low, the compressor comes on, when the pressure gets high enough, the compressor stops. The Freon is continuously bled thru the orifice tube; excess freon is stored in the accumulator upstream of the orifice tube. A very simple system. From your symptoms, I'd say you don't have enough Freon in the system. Take it to a professional A/C shop and let them fix it.

I'll tell you what works for me:

1. Open window.

2. Let hot air out.

3. Problem solved.

I can't imagine wasting a beautiful 90 degree day cowering inside a refrigerator.

watch youtube videos on how to service a/c, your system should have 45 to 55lbs on the low side with the system running at full blast in summer. your one can low is my guess. Go barrow a gauge set and check it. you can get a buy a vacuum pump on craigslist for a 100 bucks , buy the tools , learn something, and do it yourself. DONT use a leak sealer freon it clogs the system. I like to use leak dye (12 bucks) and a black light to find my leak first then open the system fix it once and add a dryer and orifice tube . If your dont change eva, compressor, condenser then no oil is needed.

Until you get a high side gauge on it and post that reading also, everyone here is just guessing. If you do have to open it up definitely replace the orifice tube, and vacuum down the system before recharging.
James

Originally Posted by sa100

I'll tell you what works for me:

1. Open window.

2. Let hot air out.

3. Problem solved.

I can't imagine wasting a beautiful 90 degree day cowering inside a refrigerator.

That would be great, except the 90 degrees is almost our night time temperature out here. Much of Kansas (and all the Great Plains) has been hotter than Death Valley this week. At 115, being able to cower inside a refrigerator can be a matter of life or death.

Originally Posted by Monomer

That's no fun.


How do you collect tools and find an excuse to buy them then?

Opps - yeah, you got me there

Originally Posted by Rex TX

Sounds to me like they discharged the system, flushed it out, then recharged it. That's why they used 4 lbs of refrigerant

I didn't catch that, I guess 4 pounds is a lot of freon when it comes down to it. The cans I have are 16oz I think. I just looked up the s10 full charge spec, and apparently it's only 1lb 14oz and 3oz of oil. Vans must have bigger AC systems or something.

Originally Posted by Porschefix

You really should just take it in to a qualified auto a/c tech. Replacing any of those components will require a vacuum pump and freon, releasing your old freon into the atmosphere is probably even illegal now. Having all of the info., ambient temps., output temps, high and low pressures and knowing what they are as well as knowing how to interpret those specs is more than most of us know and worth paying for that experience, when the alternative might be frustration and repeated freon dumps along with just throwing parts at the problem. Anyway thats just my opinion, good luck with whatever you decide.
Ron

I can rent a venturi vacuum pump from the auto parts store, with the screw compressor at work I doubt I'd have a problem pulling enough of a vacuum on the system. I don't really see it as not worth learning about and just paying to fix it, in fact most times I'd rather buy a new tool and teach myself something new. If I need to figure out temp to pressure ratios and output temps so be it, it's really not all that complicated when it comes down to it. Besides, it's not my first time fixing AC systems in a car before. I like it when the compressor just shells itself or locks up though, so much easier to diagnose and fix!

Originally Posted by jmead

Mike- I don't know Jack S. about automotive AC but I do reefer vans all day and except for orifice/TXV I think they're pretty similar. From description I'd say you have a leak and noncondensibles in the system. You need a vacuum pump, gauges and micron gauge. I don't know about plugged orifice but if it is, obviously leak! Always some oily mess around a leak but under the hood might be tough. Backflush whatever that means would be short term, the leak has to be found and fixed.
The filter drier changed between evacs to 500 micron and recharge is how I'd go at it after fixing the leak.
Good luck,
John

If I had a leak I don't think it would hold the 45 or so PSI it does for as long as it has. It's holding about 45 at 80 or so degrees, which I actually believe is a little on the high side. A plugged orifice tube doesn't necessarily mean a leak is somewhere, at least I don't think so. I was thinking more along the line of the dryer dissident bag exploding and clogging the orifice tube, restricting expansion and keeping anything from phase changing like it should. I'm borrowing a high side gauge from a buddy at work and renting a venturi vacuum pump from the auto parts store, but what is this micron gauge for? Is it used to measure the condition of the refrigerant or something?

Originally Posted by wb2vsj

I agree with Proschefix - by the time you by a take it to a shop to properly evacuate the freon (Cheapest I've seen the freon reclamation units is around $600), buy your own vacuum pump, gauges, freon, PAG Oil, etc (btw the best way to add in the correct amount of freon is by weight, thus you'll need a scale. Though you can get by w/o one) it may be cheaper to take it into an A/C shop. Plus if they screw it up, you can take it back and complain

I've got most of those things, either borrowed or my own. I'd never heard of adding oil by weight though, I do have a small gram scale if I need to add oil though. I don't have the reclaim unit though...

I'm not entirely sure what shops you are taking your car to, but it seems like every time I do they make the problem worse and then play dumb until I'm forced to file a small claims case or a chargeback!

Originally Posted by ratbldr427

You said that the compressor is continuous run? It must have a veriable displacement compressor and it may not be shifting because of blockage in the high side.Most car systems have a low pressure cut off switch so unless it has been jumped the compressor wouldn't run if you had no pressure.I am sure a Haynes or Chilton manual would explain the system in detail.I've been out of the automotive business for a long time,so maybe they don't use low pressure switches any more?
Randy

Yep, either 98 or 99+ s10's switched to variable displacement (da-5, I think) compressors. I can see the low side pressure climb when I turn the compressor off, and I see it drop when I switch it back on. I'm not sure if it's working like it should but it does seem to be doing something. I think the low pressure cut switch is normally 20PSI, but I never see the pressure drop below that. I have shorted low and high side switches to see if I could hear the compressor shift or anything, but I can't hear any changes nor do I ever get cold air. I have both a Haynes and Chilton manual for the truck, but they are both rather vague when it comes to diagnosing AC stuff. They are good for finding all the temperature and pressure switches though.

Originally Posted by Rex TX

I took my Ford pickup to a professional shop to install a new compressor, accumulator, and orifice tube last year. They failed to flush the old oil out of the system and it ruined that new compressor within a few days.
Since then I've bought the tools and will do this round myself.

That's exactly what I'm worried about! Nobody will ever work on your own stuff as good as you will.

Originally Posted by Monomer

That's no fun.


How do you collect tools and find an excuse to buy them then?

Exactly! Not to mention the experience you gain along the way. Maybe next time one of the spindle coolers on our mills goes down I can fix it instead of calling for help. Gotta start somewhere, or you'll always be paying someone else.

Originally Posted by 310 Guy

You have a CCOT (Cycling Clutch Orifice Tube) system. The compressor is cycled by a pressure switch: when the pressure is low, the compressor comes on, when the pressure gets high enough, the compressor stops. The Freon is continuously bled thru the orifice tube; excess freon is stored in the accumulator upstream of the orifice tube. A very simple system. From your symptoms, I'd say you don't have enough Freon in the system. Take it to a professional A/C shop and let them fix it.

Almost certain I don't. The compressor runs continuously, the clutch shifts in when you turn the knob to AC and it stays in until you turn it off. My 2002 Blazer was this way as well. Pre 98-99 s10's do have cycling clutch systems though.

Originally Posted by sa100

I'll tell you what works for me:

1. Open window.

2. Let hot air out.

3. Problem solved.

I can't imagine wasting a beautiful 90 degree day cowering inside a refrigerator.

Cute! But you've obviously never been to Kansas in the summertime. If you can stand driving my black truck with black interior in the city where speed limits are less than 45 without almost dehydrating you can have the thing!

Originally Posted by vettepicking

watch youtube videos on how to service a/c, your system should have 45 to 55lbs on the low side with the system running at full blast in summer. your one can low is my guess. Go barrow a gauge set and check it. you can get a buy a vacuum pump on craigslist for a 100 bucks , buy the tools , learn something, and do it yourself. DONT use a leak sealer freon it clogs the system. I like to use leak dye (12 bucks) and a black light to find my leak first then open the system fix it once and add a dryer and orifice tube . If your dont change eva, compressor, condenser then no oil is needed.

I started with a can of UV leak dye, figuring that the system just had a leak. I used one of those crappy low side filler gauge things and saw a median pressure range for the ambient temp, so I skipped the leak dye and added a bit of refrigerant until I was on the high limit of what was recommended for the present ambient temp with no noticeable change, do you think I should try adding more? I didn't want to keep going and hit the high limit switch and have to figure out how to get just a little bit of refrigerant back out.

Autozone rents venturi vacuum pumps, it's what I used when I replaced the compressor in my girl's van last year. Was noisy as hell, but worked like a champ. I should have a high side gauge to borrow this afternoon hopefully, I just hope it's the quick connect style and not the old thread on one.

I was also going to try draining as much oil as possible and replacing what I could with a like sized amount. Do you think that would be necessary since I won't be touching any of those components?

Originally Posted by J. Randall

Until you get a high side gauge on it and post that reading also, everyone here is just guessing. If you do have to open it up definitely replace the orifice tube, and vacuum down the system before recharging.
James

Yeah, I really do need to check that side. I'm expecting to see about double the ambient temperature, is that about right?

Originally Posted by gbent

That would be great, except the 90 degrees is almost our night time temperature out here. Much of Kansas (and all the Great Plains) has been hotter than Death Valley this week. At 115, being able to cower inside a refrigerator can be a matter of life or death.

Someone who understands! Windows work fine till around 90 degrees. But this Kansas weather is HOT! Riding a bike down the highway is like riding face first into a hair dryer...

Originally Posted by Mike_

Someone who understands! Windows work fine till around 90 degrees. But this Kansas weather is HOT! Riding a bike down the highway is like riding face first into a hair dryer...

Some one has to grow all that corn..... I guess that's you....

why not get in your airconditioned corn picker ?

ok...so it's not harvest time yet... got a/c in the tractor?

Comparing a piece of open farm equipment to an enclosed car sitting in a concrete jungle surrounded by a bunch of other cars putting off heat. Sounds about right.

There are air conditioned corn pickers and tractors too, Not that I've ever touched either in my life. I do work right next to a John Deere dealership, and I'd say that 99.9% of the stuff they have out there has AC. Want a pic for proof?

How dare I want to be comfortable, the nerve!