Klima Relay Options
 

Hi all,

I have been researching the Klima relay and my options for how to deal with it. When I pulled the cap from my klima relay, I saw this:
http://i83.photobucket.com/albums/j3...MG_0603-01.jpg

OK, fine, I know I have an older engine in there, and I just fixed the tach for it today. But, because I "fixed" the tach to an older style setup, my EGR brain is not going to respond correctly, and I will have an issue with the Klima Relay anyway.

Ive obtained the most info from here:
http://www.peachparts.com/shopforum/diesel-discussion/172032-klima-basics-missing-forum.html

But still am not sure about my setup. So I have some questions and then some options for the sourse of action.

Since Linking 87 and KL sends the PBU compressor signal to the compressor bypassing all Klima interrupts, and since apparently the refrigerant low pressure switch in an 85 is between the Klima and the compressor, it seems that if I jumper over the klima by sticking a fused wires between the right holes, then all should be well. Right?

I am worried that if I jumper the Klima, that the AC will not cycle correctly. Is this a real fear, or should the "logic" that determines the cycling of the compressor be based on some other set of switches that is irrelevant to the Klima? Does anyone know if the 85 cars used a different ac compressor from earlier cars? Depending upon the connectivity via the Klima relay, it may not matter anyway. It seems that all 300D card used an R-4 compressor and that there is no real difference.

So, options... Of course my first option is to jumper past the Klima relay and hope for the best... However, I have to wonder about these unknown connections found under the hood:
http://i83.photobucket.com/albums/j3...MG_0607-01.jpg

http://i83.photobucket.com/albums/j3...MG_0601-01.jpg

And if they have anything to do with the AC and Klima.

Now, if I just jumper it over, per my research, the only things that Ill loose are as follows: the capability of more power when the kickdown switch closes (pedal on the floor); the capability of the relay to shut the a/c compressor down if the engine gets too hot.

Neither of these are earth shattering... but of course this means that jumpering the Kima relay must work to make the AC system operate as it did in 84 and earlier cars. Is this a safe bet?

Now, option #2. Say I obtained a new or good used Klima relay. Could I modify it such that of the three functions it protects for, i.e. 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.

Could I somehow modify the klima such that the tach signal (not present) is always set in the relay to be correct and so the AC can operate? This way, assuming that all the rest of the wring is intact, I still get the low pressure protection and the kickdown shutoff conveneince.

Is this possible?

Finally, option #3: assume that all the connectivity to the Klima other than the tach signal is still in tact. Also assume that it is not smart/possible to modify a working klima to operate the rest of its logic without the tach signal. Could I then buy a different relay, use the pins from the klima setup, and have the relay operate such that if the CCU calls for cold air, it closes unless only two options, kickdown switch or temperature signal? That is, use a relay with one less option to cause it to open. I assume that with a single different relay (not necessarily drop into the existing holes) or a set of simpler relays wired up some way, I could gain this functionality.

Do I have basis, or am I just spewng out ideas that will never work. Any ideas or comments? I am fine with doing whatever, so long as I gain working AC. I just worry about the fact that I have a replacement engine, and its effects on the operation of the Klima functions, the EGR computer's effect on the AC and Klima setup, etc.

Any ideas or suggestions would be most appreciated.

Thanks!

JMH

get rid of the egr.....

I have the kit... the one that the old timers on here all bought some time back, which seals of the EGR. I didnt install it back in 2004 before my 83 got smashed. It is on my list of projects. Right now I have the 83 setup EGR in my 85 car due to swapped engine, and the EGR is disabled via standard methods...

Thanks,

JMH

You have correctly identified the function of the Klima on the '85. All will be well if you bypass the Klima with jumpers and the cycling of the compressor will be unaffected. As you mentioned, you lose protection from overtemp and you lose the capability to dump the compressor when the kickdown switch closes.

It's a guaranteed bet. Jumpering the Klima to remove it on the '85 won't affect the operation of the a/c.



I don't understand what you want to modify on a perfectly good Klima? If the Klima works properly, you get the protection you seek and the dropping of the compressor during kickdown.

Again, I fail to see the need to reinvent the wheel.

Quote:
Originally Posted by JHZR2

Now, option #2. Say I obtained a new or good used Klima relay. Could I modify it such that of the three functions it protects for, i.e. 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.

Could I somehow modify the klima such that the tach signal (not present) is always set in the relay to be correct and so the AC can operate? This way, assuming that all the rest of the wring is intact, I still get the low pressure protection and the kickdown shutoff conveneince.

Is this possible?
I don't understand what you want to modify on a perfectly good Klima? If the Klima works properly, you get the protection you seek and the dropping of the compressor during kickdown.

Quote:
Originally Posted by JHZR2

Finally, option #3: assume that all the connectivity to the Klima other than the tach signal is still in tact. Also assume that it is not smart/possible to modify a working klima to operate the rest of its logic without the tach signal. Could I then buy a different relay, use the pins from the klima setup, and have the relay operate such that if the CCU calls for cold air, it closes unless only two options, kickdown switch or temperature signal? That is, use a relay with one less option to cause it to open. I assume that with a single different relay (not necessarily drop into the existing holes) or a set of simpler relays wired up some way, I could gain this functionality.
Again, I fail to see the need to reinvent the wheel.


Well, the problem is this... The Klima will not work properly if everything that Ive found in my research is correct. Apparently though it is unknown why an RPM signal is sent to the Klima, it is necessary for its correct operation. However, since my 85 car doesnt have an 85 engine, it can't get the correct signal through he EGR computer and sent along as a normal klima and egr relay equipped car would.

Thus my problem...

My angle is that it would be nice to have the temperature protection and disengagement at kickdown that was designed into the system. The problem is that if I just jumper around the klima alltogether, I loose both of those options.

Is it a biggie? Not really, but it seems that there would be a way to solve the problem with either a klima relay mod, or a different relay being used. Relays are relatively simple things from what I know.

I cannot imagine it would be that tough to get the protections and conveniences that I desire with a slight mod.

Let's assume that the Klima is set to close for all times that the ACC calls for cold air, except for four cases - temperature irregularity, presure irregularity, kickdown switch is closed, and rpm signal is not present. It seems that these are the four Klima opening faults that it is designed to disengage the AC system for.

So, this means that the relay is set up in some way such that all is well unless those four faults have a 'signal', which defaults to making the klima open. So, there would have to be a way, jumpering or otherwise, where the 'correct' signal for the RPM inpt, could be forced inside the relay. This way the relay always thinks that the RPM signal is correct, it is fine, and so the klima relay will never open due to tachometer input.

By bypassing the RPM fault in the klima, the relay goes from having four protections to having three This is my hope and desire - to maintain the protections designed into the klima system without having to have the correct rpm input signal. My two options to gain same are depending upon if it is thought to be easier to modify a relay that has four potnential fault inputs that would cause it to open, bypass one (rpm input) to maintain the other three, or if it would be smarter to find another relay that is designed to only have three potential inputs that would cause it to open. There are all sorts of relays out there, and Id guess that a bit of research would locate the right one.

Any thoughts???

Thanks again for considering my crazy idea!

Best,

JMH

OK, I see the issue.

Absolutely, if you can determine how the Klima uses the tach signal, and can somehow bypass that tach signal so that the Klima ignores the tach, it would be a perfect solution.


That might take some heroic efforts, however, because you don't know the internal schematic of the Klima and how the signals are processed to operate the relay.

Does anybody have a schematic of the klima relay, klima system, or the AC system in general? Des anyone have a broken klima relay? Id like to open it up and see what I can find out. Even a full disclosure of what each of those pins do would be great.

Thanks!

JMH

I know this is an old thread but have you done anything with the Klima? AC in my 85 was working nicely in the 90-degree heat yesterday and all of a sudden stopped. Checked the compressor, clutch was not engaging. Checked the pressure switch on drier and it was closed i.e. sufficient pressure. Finally gave to Klima a little ***** smack and the compressor clutch pulled in and AC working again. I am thinking along the same line as you and would like to bypass the Klima.

You can bypass Klima with an ice cube relay, losing the protections it provides. My '85 300D-T was so bypassed when I got it. I eventually found a Klima for it and restored proper operation.

For funola's problem it may be possible to open up the package (remove sealant, pop off the cover) and carefully clean the relay contacts. That may restore proper operation.

As for the internal schematic of Klima, I've never seen one. The engine speed portion simply keeps the a/c compressor's clutch from engaging until the engine speed gets up to at least 500 RPM. Modification would involve some reverse engineering; in theory one could re-bias the appropriate transistor to keep it ON all the time.

Jeremy

The Klima provides two functions on a diesel:

1) it compares the rpm of the engine (from the crank sensor via enine electronics) to the rpm of the compressor (from the speed sensor on the back of the compressor) This is to save you from being disabled by a torn belt. Workaround: toss a spare belt into the trunk.

2) For some unknowable reason, it controls power to the kickdown relay.

So thats what it does, and now you can assess the risk of bypassing it.

Which diesel are you referring to? I have an 85 300D which is the only year W123 with a Klima relay. Here is the W/D. #28 is the Klima. I do not see an RPM input going to it from the compressor.

http://i323.photobucket.com/albums/n...300D/Klima.jpg

Sorry, haven't had that car for a long time...

That is the correct diagram for the '85 300D-T, same as the one I used to have. Since a/c has its own belt in the 617 engine there is no speed sensor. Worse case if the compressor freezes you cut or otherwise remove that belt.

The kickdown switch is part of the mix because if the engine's RPM is at the high end (as measured by the crank sensor and Klima), flooring the accelerator (hence pressing on the kickdown switch) will do nothing—the transmission will stay in the gear it's already in. This would be somewhere around 4000 RPM, I think.

This is one more safety precaution you lose when bypassing Klima. Note that pre-1985 cars didn't have Klima and yet we survived so you probably will too.

Jeremy

Per the schematic, it looks like the Klima supplies switched +12V (via some kind of on/off logic) to the kickdown switch, to prevent actuating the kickdown solenoid in the transmission under certain conditions. For example, if RPM is below lets say 1000 RPM and you actuate the kickdown switch, power is cut to kickdown switch= no actuation of the kickdown solenoid. I may be able to test if this is true with a test lamp on pin 6 and varying the RPM.

Strange, there was a reply from Mxfrank but it seems to have been immediately deleted by him. I am copying it below from email.

I measured between pins 5 and 6 of the klima and it was shorted together. However, if I push on one of the 2 relay contacts, 5 and 6 opens up. So power for the kickdown solenoid is controlled via a relay in the Klima. Mxfrank, you have a 190D as I recall and not a w123 diesel? Maybe the Klima in your 190D works differently?

"Good imagination, but it's not that complicated. The only thing controlling kickdown is the pedal switch. The Klima supplies plain old 12V to the switch. That's all, no logic, no conditioning. On the gas cars, the function is supplied by the fuel pump relay. I guess they want a power source that's related to the engine actually turning.

I'm not sure if there are any fuses on the kickdown circuit. I can tell you for a fact that the trace on the Klima board will turn to smoke if you short the solenoid. It wouldn't be the only case of Bosch using an expensive part as a fuse."