KLIMA Basics missing from this forum - PeachParts Mercedes-Benz Forum

Jeremy5848 · #1 11-30-2006, 09:41 PM

When I bought my '85 300D Turbo, I found a suspicious relay in the box just forward of the KLIMA relay. Eventually, I learned about KLIMA failures and the use of an ice cube relay to bypass the problem and restore a/c operation. I have a replacement KLIMA but would like to know a little more before I plug it in. Although this forum (especially the FYIs) and various books mention KLIMA from time to time, none give a basic explanation of what KLIMA is and what KLIMA does. It reminds me of the FSM -- it assumes you already know.

Therefore, I have assembled what I have been able to glean from the various threads (the books are useless) and present it here for the benefit of other newbies like myself. Perhaps others will chip in with things I have missed.

Anyone have a schematic showing all of the wires to and from KLIMA? I have the FSM on CD-ROM and several other manuals but can't find KLIMA. Perhaps a W124 manual might have it.

What is KLIMA?
KLIMA is an electronic relay system that controls the air conditioning compressor's electric clutch. It allows the compressor to run (engages the clutch). KLIMA looks at many things.
1. It looks at the ACC to see if you want cooled air.
2. It looks to make sure the compressor is not frozen. If the compressor is frozen, the pulley won't turn. The engine would then eat the drive belt and perhaps do other damage.
3. It looks at engine temperature, or maybe coolant temperature, or maybe both. I don't know why. Inputs, anyone?
4. More?

In my '85, KLIMA lives on the driver's side of the engine compartment, just ahead of the fuse box. Earlier 300Ds don't have KLIMA, I'm told. W124 and W126 cars also use KLIMA.

If KLIMA fails, the compressor won't run. Because KLIMA is expensive, people years ago developed a work-around using a small "ice-cube" relay. My car has this work-around. It is recommended on this forum that this not be used as a permanent replacement but no one bothers to say WHY. I assume that it is because all of the safety features are eliminated -- all the relay does is turn on the a/c clutch when the ACC calls for cold air. Right?

Anyone have anything to add?

Brian Carlton · #2 11-30-2006, 10:07 PM

The "Klima" on the '85 is a solid state relay that controls the compressor clutch.

It takes signals from the following:

1) Signal from the CCU going through the Evap. temp switch and the low pressure cutout switch. This signal tells the Klima to close.

2) Signal from the kickdown switch. This signal tells the Klima to open.

3) Signal from a temperature switch. This signal tells the Klima to open if the temperature it above the setpoint.

4) Signal from the tach. I can't figure what the Klima does with this on the '85.

So, if the signal is present from the CCU and there is no kickdown signal and no overtemp signal, the Klima should close the relay and the clutch should engage.

On the '85, you have very little risk of using the ice cube relay as a permanent replacement. You only lose the capability of more power when the kickdown switch closes (pedal on the floor). You also lose the capability of the relay to shut the a/c compressor down if the engine gets too hot. But, you would do this yourself.........right?

On the '86 and later vehicles with the 603 engine, the Klima is more sophisticated and is also present to prevent shredding the serpentine belt if the compressor locks up. Using the ice cube as a workaround is more risky with these engines.

JimmyL · #3 11-30-2006, 10:16 PM

I don't know too much about the Klima, but I do know that if the tach isn't working, the compressor will not be switched on through the Klima.
Somebody bypassed my Klima using a wire on the pins. Pic to follow.......

**I'm assuming you saw this thread in your search**

Klima Relay issue

Jeremy5848 · #4 11-30-2006, 10:30 PM

Quote:

Originally Posted by JimmyL

**I'm assuming you saw this thread in your search**

Klima Relay issue

Yes, I did. A most interesting "fix." What did you end up doing about it? Did you replace it or put in an ice-cube replacement?

Jeremy5848 · #5 11-30-2006, 10:38 PM

Quote:

Originally Posted by Brian Carlton

The "Klima" on the '85 is a solid state relay that controls the compressor clutch.

On the '86 and later vehicles with the 603 engine, the Klima is more sophisticated and is also present to prevent shredding the serpentine belt if the compressor locks up. Using the ice cube as a workaround is more risky with these engines.

Thanks, Brian. That is exactly what I was looking for. I especially appreciate your making the point about the difference between cars with multiple belts (like my '85) and the later 603 engines that use a single serpentine belt.

I shall experiment with the KLIMA that I got from whunter. Perhaps I will be able to get rid of the workaround.

Others have mentioned opening up KLIMA and fixing it. If the CC and ACC pc boards can be fixed by resoldering, maybe KLIMA can be fixed too. If I figure anything out, I'll post results and pictures.

JimmyL · #6 11-30-2006, 11:06 PM

Quote:

Originally Posted by Jeremy5848

Yes, I did. A most interesting "fix." What did you end up doing about it? Did you replace it or put in an ice-cube replacement?

Didn't do anything about it, as I consider it "fixed" the way it is. Since our '85 W123's don't use a serpentine belt, I really can't see much need for it to be working.
The pressure switch must be on down the circuit from the relay, as the compressor won't activate if the switch is unplugged.

Carrameow · #7 12-01-2006, 04:35 AM

I sure will be watching your posts in the future. Can't wait until you have transmission trouble...

Jeremy5848 · #8 12-01-2006, 04:19 PM

Quote:

Originally Posted by Carrameow

I sure will be watching your posts in the future. Can't wait until you have transmission trouble...

Thanks a lot!

Transmissions are easy. Lots of information, manuals, and special tools available (the most important one being the "credit card" tool). It's the little stuff that bugs me. Everyone assumes you already know what all of the little bits and pieces do but I don't even know what half of them are, much less what they do.

riethoven · #9 12-01-2006, 04:24 PM

Quote:

Originally Posted by Brian Carlton

The "Klima" on the '85 is a solid state relay that controls the compressor clutch.

It takes signals from the following:

1) Signal from the CCU going through the Evap. temp switch and the low pressure cutout switch. This signal tells the Klima to close.

2) Signal from the kickdown switch. This signal tells the Klima to open.

3) Signal from a temperature switch. This signal tells the Klima to open if the temperature it above the setpoint.

4) Signal from the tach. I can't figure what the Klima does with this on the '85.

So, if the signal is present from the CCU and there is no kickdown signal and no overtemp signal, the Klima should close the relay and the clutch should engage.

On the '85, you have very little risk of using the ice cube relay as a permanent replacement. You only lose the capability of more power when the kickdown switch closes (pedal on the floor). You also lose the capability of the relay to shut the a/c compressor down if the engine gets too hot. But, you would do this yourself.........right?

On the '86 and later vehicles with the 603 engine, the Klima is more sophisticated and is also present to prevent shredding the serpentine belt if the compressor locks up. Using the ice cube as a workaround is more risky with these engines.

Wouldn't the signal from the tach be to check engine RPM vs. compressor RPM and if there is a difference, the Klima is open and the compressor does not run?

Brian Carlton · #10 12-01-2006, 04:38 PM

Quote:

Originally Posted by riethoven

Wouldn't the signal from the tach be to check engine RPM vs. compressor RPM and if there is a difference, the Klima is open and the compressor does not run?

It would be........and that's the way the '86 and later vehicles function.

But, the '85 doesn't have a signal for compressor rpm..........AFAIK........

JimmyL · #11 12-01-2006, 04:42 PM

Yes, we have no speed sensor!!!!!!

Ask the Hitman how much fun those are........

Kynetx · #12 12-05-2006, 11:44 AM

I pulled my Klima last night to fix a non-functional fan. One of the pins on the wiring harness on the temp-wheel side had obviously overheated at some point and warped the plastic surrounding it.
I pulled the box out and disassembled it (buttons and springs flew everywhere,be careful) and found a fried trace.
I globbed solder on the joint as a temporary fix and it's working. It looks like a primary power feed or ground. How can I fix that burned trace?

Brian Carlton · #13 12-05-2006, 11:55 AM

Quote:

Originally Posted by Kynetx

I pulled my Klima last night to fix a non-functional fan.

..........it's the CCU that lives in the dash that you disassembled.........

dannym · #14 12-05-2006, 11:58 AM

Quote:

Originally Posted by Brian Carlton

.......

4) Signal from the tach. I can't figure what the Klima does with this on the '85...................

Most AC systems will sense engine speed and kick off on over rev. I wouldn't be supprised if that's what the tach signal does. kind of redundant to the kickdown sensor.

Quote:

Originally Posted by kynetx

......How can I fix a burned trace?

You can jump over the trace with a piece of wire or you can use the stuuf that fixe's defrost wire breaks. It comes in a small bottle with a brush inside. Check your local auto parts store.

Danny

#15 03-16-2007, 05:57 PM

Sorry if this has been posted in the past, but I searched and couldn't find the info, so I did a little sleuthing with the multimeter.

This is from my 85 300TD, others are probably different...

Klima Pin 15, Socket Pin 5 - +12V when key is on
Klima Pin 31, Socket Pin 1 - Ground
Klima Pin 87, Socket Pin 7 - to compressor clutch, supply 12v here to engage compressor
Klima Pin KL, Socket Pin 10, +12V here from CC unit signals AC to switch on - this signal passes through the low pressure cutout on the recv/dryer, the high temp cutout at the same place, and the freeze cutout on the evaporator.

So, connect 15 to 87 to engage the clutch, +12V between KL and 31 is the signal.