I've owned diesels with both the R-4 and Nippondenso compressors. The cars with Nippondenso compressors don't seem to be as affected by compressor drag, but it's an apples & oranges comparison. We're talking about different chassis with different engines. It probably has more to do with the engine - OM603 vs OM617.

BTW, the Nippondenso isn't really a rotary compressor. There are five little cylinders in there with pistons boinging back and forth. The cylinders run parallel to the length of the compressor case, and are arranged around the circumference. Likewise it's my understanding the R-4 is a four cylinder compressor, with the cylinders arranged in a radial pattern, like a radial aircraft engine.

Isn't a true rotary compressor more along the lines of a turbine?

- JimY

That's correct, few compressors are vane type. Most have pistons and cylinders in either a radial arrangement or in line with the length of the compressor actuated by a swash plate.

Have a great day,

Yes, true in all aspects... but most of the time people are talking difference between the rocking and rolling of the York type compared to the swashplate type....smaller bites spread around a rotary configuration... as compared to the two pistons , which may even go up and down together, on the York... which you can imagine is a nightmare to get balanced by adding something to the crankshaft throws....

Anybody have any knowledge/experience/opinions about them?

Both my Euro 123's have Sanden compressors as part of their aftermarket a/c's. From what I can tell they are quite good.

To illustrate leathermangs point, compare the vibration of a two cylinder Harley Davidson to a V12 or even a six cylinder. More cylinders provide smoother operation.

Have a great day,

So a rotary AC compressor works somewhat like - I’m thinking of a hydraulic steering pump?

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89 300E
79 240D
72 Westy
63 Bug sunroof
85 Jeep CJ7
86 Chevy 6.2l diesel PU

"The object of life is not to be on the side of the majority, but to escape finding oneself in the ranks of the insane."
Marcus Aurelius

Yes, it has little pistons in it... the ' rotaries' and the radial Delco.... and the big pistons in the york.....
but remember , it never has liquid refrigerant in it....
low pressure gas in.... high pressure gas out....

Ok, my AC blows good and cold, and feels good after a few minutes with windows down and moving. Sunroof open adds more breeze but the sun cooks my head.

1. The controls work fine as long as I never touch the off button. Once I hit the off button and then on again, fan will sometimes respond and sometimes not. Finally after jamming buttons again and again it will start up. Best bet--CCU or vacuum lines to fan?

2. I am starting to experience overheating in stop-n-crawl traffic. I am thinking that the larger aux. fan is step 2 after a good flush.

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1984 300SD 326,997 miles and counting . . . No wait, my odometer is still dead

It sounds as if the fan motor is worn out. Probably brushes, but possibly bushings as well.

Yes, that aux fan, if not operating will bring up your slow traffic temp. Even worse, it will allow your high side pressure to get dangerously high. It is actually there to bring down high side pressure when necessary.

Good luck,

Hello,
I can comment on A/C performance in the tropics(Kuala Lumpur, Malaysia, ambient around 90-110F,100% humidity)!!!!Car is W115 200 gasoline with Sanden 507, R-12 fill with 11 blade Bosch fan ahead of condensor and 6 blade viscofan on w/p hub.
Car starts at 130F interior air temp, but 5-8 minutes of slow driving drives air temp down to 70F(vent temps at 45F) and any further driving, up to approx. 40mph, and I have interior at 58-65F with vent temps at 35-38F.
In North Carolina, W124 260E struggles in summer to get vent temps down to 45F, interior air around 65-70F. The vacuum element for the recirculate door is shot and I never did get around to replacing it.
I have found that the *modern* aerodynamic cars with heavily sloped front and rear screens let too much heat into the interior, for many years I drove an Opel Manta A with a gigantic shallow rear screen and that car was like an oven, interior air never getting below 70F even with vent temps around 34-36F. I hate the sharply sloped front screens on the cars from the late 1980s to date as the heat soaking is helped along by front and rear screens.
You guys are fortunate in the US that you can have almost *black*(privacy) glass behind the driver, not so here. So I have an black nylon cloth sunscreen permanently fixed to the rear window and I fix a silvered sunscreen to the the front screen when I park.
The R134 systems do not do well here for some reason, taking much longer to pull down interior temps from a heat soak condition, a W210 that I frequently ride in always *roasts* passengers for the first 15 minutes or so.
Just my 0.2 cents, have a good weekend

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Nachi11744

Fan Moter, eh. Did not expect that. Assumed it was elec. problem with control buttons. Fan Motor blows out air strongly when running.

Aux. Fan is working, just experienced near over-heating on a long slow-crawl up FM 2499, earlier this week.

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1984 300SD 326,997 miles and counting . . . No wait, my odometer is still dead

The buttons on my wagon were that way.... I never knew when they were going to follow my " suggestions"......sometimes later, for no known reason they would do what I asked... other times they completely ignored me....