KLIMA Basics missing from this forum

[Jeremy5848]

Originally Posted by es9

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.

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

If this is how the bypass relay works, it means that the compressor clutch is engaged whenever power is on?

Jeremy

[Jeremy5848]

I am pleased to report that with a used-but-good Klima relay (part 001 545 74 05) from SoCal Mercedes Parts and about 4 hours of work, I have been able to take the final step in returning my 85's climate control system to factory condition.

A PO had dealt with the Klima relay failure by wiring around it -- a simple relay that turned on the compressor whenever the climate control system was on and calling for cold air. I had to remove the extra relay and reverse all of the wiring changes that were made. One of the things I discovered was that the "abandoned" cable I found some months ago -- someone here theorized it might have been for an alarm system hood switch -- turned out to be the original wiring to the compressor solenoid.

In the beginning, the hard part was not knowing how the system was wired originally (hence my whine that started this thread). The answer, which I have uploaded here, lies in the wiring diagram and notes that the factory published in a manual entitled "Model Year 1985/Passenger Cars/USA Version/Introduction into service." This information, which is apparently unique to the 1985 model year W123 300D/CD/TD, does not appear in any other FSM of which I am aware, not even the climate control manual.

According to the manual, the Klima relay has three functions:
(1) when the engine is started, the relay keeps the compressor solenoid off until 10 seconds after the engine speed has reached 600 RPM. This "improves engine speed stabilization after startup."

(2) with engine speed less than 1050 RPM, when the accelerator is floored, the compressor solenoid is released until the engine reaches 2150 RPM or the accelerator is released. This function is controlled by a microswitch on the valve cover (I thought that microswitch was the kickdown switch -- it is not).

(3) if freon pressure is lost, a pressure switch tells Klima to turn off the compressor solenoid, saving the compressor from damage.

None of these functions work if you have a work-around relay in your system.

The Klima relay is connected to the EGR controller (that's how it gets the RPM information, I suppose) which is hidden behind the passenger's righthand kick panel. This probably means that the relay will not work if the EGR controller has failed; a clue might be loss of tachometer function. It also means that, when removing EGR parts "for testing," you want to leave the EGR controller in place and connected.

Jeremy

[Shorebilly]

...reference Service Manual Heating Air Conditioning Automatic Climate Control Model 123......

See page 83.6-605/2.....Wiring Diagram 1a Refrigerant Compressor Control.....item 13.....Relay air conditioning system.......you can trace it from there......

SB

[Jeremy5848]

Originally Posted by Shorebilly

...reference Service Manual Heating Air Conditioning Automatic Climate Control Model 123......

See page 83.6-605/2.....Wiring Diagram 1a Refrigerant Compressor Control.....item 13.....Relay air conditioning system.......you can trace it from there......

SB

It is unfortunate that the diagrams in that book do not include the Klima 617A relay. That is probably because it was one of those one-model-year-only designs (W123 1985 only). A similar relay with similar functions was also used in the early W124 cars. I don't know how long that continued -- there's one in my '87.

The relay you refer to (item 13 in the diagram) is just a power relay. It is not the "Klima" relay that I refer to. The Klima 617A relay (part 001 545 74 05) is an electronic module with two small relays inside of it. It handles only the 3.6 Amp load of the compressor's clutch. Compare the diagram I uploaded to the diagram of that "item 13" relay and you will see they are two different things.

Jeremy

[jfman]

Subscribing....

[Smith1]

Where Is the KLIMA RELAY located on a 1995 E300D?

[Chris_87_300D]

Fantastic info on this thread and forum. I spent a few hours diagnosing the problem as per Brian Carlton's great info (posted elsewhere) and the info above. Ultimately, on my 300K+ 87 300D it turned out to be the Klima relay. I'm competent in soldering and, in hindsight, the process below is what I'd do first if my A/C compressor clutch wouldn't engage because it's an easy, quick procedure (my apologies as I'm a bit long-winded). If you're not comfortable/competent in soldering or have equipment, ask someone who is to help you.

- Remove the Klima unit (which consists of at least 2 relays and multiple electronics mounted to a circuit board inside the black case)
- Carefully open it (a small screwdriver on each of the long sides at the bottom lifts the large cover off the base). Mine had no glue or sealant, I might think twice if it did since this is a rather expensive part to replace.
- With a magnifying glass, look for bad solder joints. In my case, the bad joint was where the metal case of the relay controlling the compressor is soldered to the board - bridging pins 5 and 7 when called for. This relay is one of the two small metal boxes w/ a coil and 1 or 2 contacts each, mounted to the Klima board. The joint is located very close to the bottom of the board, near the "plug". Note: In my case it was visible but it is possible that this could happen within the bubble of solder and not be visible - you may wish to resolder at each of the places where the relay housing.
- As was the case above, I'd expect that the most likely place for a bad solder joint is one of the four places where one of the two relay "housings" (which acts as part of the electrical path) are mounted to the board. This is because it is very difficult to get the large metal case hot enough when soldering (at the time of manufacture) to get good mechanical adhesion of the solder.
- When repairing, hold the soldering iron on point of the metal case of the relay that protrudes through the board and touch the solder "wire" to the side of that metal (not to the soldering iron) until it melts to a nice tidy pool with the PC board contact. This ensures that the metal of the relay case is hot enough to melt the solder and you will get a solid mechanical bond of the solder between the relay and the circuit board. It shouldn't take more that a 5 seconds or so to get it this hot - if it does, your soldering iron isn't powerful enough and you risk damaging the relay or board with the prolonged but inadequate heat.
- If you can't see the metal of the relay poking through, you may need to get the solder hot whereby it will probably move away from the "cold" metal of the relay housing and expose it. Alternatively, you may need to remove some of the solder before repairing with either a solder braid or "solder sucker".

Effectively, in my case, the solder just surrounded the metal point of the relay (without true mechanical adhesion) and, over time, vibrated enough that it carved a tiny airspace between it and the solder of the PC board. At this point the compressor clutch could no longer be engaged.

Hopefully this will help somebody - best of luck!

[rogersherwoodki]

The A/C on my 1985 300 TD wagon does not work. I have verified voltage at the relay unit, made sure the system was charged with coolant, verified that the pressure switch was working properly and that there was 12 V nominal at the clutch terminal of the compressor. I do not hear the clutch engage when it should but don't know if it makes much of a sound. I also directly jumered 12 v to the clutch terminals and did not hear the clutch engage. Still no cold. The terminals of the clutch have 3.6 ohms across them so the coils do not appear to be burned out. Any suggestions?

[Jeremy5848]

It should be possible to disconnect the wires at the a/c compressor clutch and connect two wires that you can jump directly to a battery. The polarity (plus and minus) shouldn't matter. If you connect the clutch to the battery, you should hear a click – you can do it with the engine not running so you are sure of hearing it. With the engine NOT running and the clutch NOT engaged, you should be able to spin the compressor with your fingers. If connecting 12 volts to the clutch causes it to engage, you should no longer be able to spin the compressor because it will be locked to the pulley and held by the belt. If the clutch does not engage with direct 12 volts, it must be bad. If the clutch does engage, then the problem is elsewhere. Report back with the results of the clutch test and we will guide you further if necessary. It is complicated but not difficult, you just have to check a lot of things.

Jeremy

[rogersherwoodki]

Thanks for the reply. I hooked up the clutch terminals again to a 12 volt supply (battery charger) and the clutch did not move or make a sound. The circular plate at the front of the whole clutch/compressor assembly spins freely - with voltage applied or without it. I am assuming this plate should suck in tight against the cylinder (that the pulley is connected to) to drive the compressor???

Do you know if the clutch or clutch coil can be replaced and how, or if the whole clutch/compressor assembly has to be replaced? Thanks alot.

Roger

[Jeremy5848]

OK, you did the right test, sounds like your clutch is fried. I'll defer to others as to replacing the clutch part alone. I suspect that your options will be a new compressor ($$$$) or a rebuilt compressor ($$) but maybe a local shop would be willing to replace only the clutch at a reasonable price or maybe it's DIY-able.

To help make that decision you need to know – has the a/c ever worked since you had the car? There's no point replacing the clutch if the compressor itself is also bad. If you have no idea whether the a/c works at all, you may want to get some input on what it would cost to have the system completely diagnosed before you spend any significant amount of money on repairs. If you buy a rebuilt compressor ($245.70 from ********AZ, FastLane does not offer it except as a special order, list is over $500) and then discover that you need a whole bunch of other parts, you will not be happy.

Jeremy

[rogersherwoodki]

OK. I may try to take it apart and see if there is something obvious. I read that the clutch is pressed on so it may not be easy. Again, thank you for all of your generous help.

Roger

[tankowner]

Originally Posted by Smith1

Where Is the KLIMA RELAY located on a 1995 E300D?

The Klima relay on a 95 E300D is located behind the battery. You must remove the cover located directly behind the battery (single piece of black molded plastic the pulls right out) to reveal various electrical components including the Klima. It might be easier to get to if you remove the battery first. If I recall correctly, the Klima is the most forward-sitting (closest to the battery compartment) of the bunch. The actual relay circuit board is housed inside of a black plastic case that is about the size of a deck of card - on the top will be the part number and it should aslo read "Klima/KD," - the KD stands for kickdown, since this relay controls both the klima (climate control) and the kickdown relay. When the kickdown engages, power is cut to the AC compressor to provide more power to the engine.

I replaced my Klima relay this summer and had a post on here, I will locate that link and post it here. I also took picutres that I intended to post, but I don't think I ever did - I'll post those too.

[Keebler64]

Let me know if this sounds like a Klima issue. I have searched the forums, and I keep coming back to it.

I have a 1985 MB 300SD does that qualify for the infamous One-Off model year Klima? Or was that only W123s? Anyway, here goes.

Car was working fine before changing motor mounts, prior to the motor mount R&R, the car had been sitting for a few weeks. Fast forward, motor mounts replaced, turn car owing cool. Turn the car off to go inside and think for a bit. Come back out, battery dead, no start, and fuse 11 in the fusebox is burning to the point the contact has changed color from the heat. Jump start it, can't get compressor to turn on at all, some other relays are hot, but mostly just the #11 fuse, which indicates A/C system. After doing a quick search, I pull the Klima, and everything starts on first try. I haven't gone back to do the battery-compressor test, or short out pins 15 and 31. But I did look at my Klima, all the solder joints look corroded and junky like burnt flux. As well as one of the relay's in the klima looks discolored and its missing one of the two contacts for it.

I'm open to suggestions. I'm going back tomorrow to try to figure it out and hopefully drive home.


Thank you,
Christopher Thomas

[Jeremy5848]

AFAIK, the SD got the same relay as the 123s did in 1985, they had essentially the same engine. The problem could be the Klima relay itself or it could also be a shorted a/c compressor clutch. A clutch that draws too much current could cause problems all the way back up the line to the fuse box. The clutch should draw only a few amps. I don't remember how many exactly but less than 5, I think. You can pull the 2-pin plug off of the clutch and try connecting the clutch directly to a battery. You should get a definite "click" or "clack" as the clutch engages.