82 240D AC No High Side Pressure - Page 2 - PeachParts Mercedes-Benz Forum

nelbur · #16 07-18-2016, 10:00 PM

There is almost zero chance that your high side pressure could be zero. Even if you have the 134a adapters on the schrader valve, you should be able to see the center stem of the core that must be depressed by your connector for your gauge. I suspect you are not depressing the stem and therefore see zero pressure.

Demothen · #17 07-18-2016, 10:18 PM

Ultimately you are going to need to open up the system no matter what, so there is no point in theorising here. You need to have the system evacuated, then start opening it up and flushing it. You might as well start by pulling the high side fill port if possible and seeing if there is anything clogging it. Honestly it's probably best to just do a complete service with a flush, new compressor, etc.

ROLLGUY · #18 07-21-2016, 10:41 AM

Quote:

Originally Posted by Demothen

Ultimately you are going to need to open up the system no matter what, so there is no point in theorising here. You need to have the system evacuated, then start opening it up and flushing it. You might as well start by pulling the high side fill port if possible and seeing if there is anything clogging it. Honestly it's probably best to just do a complete service with a flush, new compressor, etc.

Agreed. However, I would not waste your time and $ on the R4 if I were you. You too could spend thousands on the A/C, and maybe get it working for a season, but probably not much longer.

leathermang · #19 07-21-2016, 11:50 AM

Quote:

Originally Posted by ROLLGUY

Agreed. However, I would not waste your time and $ on the R4 if I were you. You too could spend thousands on the A/C, and maybe get it working for a season, but probably not much longer.

Rollguy, I have always hoped that your R4 to Sanden ( or whatever newer design ) was effective. You have been open about problems ..... and your efforts to correct them... that is great..

BUT... the latest reports STILL involve belt tension problems as far as I can determine... AND you have now added a support which requires a hole in the pan (?)....

I wish you could get everything worked out so it would be a slam dunk to recommend your kit as long as the people could afford it.

A properly rebuilt R4 of the LATER serial numbers....( as recommended by Trey of Carlisle Auto Air in San Antonio )
has millions of units operating just fine out in the real world using R134a.

300d 4 ME · #20 07-21-2016, 12:34 PM

I'm not quite sure whats going to happen with the AC for right now. I do know one thing though, " I'm not spending thousands like the last guy!".

It will have to be a later R4 compressor though. I know of many that still work just fine.

We don't drive the car that often. Even when it's 90 outside, with the windows down, and the car moving. It is not that bad at all. Plenty of air moving about.

Thanks for all the tips!

leathermang · #21 07-21-2016, 12:53 PM

Quote:

Originally Posted by 300d 4 ME

I'm not quite sure whats going to happen with the AC for right now. I do know one thing though, " I'm not spending thousands like the last guy!".

It will have to be a later R4 compressor though. I know of many that still work just fine.

We don't drive the car that often. Even when it's 90 outside, with the windows down, and the car moving. It is not that bad at all. Plenty of air moving about.

Thanks for all the tips!

Many Millions... working just fine...
most of the time when you get reports of them not working has to do with less than total cleanliness at some point in dealing with the AC system... or switching to an oil /refrigerant combo which does not mix as well as it needs to for the ( non sump ) R4, which relies entirely on the oil carried around the system by the refrigerant.

ROLLGUY · #22 07-21-2016, 01:32 PM

Quote:

Originally Posted by leathermang

Rollguy, I have always hoped that your R4 to Sanden ( or whatever newer design ) was effective. You have been open about problems ..... and your efforts to correct them... that is great..

BUT... the latest reports STILL involve belt tension problems as far as I can determine... AND you have now added a support which requires a hole in the pan (?)....

I wish you could get everything worked out so it would be a slam dunk to recommend your kit as long as the people could afford it.

A properly rebuilt R4 of the LATER serial numbers....( as recommended by Trey of Carlisle Auto Air in San Antonio )
has millions of units operating just fine out in the real world using R134a.

No holes need to be drilled, and all the parts are bolt-in. The belt problem is just cheap belts. Only adjusting a couple times is all that is needed, and that may even be the case for a more expensive belt. When I run out of the batch of belts I have, I will provide a better belt. However, the customer is always welcome to supply their own better quality belt.

As far as the later serial numbered R4's, yes I agree that they are still out there and working. However, I still would not recommend a rebuilt or "NEW" unit, as they probably use Chinese parts in them. I work closely with my local A/C shop, (sometimes even help on busy days during the summer), and I quite often hear about bad rebuilt R4's. I replaced one in a Chevy van the other day that leaked. It was a NAPA re-manufactured unit put on recently by the customer. Suffice it to say, I don't have a good opinion of ANY R4, new, used, re-manufactured, or otherwise.

BillGrissom · #23 07-21-2016, 03:26 PM

Re R4 vs Sanden, I have both on my 300D's and both work fine and about the same cooling as best I can tell. GM owners have had many problems w/ R4's. But, those are typically mounted up high where the oil doesn't want to stay, unlike in our cars, and an R4 doesn't have an oil sump. If flushing your system, lookup PAO 68 oil. It doesn't absorb moisture like PAG, stays put better in the compressor, and thus is more efficient (less oil coating condenser and evaporator tubes).

Only minor issues w/ Rollguy's brackets, and he has been great at supporting the early customers w/ upgrades. The extra brace added to the upper oil pan worries me a little since that pan is aluminum and would be a big job to replace if the brace made it crack, but the factory bolted other parts to it. The pan bolt supplied with it was too long and broke my damper indicator pin off, but I don't need that in my 1985 anyway. I did have trouble keeping the brace bolted to the main plate since it didn't quite reach and the gap wasn't parallel, but my latest bolt w/ jam nut seems to be staying on. The belt has stretched until I reached the limit of adjustment. I can't rotate the compressor in enough to fit a shorter belt (come in 2" increments of circumference), so would have to remove it, and accessing those pivots bolts is tough. I will probably retrofit with allen bolts and such to make easier.

funola · #24 07-21-2016, 04:21 PM

300d 4 ME, could you try measuring the hi side static pressures again with your HF manifold gauges? I have the same set and those quick couplers are real funky/ fuzzy. I have seen mine read zero when it should read 70 psi after turning the valve on the quick coupler c.w. to depress the Schrader. I had to turn the valve ccw then cw to get a reading. It may also have something to do with how far it you pushed the quick coupler. Try to push it as far as it will go and make sure the locking collar is fully engaged before turning the valve cw.

funola · #25 07-21-2016, 04:29 PM

Quote:

Originally Posted by BillGrissom

............If flushing your system, lookup PAO 68 oil. It doesn't absorb moisture like PAG, stays put better in the compressor, and thus is more efficient (less oil coating condenser and evaporator tubes).
..............

Here's an interesting article on PAO 68 oil PAOIL - The Refrigerant Oil Company .

This is copied from the article:

"Low miscibility with refrigerant – high miscibility leads to lubrication loss, heat transfer impedance, lower viscosity, foaming in low pressure areas, low temperature in the crankcase (refrigerant boil off) giving low lubricity, carry over of lubricant throughout the system and oil films on condenser and heat exchanger walls."

It says high oil miscibility in not desirable. Low miscibility is better. I thought high miscibility is better but apparently not true? As long as the miscibility is enough to move the oil around the circuit to the compressor, that is all that's needed. Too high miscibility creates problems as cited.

leathermang · #26 07-21-2016, 09:04 PM

Quote:

Originally Posted by funola

Here's an interesting article on PAO 68 oil PAOIL - The Refrigerant Oil Company .

This is copied from the article:

"Low miscibility with refrigerant – high miscibility leads to lubrication loss, heat transfer impedance, lower viscosity, foaming in low pressure areas, low temperature in the crankcase (refrigerant boil off) giving low lubricity, carry over of lubricant throughout the system and oil films on condenser and heat exchanger walls."

It says high oil miscibility in not desirable. Low miscibility is better. I thought high miscibility is better but apparently not true? As long as the miscibility is enough to move the oil around the circuit to the compressor, that is all that's needed. Too high miscibility creates problems as cited.

No one is talking absolute values.... you need a certain amount.. which you can count on with the recommended oil / refrigerant combination.... if you start mixing and matching you risk not having enough oil per unit of refrigerant moving around the system. The R4 is more prone to problems than others due to not having an oil sump.