Klima > Ice Cube - Not Working - PeachParts Mercedes-Benz Forum

BrierS · #1 08-23-2004, 12:53 PM

Though I am going to check my connections again (3rd time) the replacement of the Klima with an Ice Cube is not working on my '87 300TD. A fuse jumper wire from #5 to #7 makes the compressor engage yet when I put my Klima replacement in, the compressor would not engage. Any thoughts on this one would be greatly appreciated.

BrierS · #2 08-23-2004, 05:03 PM

Following the MB Service Manual ACC for Model 124 I ran the sequence of tests "Checking compressor cutoff if the electromagnetic coupling of the compressor is not switched on." Each test returned nominal values. That brought me to "Renew control unit (N6 - Klima)." That being said, again I put my Ice Cube for Klima replacement in. No compressor engagement. Remember, in the testing sequence terminals 5 & 7 are jumped and the compressor did engage.

Ideas on what to do PLEASE.

BrierS · #3 08-23-2004, 05:33 PM

Still moving on with this project I found -0- volts at terminal #4 of the Klima socket with the engine at idle and appropriate switches set. According to the SB link, voltage should be battery until full throttle. If I am heading in the correct direction, this may indicate that the full-throttle micro-switch is closed all of the time. If it is in fact bad, would this explain why the Ice Cube relay replacement for the Klima isn't working for me? Is there anything short of replacing the micro-switch I can do?

jcyuhn · #4 08-23-2004, 05:42 PM

Can you post the wiring layout you used to build your Klima replacement? Which terminal on the car is connected to which terminal on the ice-cube?

I doubt the full throttle micro-switch is the problem with your ice-cube bypass. It would take multiple ice-cube relays to include the full throttle shutoff logic into the Klima replacement. There's a reason MB used electronics...

- JimY

mbdoc · #5 08-23-2004, 05:52 PM

Tha A/c panel must send a GROUND signal to the Klima relay for the compressor to engage. That signal comes in at pin 10 of the klima relay.

Also the tachometer must work & the RPM signal must come to the klima relay as well.

There is also an overheating switch on the engine that can stop the compressor from comming on. TRY disconnecting that switch to see if the switch is shorted.

Also on the accelerator linkage there is a limit switch that cuts off the compressor durning acceleration, try disconnecting that switch as well.

BrierS · #6 08-23-2004, 06:16 PM

JCYUHN
Okay . . . the wiring layout for my Ice Cube (replacement for Klima) is #1 > #85, #10 > #86, #5 > #30 and #7 > #87.

M.B.DOC
The ground coming in at #10 is present i.e. battery voltage with #10 (-) & #5 (+) reads battery voltage.

Tach is working properly as is speed sensor test.

The emergency cutout temperature switch results in < 1 volt when tested at #5 (+) and #12 (-).

I am uncertain if you mean the micro-switch for full throttle as to your reference to the throttle linkage. If so, where I should be getting battery voltage at #4 of the Klima socket I get zero. Unplugging the connector at the bottom of the micro-switch does not change it one way or the other.

I am wondering if the lack of battery voltage at #4 is indicating that the micro-switch portion of the circuit is the problem. If I understand it correctly, when it operates correctly there would be battery voltage until the micro-switch passes full-throttle and cuts the compressor for extra hp. This is where I am stuck . . .

BrierS · #7 08-25-2004, 11:25 AM

Arthur,
I re-ran the series of test at the Klima socket because I remembered the last test involved the speed sensor and I was uncertain of the result. According to the service manual testing the voltage (in AC not DC) at terminals 1 & 2 should give > 3.8 volts at about 750 RPM and should increase the voltage as the RPMs are increased. I just measured it again and confirmed what I had thought I found the first time. The voltage starts at or about battery voltage (hard to tell since I am in AC voltage mode) and stays that way through out the RPM range. Any idea how I can safely bypass the speed sensor?

Arthur Dalton · #8 08-25-2004, 11:44 AM

The only way I know is with the ice cube relay.
The problem, as I have mentioned , is some PB units feed power to the klima and some ground the klima. [ at pin #10]
So which relay is used depends on the PB switching.
If pin 10 is a switched ground [which I think yours is, as you stated neg reading ] then the relay uses pin 10 for the ground side of the relay coil.
If the PB #10 terminal is a power feed from the PB , then the ground for the relay coil is grabbed at pin # 1.
So, 2 different systems that will require different relay internals

here is a link that MBDOC has post in regards to rpm bypass.
I am not fimiliar with that circuit have no info to check into it..

A/C RPM sensor bypass

jcyuhn · #9 08-25-2004, 12:36 PM

Steve -

Have been too busy to respond of late, apologies for the delay.

I believe your ice cube bypass is improperly wired. Arthur has identified the correct solution in his text, but the instructions he has quoted from a previous post apply to a gasser; diesels, for some mysterious reason only understood in Stuttgart, operate differently. I have successfully built and used an ice-cube bypass for my '87 diesel, though it has been a few years.

In general, a gasoline 124 sends +12v to pin 10 of the Klima as the signal to operate the compressor. Your diesel grounds pin 10 of the Klima socket to signal operation of the compressor. Use your DVM to check voltage between pin 5 & 10 with the a/c switched off, then on. I expect you to see indeterminate voltage during the first test, and a solid 12v on the second.

If so, modify your ice cube bypass as follows: pins 85 & 86 (the relay coil) connect to pins 5 (+12v) & 10 (PBC ground signal) on the Klima socket. Not sure if it matters which Klima pins are connected to which relay pins. If it doesn't work, try swapping pins 85 & 86 on the relay - some relays are sensitive to the direction of current flow.

Pin 30 on the relay is also connected to pin 5 (+12v) on the Klima socket. Pin 87 on the relay is connected to pin 7 (compressor coil) on the Klima socket. Pin 87a on the relay is unused.

So if it is all working correctly, when you push the a/c button in the cabin, the PBC grounds pin 10 of the Klima socket. Since pin 85 of the relay is now grounded, and pin 86 is connected to 12v, the relay activates. This connects 12v at pin 30 of the relay to pin 87 of the relay, which then sends +12v to the compressor clutch. The compressor switches on, you get cold air and a smile on your face.

A couple of notes on the bypass circuit. You will of course lose the RPM comparison compressor cutout circuit. Whether this is a bug or a feature I will let you decide. Having had a compressor seize up while crossing the west Texas desert, I rather like it.

You will lose the high temp cutout circuit. The Klima relay shuts off the compressor when engine coolant reaches 115C degrees. Of course, you can monitor the coolant temp and take care of this manually. Shouldn't ever happen in a properly operating car.

You will lose the full throttle compressor cutout. So you stay cool while passing, but it takes longer to pass. You can always switch to E/C before accelerating around slower cars.

Finally, the transmission kickdown will be disabled. At higher speeds the car will no longer drop into 3rd gear when full throttle is applied. You'll notice the Klima relay is actually labeled "Klima+Kickdown."

I ran the ice cube bypass for a few months, but decided to replace it with a fresh Klima once things were sorted. I had multiple problems triggering the compressor cutout: excessive air gap on the compressor clutch (due to normal wear), plus grease and oil on the compressor clutch surfaces. These two problems caused enough slippage to trigger the cutout circuit on the Klima relay. After fixing these issues, I reinstalled the original Klima. The compressor no longer cutout, but would switch on & off in a rapid, random succession. I ordered a new Klima relay, and all has been well since. I think all that diagnosis and work was in the summer of 2000; not exactly sure.

Guess my point is this: Klima relays do go bad. They do more than just switch on the compressor, so I see the ice-cube bypass as a temporary/diagnostic fix.

My $.03 (long post...)

- JimY

quick edit: Here's a link to a site with ice cube schematic & explanation: http://www.teamrocs.com/technical/pages/relay_basics.htm

BrierS · #10 08-25-2004, 09:05 PM

jcyuhn,
Did you check Arthur's photo sketch? If you were in my place would you think he didn't like my computer (keyboard special) drawing?

Kidding aside, thanks to both of you. I got as far as attempting to check the voltage actions of terminals 5 & 10 with my TWO meters. The first one is a meter I bought about thirty years ago when I owned/operated a service station. It relies on the battery for the primary + & - leads and provides a voltage + clip/probe and one for testing ohms. Being digital, I tried to use the negative cable on terminal 10 but the meter won't work that way. So I hooked it up to the battery as I normally would and individually tested 5 & 10 just to see if voltage was present. I was surprised to find 0.34 volts at 10 while battery voltage was at 5. Next I used my little muti meter knowing it would not allow for small voltage readings. However, it does work directly with two probes. I checked with 5 (+) and 10 (-) and got the desired results switching the PB Controls on and off of AC. I will need to redo my ice cube wires tomorrow since my old bulldog suddenly showed signs of distress. He has a bad heart and has had three conversions. Being my best pal his last days find me staying as near as possible (hated to travel to Manchester today). Sorry for the long explanation yet I wanted to let you know I really appreciate the help and also that I am moving as quickly as possible to follow the advice. By the way, ultimately I want to find the problem and go back to the Klima. I am not so concerned with the risk of undetected compressor failure since I am very accute to any changes in noise and other operational issues. Kickdown is nice and the extra power under full throttle likewise, however in the meantime AC would be better.

I need to find and read (I have the CDs, MB Climate manual, and Haynes) the procedures for checking the compressor clutch gap and acceptable cleaning methods. Typically I use electromotive cleaner for anything electrical but I am not certain if it is advisable on AC (never watched any of my mechanics working on AC when I had my station). I love doing this stuff and wish I had another eight weeks straight of vacation (just finishing my eight) to keep sorting. Okay, too long. Its been one of those days and Brier (bulldog) isn't up to eating so he certainly doesn't want to listen/read my ranting.

I'll keep you posted and thanks again.

jcyuhn · #11 08-26-2004, 10:31 AM

Being a "dog person", I sure understand your priorities.

Checking clutch gap is easy - just use feeler guages such as for valve adjustment or spark plug gapping. The clutch air gap is supposed to be 0.50mm, plus or minus some small amount that I cannot remember.

There are lots of options for degreasing the clutch. Brake parts cleaner would be one. Think I used a citrus degreaser intended for bicycles, rinsing with water. It's not rocket science, you just need a method to get it down into the clutch gap.

- JimY

BrierS · #12 08-27-2004, 05:34 PM

Back at it . . . or almost. I toasted my spare ice-cube so I have four on their way. Additionally, I found a Klima for $40 and that has been shipped. I do intend to eventually find all of the gremlins and use the Klima the way it was intended.

I also had another dilema while testing. I had two multi meters and now I have a third. My digital ran from the vehicle battery so when I had to use one Klima socket for ground and another positive I had to switch to my little needle meter. It wasn't designed for automotive use and the voltage scale imposes real limits (10 volts, 100 volts, etc.). So today I went to Sears and purchased a relatively inexpensive digital that gives me more meter than I need. Actually, since it has the temp probe I can monitor my ACC temps from the vents once I get the ACC operational again.

While I'm waiting for delivery of my relays, I want to keep testing. An area I am uncertain of (there are still many of those) is the air gap on the compressor's clutch. First, if by jumping 5 & 7 at the Klima socket engages the compressor is it safe to assume that the air gap is approximately correct? If I do need to check it, is there a nut to remove at the front (after loosening the belt) that will provide access to the clutch components?

I'll keep you posted.

P.S. Brier, my bulldog seems to be doing better. He is snoring up a storm at my feet as I type. I think the brief ride in the MB yesterday did his spirits some good. He still prefers the '77 VW 7-passenger bus since he can stretch out and snore. Just over eight years old and with a life expectancy (according to the breed) of 8-10 he is probably doing as well as I can expect. What big babies these four-legged family members can be.

jcyuhn · #13 08-27-2004, 08:24 PM

Steve -

Didn't you post the air gap question in a separate thread? I think I answered there. Either that or I'm hallucinating again. Wouldn't be the first time.

Anywho, long and short is no, jumping the Klima and having the compressor engage is no guarantee it'll work with a good Klima in place. Mine worked fine with an ice cube relay, but would cutout with a Klima. Check the air gap and I bet you'll find it to be 0.8-0.9mm. That's flaky territory - the compressor is capable of working OK, but there's enough clutch slip to trigger the Klima speed comparator circuit.

Setting the air gap is pretty easy. Remove the 10mm nut which retains the front plate of the compressor. You need a special puller to remove the plate. It's nothing fancy, most McParts stores will rent/lend you one - I bought mine for ~$20. Space may be tight between the clutch plate and the radiator. With the clutch plate removed, you'll find one, or two, or maybe three small washers on the compressor shaft. These are spacers. Try removing one or two of them to see which result gets you closest to 0.50mm. Don't go below 0.35mm - that's minimum spec. If you wan to be really obsessive about it, your local auto a/c place will sell a kit with a variety a spacer rings so you can set it just right.

Assuming you can get the clutch plate off the front of the compressor without pulling the radiator

it's a 15 minute job.

Good luck,

- JimY

BrierS · #14 08-28-2004, 06:57 PM

I am attempting to pull the compressor clutch in order to check the air gap. How in heck do I hold it from turning so that I can loosen the 12mm nut?

jcyuhn · #15 08-29-2004, 12:27 PM

You know, I can't remember what I did to hold the clutch plate from turning. I don't think the 12mm was all that tight when I worked on the compressor. How about a strap wrench, like for a spin-on oil filter?

BTW, here's a link to a site which explains rebuilding a nippondenso compressor. Most of it isn't relevant, but some of the photos & steps might apply to your task. http://www.pelicanparts.com/techarticles/911_Nippondenso_rebuild/911_Nippondenso_rebuild.htm

Best of luck,

- JimY