Burb AC question

[markelectric]

On the 99 Burb the AC seems to take forever to get cold comming out or under the dash. The rear seems to be real cool real quick. The kids are freezing and we are sweating for a while. Eventually it will cool down some but never as cool as the rear.

[Robyn]

System is a little low on refrigerant.

The back one is hogging all the flow and leaving the front one without enough flow.
The rear AC uses an expansion valve while the front uses an orfice tube.
The tube must see liquid passing through or you get little to no cooling. Use a parts store add a can unit and bleed in a little at a time though the low side fitting. (Cold) until the unit up front blows cold. You should hook up a set of gauges but you can w.a.g it and get close enough. (A/C must be running to add 134a)
When the refrigerant fill is correct both should blow ice cold.

Good luck

Robyn

[markelectric]

Shows how much I know about AC. I would assume that if it was low both would have diminished the same amount. I guess I will put a can in it and see what happens. The hose kit I have is one of those cheapies with a guage so I will be able to watch the pressure. THANKS!!

[Robyn]

The rear one has the expansion valve and when the rear fan is activated the valve will allow flow and this deprives the front unit of liquid.

My Burb was the same way after I recharged the system and I had to go back and add a bit more.
I dont have a scale to weigh the 134 into the sytem so I just watch the pressures and when its good and cold and the clutch is cycling about right I call it good.
I KNOW its not the best way but I have done these this way for years and never had one lick of trouble. Just dont over charge the beast. That can stall the compressor and cause hate and discontent as your serp belt fries to a cinder. :eek:

[HammerWerf]

Mark,

An observation from my 99 Suburban. We had to replace the compressor last year. So, we think the charge is close to correct.

Here is what we have seen both prior to and after the compressor changeout.

Even on hot days around where we live, >100F, if the trip is reasonably long, the kids complain that they are getting cold. Like you, we're still sweating. The windows in the rear doors and back are tinted very dark. the front windows are quite clear, as per CHP requirements. We think that the dark tinting is preventing most of the heat from penetrating the cab in the back, and the rear evap unit is doing a very good job. The front allows the infrared to come in and keep us warm. With out the infrared to keep warming up the inside, the kids get cold. During this summer, while on vacation, I had to turn up the heat to keep the kids from going into suspended animation.

We also were able to ice over the evaporators regularly during the trip.

HammerWerf

[JohnC]

We also were able to ice over the evaporators regularly during the trip.


Low side pressure is too low.

[markelectric]

The difference in the air temp exiting the front vents is much warmer than the air coming out of the upper rear vents. I am going to check the charge when I get a chance.

[Robyn]

On a 90 F day my DaHooooley will blow air out the front vents at between 37-41 degrees depending on how I am traveling. slow slogging in traffic and it will warm some, say maybe to 45.
Long periods of idleing will cause it to warm more due to a lack of airflow over the coils out front.

Hope this helps

Robyn

[DA BIG ONE]

Some time ago I had an AC problem, turns out the AC required much more of a R-134a charge after filter/dryer change out and both ac's must be set to high. Note:filter dryer was same size as one replaced. However, stickers for filter/dryer have correct updated charge data.

Over charge units & the ac will be real cold when first used but excessive pressure will shut system down.

[Robyn]

Oh yeah
Been there done that. :D

Sometimes compressor will even stall out if you get too much charge in the thing.

The best way is to weigh the charge going in on a dry system.
Unfortunately this is not possible when you are doing a partial charge.

Once you start seeing good gauge readings things should pop right into good order.

[cshade]

I had the same problem with a cold cold rear a/c and a barely below ambient front. A re-chage helped a touch, but a new compressor was ultimately the answer. It's amazing what several hundred bucks can do for a car...


--Charles