Automotive Air Conditioning Information Forum

Kind of a big difference from an SBC / R4 to an LS.

So what sort of fan arrangement do you have?

Which Sanden?

Missing a lot of info.

rosco11 wrote: ↑Mon Jun 27, 2022 2:55 pm Ok, at 2k rpm outside temp 93 degrees.
high side - just under 300
low side - just under 40

With the engine at 2,000 RPM and the high-side pressure at just under 300 PSI, it seems as though the condenser isn't condensing sufficiently for whatever reason. At that ambient, the high side should be in the neighborhood of 220-240 PSI if everything is working as it should.

Additionally, a low-side pressure of just under 40 PSI means that the evaporator temperature is about 45°F—not nearly cold enough to cool the air flowing through the evaporator sufficiently, especially on a 90-degree-plus day.

rosco11 wrote: ↑Mon Jun 27, 2022 2:55 pm evaporator temp taken at the tubes going into and out of evaporator.
inlet temp - 75
outlet temp - 64

Usually, the inlet tube temperature should be about the same as the outlet tube. The temperatures you posted seem "off" compared with a low-side pressure of just under 40 PSI (evaporator at +/-45°F). Are you sure your measurements are accurate and that you took the temperature of the liquid line after the OT?

John:

I looked at those evap line temps and thought the same thing, but figured it was undercharged with poor liquid delivery... based on an R4 compressor.

Eventually we will find out there are aftermarket brackets and a tiny sanden compressor. An electric fan of some sort.

and a large gap between the cond and the rad

numbers with a full 48oz

evaporator inlet outlet temps
inlet 73
outlet 76

pressure readings at idle
high 275
low 52
pressure readings at 2000 rpms
high 325 with needle bouncing wildly
low 45 to 48

When the engine is cold, car side evaporator air temps about 61 degrees and high side compressor readings at 250. When it is hot temp is 76 degrees and high side compressor at 325 and bouncing.

the gap between the radiator and condenser is filled with foam. Sanden 508 compressor.

The ac lines were shortened significantly because of the change of location. There was also a canister if some sort on the low pressure line right before it entered into the original compressor that was cut off. Not sure what it did.

To the above poster that feels there is a big difference between factory r4 and sanden compressor. Only difference is the amount of oil recommended. Pressures are he same. Sanden compressors came factory on a lot of rvs and 18 wheelers. They are not something new, just different. Only reason i have one on this project is because it was free and mounting hardware is easy to find.

I appreciate the help. i am at a loss as to what is going on and am giving it the old college try before throwing in the towel and dumping 1700 bucks on a vintage air system which, IMO after installing a couple, does work well, but it is very fragile. No where near as tough as a factory system and components. It was probably designed for hobbiest whose cars sit in a garage, not a K5 with a suspension like a rock that gets driven every day.

Your pressures are high. You previously stated your pressures dropped when the condenser was hosed down. A response was given such that the water test you did demonstrated inadequate condenser performance. As far as I am concerned that is still the case. Surely there are more issues than that.
These swaps are never easy.

Does the larger diameter hose enter the cond at the top and the smaller diam hose exit at the bottom?

Suggest before you grab a VA off the shelf to stay with the consultants here, most posters have no idea just how good they are.
Wait for them to get back on.

Yes, and i am sure the same would happen now. It is friggin HOT in texas. Getting air does not mean much if it is getting HOT air. Cold water will do it every time.

There is a problem with this system. I do not think it is the compressor. And everything else is new but that does not mean it is working like it should. I went through 5- o2 sensors before i finally broke down and bought factory GM sensors at 4 times the cost before i found two that worked. The same might be going on here. Maybe the condenser is bad. Maybe the compressor really is bad.

The bouncing needle on the high side should not be happening. And the temp going into the evaporator after the orfice tube should be a lot colder. The refrigerant is not cooling like it should. This is the second orfice tube with the same results, one white, one red. So i think the problem is happening before the orfice tube. Compressor, another condenser or maybe the shorter lines and lack of canister have something to do with it.

Currently, because of the low pressure side at 51, i think it is a little over charged. But not enough to make that big of a difference.

I do not want to blindly throw money at it. But 73 degrees going into the evaporator is not going to get me where i need to be.

Even though you bumped-up the charge, it appears that insufficient liquid refrigerant is making it to and through the evaporator based on your latest evap line temperatures. That might be caused by the condenser (not enough airflow, inadequate fan, defective component, etc.), or by a compressor that lacks enough displacement. I believe the R4 had a couple more cubic inches compared to the largest Sanden 508, but bohica2xo would know for sure. It's also possible that there are two OT's in the liquid line restricting the flow. I've seen that a time or two.

Thanks for the reply.

Pretty sure i can rule out 2 orffice tubes. The only other place one could have been would be in the condensor, but i would have seen it when i flushed the system. But, i did move from a white orffice tube to a red orfice tube which does shrink the orffice down to .062 from .075 in the white. But being i have the same temperature range with both, not likely.

I can not rule out the condenser.

I can rule out the Sanden 508 capacity though, have used it in two other systems, both vintage air, in a 70 c-10 and a 69 GTO. No problems with either.

I can not rule out the compressor itself as being defective. It will easily go past 350 and climbing on the high side if i block the air flow. But that only means it is compressing. It does not mean refrigerant is not leaking past the pistons. I also can not rule out that maybe the 508 is designed for a smaller condenser and evaporator.

Air flow i can rule out also. I have used this two speed T-bird fan on all of my projects. On high, it flows a lot of air and i set it up to turn on the high fan whenever the compressor is switched on. As well, i have used foam around the edges of the condenser to seal it against the radiator which is also sealed against the fan with no gap.

So is it worth swapping the Sanden with a R4 and replacing the condenser again? Is either of those likely to get me another 10 degrees? After new mounting brackets, compressor, condenser and Freon it is a good 500 bucks. I would need to be confident this will get me there over going the vintage air route.

There is a lot going on here, I haven't read it all but here's what I see.

Sanden 508 is a small compressor, 138cc which is tiny compared to say current production Tahoe 200cc.

Depending on which LS you've swapped in there are some really great compressors that will bolt right on. If it's an iron block truck LS, I'd choose a Denso 10S20 or something like that. LS1 came with Delphi v7, also great for a swapped setup.

How's your drive ratio to the Sanden? Measure the ratio of engine crank pulley diameter to compressor pulley diameter.

YOU HAVE NO IDEA HOW MUCH CHARGE THIS BLAZER NEEDS. You replaced almost everything, most of the charge when operating is in the condenser which you changed and the liquid line.

My feeling is that you have it overcharged. You have very little cooling going on, but high condenser pressures.

Determining charge on a CCOT system takes some patience. White OT is one of the biggest and you have a tiny capacity system at the moment. Start on the low end of sizes, maybe orange or blue. You operate at high blower, engine 1500 to 2000 hold it there, start undercharged but a reasonable amount. Add charge 1oz at a time, add more each time if you are way off. Evap out pipe will be warm and inlet cold when you are undercharged. When the evap out pipe is same temp as inlet, add about 4 to 8 Oz more. Record low side pressure, high side, ambient, vent temp.

I wouldn't waste time with that Sanden. Yes it was made in Texas, but I'd go for 200cc Denso