AC problems

[CROOZ1N]

First of all the system was converted last summer to r134a. Everything was flushed and cleaned out . All the hoses removed and flushed. New Variable out orifice put in and re-man compressor. Everything was working ok till the clutch went out 400 miles from home. This in turn caused a loss of the serpentine belt etc.
We couldn't get a compressor or clutch over the weekend I was there and had to get back to work on Monday.
I was able to find a used compressor from a fairly reliable source.(Gordon Killebrew) and that allowed me to get the Vette home. I pulled a good vac on the system recharged it and thought it was cooling pretty good. That was in October.
So now its summer and its not very well at all.
I couldn't figure out what the problem was so I took it to a local guy. He is hesitant to recommend anything for his lack of knowledge on retro systems. He evacuated the system re-filled it to spec -10% but the temp will only cool to 55 degrees with the low pressure cutout bypassed. Then if he adds an ounce more the high pressure side cuts out. He thinks there could be a blockage somewhere.
I am trying to get her fixed up for a trip on Friday to the Biltmore but cant get it into a different shop ( AC specialty )till Maybe next week.
I am leaning toward a compressor problem but am seeking advice from the knowledgable gurus that frequent this forum.

Thanks!!

 

[boomdriver]

well, the blockage can be confirmed by the gauge readings. Low pressure while running should be a stable number and the high side has its number as well. When the low side is higher than normal and the high side is where it should be, that can indicate a block. The system has very specific low pressure areas and the same for the hi-side.
Look in the orifice tube. Thats usually where the junk collects. next would be the condensor up front. Might have a pinched tube or some trash caught in a bend.
There is almost no way around it, you;re going to have to open it up and blow SECTIONS out one at a time and use solvent and LOTS of air. Blow from both directions. Use a paint strainer or a white sock over the exit to catch any evidence. If you see metal slivers toward the orifice or the evaporator, its compressor time...again. Its unlikely that there will be anything in the accumulator passing into the compressor because everthing has to pass thru a screen/bag in the dryer and the oil sump tends to collect the loose stuff.Trash has to get past the orifice to get anywhere else. Blow sections clean mostly to start clean with no dirty oil in the system.

Break the system at the orifice, and at the condensor, dryer(dont blow dryer or comp out) and blow thru and re-assemble one piece at a time. New O-rings on anything that comes apart.

Now, if the hi-press cut out engages, does it come back after a couple seconds? If so, thats just normal cycling. Is the main fan kicking on as the a/c is on? If the system builds too much pressure or heat, the switch kicks it off till pressure drops. Cooling fan behind radiator should come on almost with the compressor, otherwise it will cut the syst off.

Another thought.....the clutch MAY have burned up if the compressor seized while driving. Changing the clutch may have free'd the compressor and allowed it to spin again with poor performance.

 

[gmjunkie]

Have you checked for road deb're restricting air flow through condenser??Also check to see if a homeless critter found a new home in your Evaporator housing last winter!!:W:W:W
I've had 3 customer vehicles this year that had unwanted guests build a home in the Evap Housing!!
2 vehicles didn't have any evidence of any kind inside the vehicle!!

 

[CROOZ1N]

The original compressor locked up solid. the reman'd replacement clutch went out on the road in the middle of a trip and we couldnet find a replacement along the route. By the time we got to where we were going and did get a clutch the shaft was fubar so thats why I put the used unit on. At first it was simply to get me back home . The fact that it worked was simply a bonus at the time. Thanks for the response.

Junk I had in mind to get up under the front and vacuum out the leaves and stuff last night but got sidtracked. I'll do that and post some pressure readings as well.

On another forum Its being said that the GM condensor is not capable of cooling at max possible with R134a and that the best bet is to replace with different design condensor. Are they tying to sell me a condensor or was the condensor redesigned in 94 for R134a.

Any thoughts?

 

[gmjunkie]

On another forum Its being said that the GM condensor is not capable of cooling at max possible with R134a and that the best bet is to replace with different design condensor. Are they tying to sell me a condensor or was the condensor redesigned in 94 for R134a.

Any thoughts?

Thats BS!! A properly retro fitted system,You can Hang Meat in!

PS.Don't ride around your Brass Monkey though,You'll have to retrieve his "Nads" from under the passenger seat!!:L:L:L

 

[88C4]

My 88 a/c system was converted last year and it gets nice and cold. The temp only goes down to 60 but that is plenty.

 

[boomdriver]

My 88 a/c system was converted last year and it gets nice and cold. The temp only goes down to 60 but that is plenty.

mine is a retrofit 134-a that brings cabin temps down to 58-60 at best, but thats friggin wonderful when its 98 w/90% humidity outside.

Use a little less 134a in a r-12 system. How much depends on how efficient YOUR condensors heat exchange rate is. If its beat up and cannot pass air, then replace it. Otherwise adjust the amount of gas by the gauges. 45lbs low side is a good place. Its approx 2 lbs gas.

 

[CROOZ1N]

Ok I did some more testing today. Ambient Temp 78
Static pressure 110 lo side 125 Hi side.
At Idle the lo side cycles between 20-33 and the Hi side 170-250
At Hi Idle the low side cycles 18-32 and hi 225-320

I took the small access panel off the top of Evap housing and nothing is in there . Blend door is shifting fully.
I sprayed water on the condensor while running and the hi side dropped to about 200 but it didnt get any cooler inside.

I took some videos of the guages so you can see how the cycle went.

YouTube - MVI_0003.AVI

YouTube - AC Hi IDLE.wmv

 

[CROOZ1N]

Many Thanks to GMJunkie for taking time out of his day to help me try and get this thing cooling better.

 

[gmjunkie]

Many Thanks to GMJunkie for taking time out of his day to help me try and get this thing cooling better.

I think you need a little more refrigerant!
Put the the controls Max Cool,High fan and add a little at a time till it just quits cycling at 1000 RPM and then just a Little more!!



PS. If it won't quit cycling and the high side gos much past 350,you probly have a restriction in the Low side!
Probly Orifice tube or VOM! (VOM= Variable Orifice Module or Smart Tube)

 

[Curious George]

Thats BS!! A properly retro fitted system,You can Hang Meat in!

PS.Don't ride around your Brass Monkey though,You'll have to retrieve his "Nads" from under the passenger seat!!:L:L:L

I have a '92 that I retro-fitted with R-134 and my vent temps are 44* ~ 46* with blower on high while driving. The OE condenser is fine, however a parallel flow one would be nice, it is not necessary.

CG

 

[CROOZ1N]

Many thanks to all who helped with this.
The root cause was that there was what looked like lint on the orifice tube. I replaced the orifice tube recharged and it kept us pretty cool all weekend. Temps about 48~50 or so. I may be able to better that but was satisfied for the trip. I'll give her a little nudge more coolant and see how she does.
The biggest thing that I saw and what I didn't realize was that both the Hi and Low side readings stay fairly steady all the time.

 

[Curious George]

Many thanks to all who helped with this.
The root cause was that there was what looked like lint on the orifice tube. I replaced the orifice tube recharged and it kept us pretty cool all weekend. Temps about 48~50 or so. I may be able to better that but was satisfied for the trip. I'll give her a little nudge more coolant and see how she does.
The biggest thing that I saw and what I didn't realize was that both the Hi and Low side readings stay fairly steady all the time.

One item I forgot to mention, and it makes a difference when retro-fitting your system to R-134 from R-12, is the orifice tube size. Typical GM orifice tube (at least for the Corvette) is .072". When using R-134, in an R-12 designed system, use a Ford "light blue" orifice tube (.068").

The slightly smaller diameter orifice will cause a greater pressure differential, across the orifice tube, into the evaporator, and allow you to get your vent temps a few degrees cooler.

CG

 

[raidoman]

AC Problem

did they replace the dryer wiht the new style?

 

[MBDiagMan]

CROOZIN,

I would recommend that you go buy a lottery ticket. You are VERY lucky.

In the event of an internally failed compressor, which is how yours failed, in ANY refrigeration system, it is IMPERATIVE that you flush all components thoroughly to remove debris before installation of the new compressor. In almost all cases where this is not done, the debris circulates through the new compressor and wrecks it. Sometimes compressors fail or lock up in a way that produces minimal debris, but that is an unsafe assumption.

The reason you had replace the orifice later on is because it got plugged up with this debris. In the system flow, the orifice tube is AFTER the compressor so it can't act as a filter to keep out this damaging debris.

You dodged the bullet my man, go buy that ticket. Beginners luck probably prevailed.

By the way, I began converting various systems from R12 to R134a way back in the mid nineties. My 88 Vette was the first that I converted and I had beginners luck. That system is still working great although I have made a few repairs to it along the way. Performance wise the a/c in this car has the ability to make a Polar Bear SCREAM for mercy. In most cars originally equipped with R12 this is not possible. Typically a 15% performance efficiency loss comes along with the conversion. Some cars, our Vettes included, have adequate condensor capacity to offset this loss.