Scott Simoncic

Hey Guys... Getting hot here and my A/C is on the Fritz... Here's the story, when I bought it in October of last year, it was ICE cold... I've done nothing to it. A month and a half ago we had a warm spell, and it was not blowing cold... Read the REST data and it was low on refrigerant.... Added a small amount, got cool but not cold... Still technically was low on 134. Got hotter, and the A/C didn't really work at all, compressor kicked on, but sensor #7 in the REST was at 4, the bare minimum for the compressor to kick on. So now, I decided enough was enough, my CLK 430 ran with the pressure around 13-15 and was cold. So I bought a couple cans of 134a refrigerant only (No dyes, no sealants, no "boosters" or anything else). Proceeded to put the fill hose and gauge on, gauge was off the chart high, but we have variable systems so I disregarded. Started the car and put the AC on and in REST mode. Filled the car until about 12 on sensor #7 was reached.. About 18oz's of 134. A/C still hot. I pressed the EC button to turn the compressor off... Then pressed it again to turn it back on, the pressure shot up to 30, then the compressor kicked itself off, this happened a few times, then went back down to 10. I recovered some of the refrigerant thinking it was too high, but this problem happens intermittently. Here is the Data:

10 Minute drive in the morning about 68 degrees outside.
1.)74
2.)84
3.)79
4.)78
5.)78
6.)192
7.)10
8.)85

15 Minute Drive 82 Degrees Outside

1.)85
2.)107
3.)92
4.)91
5.)91
6.)195
7.)15
8.)10

GatorMB

I am going to take a stab at this from the chart:

Low pressure readings on a 80^ day in the sun should be around 60
High pressure readings around 275 - 325 with the condenser fans on.

The low pressure switch usually kicks the compressor off around 20.

If you are reading 30 which is low the pressure will drop low enough kick the compressor off under mild acceleration.
Really need to see the high pressure reading from a refrigerant gauge set. If we observe the high pressure is too high and the low is too low then the system is plugged.

Gator

Code 1 = Inside Temp
Code 2 = Outside Temp
Code 3 = Left Core Temp
Code 4 = Right Core Temp
Code 6 = Coolant Temp
Code 7 = Refrigerant Pressure (This is the important one)
Code 8 = Refrigerant Temp

Scott Simoncic

Ok, I'll get ahold of a set of gauges this weekend... What would plug the system? Expansion Valve?

GatorMB

The receiver Drier has desiccant beads that absorb moisture, when the drier has absorbed all that it can the beads expand and the bag breaks. This sends them right to the expansion valve.

Debris from the compressor collects in the condenser creating extra high pressure. Heat saturated freon never gets to liquid form which is required for the expansion valve to atomize the freon. Flushing is required

Other forms of blockage in the expansion valve include moisture on the needle valve assembly that corrodes the needle action, the valve never opens and has limited flow.

I bet it is low on freon, to check the drier on a charged system just feel it by hand, it should be hot on a healthy system.

Cheers

Scott Simoncic

Should I just vacuum down the system and do a full charge?

Oh, and does anyone know the correct Low-Side recharge Pressure for a CLK 55 in about 80 degrees ambient weather?

Chadzu

These systems need to be charged by weight. Pressure is unreliable due to the variable displacement pump.

GatorMB

The Variable displacement pump operates off a pilot valve that regulates the volume of freon by means of a swash plate on reciprocating piston assembly.

If the pilot valve acts up it can cause a lot of different symptoms. Most from the past stop pumping period and adding freon never recovers the system.

Sensor readings are for general use by us and required by the control system to moderate air flow and temperature, cooling and heating. Nothing replaces hanging some gauges on the AC system to determine health.

An empty system should be evacuated at least 30 minutes prior to charging. The vacuum pump removes moisture from the system and keeps it healthy in many ways.

All the Best

Scott Simoncic

Thanks for the info guys.... I had some interesting time trying to figure this out.. The other night it was still warmish, and It would cool more with the compressor on, by about 10 degrees... I've only had this happen that one night... I attempted to add more refrigerant to get it up to the 12 level, got it there, still warm air... After that, it would drop down to about 9 with the compressor off, then when the compressor would kick on, it would jump up to 30, I had some evac'd and I'm still getting readings all over the board with pressure on #7 and at no time any cold air.

Chadzu

Keep us posted, I'm having issues with mine as well. In my case I'm not getting differential between high and low. I have pretty much decided the compressor is going to need to be changed.

Scott Simoncic

Chadzu, I've pretty much come to the conclusion that my compressor is out too.... It's either that or the expansion valve... Neither of which I want to tackle... But I will, because I can't do the no ac thing here in the Central Valley of CA... I'll have to drive around my '83 RX-7.... A/C works in that beast... Original NipponDenso Compressor in that car... Actually, original everything... Small leak somwhere, but honestly its such a small system, I could care less. I'd rather not drive the project car with 355K miles and a rotary that puts out smoke like mad, has basically no window seals, no power steering, no anything really.

GatorMB

83 Rx7 wankel makes a great rally and Autocrosser. All fun

Scott Simoncic

Ok.... It's fixed... Took it to my buddy who's a Senior Master Tech... System had air in it.... Vacuumed it down to 30 psi for about 20 minutes, held pressure, then filled it with new 134 and PAG 46... Runs quiet and cold now.

Yes, the Wankel is fun but it needs apex seals badly, I can smoke the block out with just oil burn if I want to.. It's a project car, I'm actually restoring it back to original, plus some extras. I want to do an FC injected 13b since 12a's are becoming rare to get parts for, blocks are impossible to find, plus the fuel injection will be NICE, with the extra power especially. I also need to find a gsl rear end with Disc brakes. I'm adding all of the electronic extras it didn't come with, I have the equalizer and fader / balance joystick... Trying to pinout them correctly to work with my aftermarket eclipse deck. Been some work.