TorchTarga94

Having some issues with my A/C (of course, I am 300 miles from home with the car on vacation). Everything seems to work fine. Fan speed goes up or down with every button press as it should. The air is ice cold and spits out ice cubes. Everything works perfectly, then after an hour or so of driving its like the vents shut off and you hear the blower motor get louder (almost like the blend door is shut and the air has no where to go, if that makes sense?) If I play with the settings for a while, direct the air to the floor, defrost, and then back to auto or recirculate I can usually get it to come back. Then about a half hour later of driving and the vents get weak again. Here is what I have already done:

1. I have replaced the vacuum valve under the passenger side fuel rail cover that directs vacuum to the A/C and Cruise (I thought this actually fixed my issue but apparently not). It was $3.00 and worth a try.

2. Back in January I crawled under the driver side dash and actually removed the programmer. Confirmed everything looked okay upon inspection and the "nipples" on the programmer box weren't pliable or pinched so I don't think they are collapsing under vacuum like some of the other threads on here suggest (but maybe there is an issue there if it controls the blend door?)

When the main dash vents stop blowing hard there is still a little flow. There is also some light flow out of the defrost and floor but like i said, it is very minimal and the blower motor sounds like it is pushing air with no where to go. It is just weird if I play with the settings on the head unit I can usually get it back. Not sure if I should remove the control head and try to clean the contacts next? The control head isn't showing any codes.

Any help or ideas is greatly appreciated. I would like to tackle this issue when I get back at my house. Miserable weather is just around the corner and so is more road trips.


Patrick

PatternDayTrader

Sounds like the evaporator core is freezing up.
When you turn the ac off for a few minutes then it thaws out and will resume working again.
Step one is verify the proper refrigerant charge. That is probably the only issue. If that is not the problem then there's probably an issue with the orifice tube.
Finally, any moisture in the system can do weird things if it freezes up around the orifice tube or in the evap core.

TorchTarga94

So forgive my HVAC stupidity, but how do I go about further diagnosing that or alleviating that issue? When I park the car there is a ton of condensation that leaks out of the drains. Enough to cover the garage floor.

PatternDayTrader

Yes I bet there is. The entire evap core is turning into a giant block of ice, and thats why air won't blow through it and out the vents.





BTW .... That's not HVAC stupidity. You are suffering from a somewhat unusual problem.

TorchTarga94

It's just weird that I can get it back after I play with the buttons for a little bit. But what you are saying sounds plausible and aligns with what is happening. Would keeping the air temp on a higher setting, say 68-72 help alleviate the issue of the evap core freezing up?

PatternDayTrader

No. In fact it might make it worse since the air passing through the evap core (before it freezes) will be somewhat restricted by the temp blend door. This will result in less air flowing across the evap core allowing it to freeze sooner.

TorchTarga94

Makes sense. I appreciate the help. So your suggestion is to confirm the refrigerant levels are correct and go from there? How about the drier/accumulator? It looks like a "block of ice" sometimes Do these have a certain life expectancy?

PatternDayTrader

Keep me posted on this since my car is suffering from a similar problem, so I will be very interested in what you find out. Unfortunately for me, mine is much more serious since the lines themselves after the evap core are freezing on the outside. To the point where I have a very thick coating of ice on the receiver/dryer and all the low side lines. Also my evap core wont freeze up. In fact it doesn't really even get all that cold. On mine, all the evaporation seems to be occurring in the low side lines instead of the evap core. Anyway I think my orfice tube has come apart or my evap core is internally damaged. Eventually ill fix it but I haven't gotten around to it yet.

PatternDayTrader

!!! .... I was posting a reply at the same time you were posting this. Yes start by confirming the proper refrigerant charge. Don't worry abut the receiver/dryer. It will last forever unless it get a hole in it.

PatternDayTrader

Maybe someone else has run into this. Now I'm thinking this may be much more common than I thought.

TorchTarga94

Check out this thread on an S10 Forum, sounds very similar to what we may be experiencing:

http://www.s10forum.com/forum/f299/a...g-hard-497342/

PatternDayTrader

Yes hell yes ..... I suppose one of us needs to verify that the low side switch's actually are intended to cycle the compressor as opposed to just protecting the compressor if the refrigerant charge gets too low. Not every system cycles the compressor, some systems the compressor just runs. Where is WVZR and his service manuals ....

If its just the low side switch then this will be a very cheap and easy fix.... Like thirty bucks and 5 minutes labor.

PatternDayTrader

I knew this forum would pay off for me at some point ..... How coincidental it seems to have come from a quadracer ....

PatternDayTrader

Ok so the one guy in the s10 thread is talking about the receiver/drier becoming saturated with moisture and ultimately needing replacement. I dont agree with that at all. He is overlooking what happens when you properly recover refrigerant and evacuate the system with a vacuum pump. The moisture goes with it. Especially if you run the car with the vacuum applied to the system and allow engine heat to warm everything up. The only reason you would need to replace the drier would be if your sort of just scab jobbing it together and not properly evacuating the system.

TorchTarga94

Cliff Harris

I had similar symptoms and the AC guy said my system was overcharged.

PatternDayTrader

Its pretty difficult to see how overcharging could cause the low side to freeze up. You wont have the pressure drop across the evap core that would be necessary. However this is a distinction without a difference, since the fix is identical to an undercharge. What we really need to know is if the low side switch is responsible for cycling the compressor or if its just to protect the compressor in the event pressure gets to low. I suppose an over charge might actually prevent the low side from dropping low enough to open the switch, and possibly leading to freeze up .... That would make sense. Either way step one is verify the proper charge.

TorchTarga94

Update:

Drove home yesterday. I put a little over 700 miles on the car round trip. Here is a recap:

-Thursday night drove to Saint Augustine (3-1/2 hour drive from Tampa area), about an hour and a half into the drive the A/C Froze up and barely blew cold air. I fiddled with the buttons for a while and got the A/C back in 10 minutes or so and was good for the rest of the drive there. The temp was on 60 and the re-circulation button was on.

-Friday morning drove to Jekyll Island, GA from St Augustine (1-1/2 to 2 hour drive from St.Aug) the A/C froze up and about an hour into the trip going to Jekyll and coming back to Saint Augustine. Temp was on 60 and the re-circulation button was on.

-Sunday morning drove back home from Saint Augustine. This time I kept the inside air temp above 65 degrees (kept it at 68 the whole way) and never touched the recirculate button. I kept it on the "head & feet" selection. The A/C never froze up the entire way back home. The ambient air temp was approximately 92 degrees for most of the drive and it was mostly highway and interstate.

Theory: I was just plain working the A/C to hard. This in conjunction with keeping the air on recirculate really did freeze up the evap core. By not using the recirculation button on the way home and using hot outside air seemed to remedy the issue. I am still going to get the refrigerant levels checked as Amotoxracer suggested, but I think I may be good. With the temp on 68 and the "head & feet" selection we were both comfortable the entire way home even with as hot as it was. There may still be an underlying issue, but just a thought. I think putting the air on 60 and using the recirculation button to get cooled off quickly and then switching over to the "head & feet" selection might work perfectly for long drives.

Also, I was still scavenging the internet the past couple of nights and stumped upon a Chevy Sonic forum where a guy said his service advisor told him to not run the air below 65 degrees for more than 25 minutes at a time or the evap core can freeze over, he went on to say this is especially true on extended drives. He also suggested to only use the recirculate button when needed (behind a large semi blowing black smoke, driving by a dump, etc...) Leaving the recirculate button on and the temp below 65 can cause the evap core to freeze over (according to them).


Will keep this thread updated if I come across anything else.

antfarmer2

If you constantly run any ac to a unattainable temperature it will freeze up.

jsmn4vu

It's very common for people to set an unattainable temperature thinking it will cool things down faster. It doesn't. If your goal is 70 degrees inside the car, that temperature will be reached as quickly with the dial set on 70 as it will set on 40.