OMP

Hi.
I have ths annoying ticking sound ( sounds like air solenoid going crazy opening and closing, pretty much like a relay sound) in the Climate Control Box ( the one with the vaccum lines and solenoids) which happens even when the Head Unit is turned off. It is not full time, it is just from time to time. I mean, there is no any frequence, itīll sound for 2-3 minutes, then stop, then come back again after 5 and tick for 1 minute, then 4 minutes, and so on.

This is happening in my 200 20V.

I have already tried at least 2 or 3 different Climate COntrol boxes as well as, at least 4 Head Units known to be good, as they were also tested and working normally in my 200 10V.

It is being there for some time. Anyhow, the mechanic told me that when disconnecting the Head Unit, the ticking will stop, and connecting it back, it will start ticking again.

So, our guesses go to the fact that there is "something" that is coming TO the Head Unit that is sending a bad signal or something to the control box.

I have the full electrical diagram of the Climate Control, but it looks like a death labyrinth as it has all the possible conections in it.

So, is there a way of having what are the INPUT signals ending in the Head Unit?
If not, being turned off, what would be a possible signal going into the Head and then, then head sending one to the box??? It does puzzle me a lot!!

Thanks

yodasfro

It's possible to check the fault codes on the CC head unit. Your fault is likely something with the vacuum operated flaps. Could be a vacuum leak could be the vacuum lines are not connected properly. One of the two vacuum units for operating the flaps may be broken or like I said the vacuum lines are not connected properly or you have a vacuum leak somewhere in the system start at the check valve in the engine bay. Also a bentley manual would help you diagnose things a little better rather than just throwing parts at and hoping it fixes the issue.

OMP

Hi Yoda.
Thanks for the reply.

But the strangest thing is that this is happening when the system ( HEad Unit) is in OFF.
I cannot check codes as on eof the relays ( the one for the compressor ) is by passed as when the ticking happens, itīll switch on the compressor and vent in speed 1.
So, it was bypassed to avoid the on-off situation ( which does it together with the ticking in the vaccum BOX)....
So, itīs a bit of a challenge.

You talk about ONE OF THE TWO vaccum units. Where/what is the second one? I know the one under the glove box....Any other Unit managing vaccum? Where would that be?

And, when the system is OFF, is there anykind of vaccum management in there? Is the system doing anything? My biggest puzzle for us is that this is happenning with the system OFF ( it also does it when itīs on), but biggest question is about the system doing it when it is OFF!!!

Would a vaccum leak do something like this? Although even with the ticking coming from the unit, climat control does work and does all its functions....although it is true that I keep seeing the "EXT TEMP" flashing for some moments when starting the car.....

I do have the Bentley but it doesn't show the UNIT signals for the head units.
We still think it is "something" that is coming to the Head Unto that is sending some strange signal to the vaccum box.....as like said, when disconnecting the Head Unit, it doesn't do it anymore....

Thanks

yodasfro

Page or section D8-200-1 in the bentley volume # 2 shows the vacuum units they are attached to the blower box. Still think it could be a vacuum leak and the a/c programer is trying to compensate somehow. Is the fresh air flap on the evaporator box functioning there is a line running to it inside the box. The flashing light is telling you there is fault in the system check the faults on CC head.

OMP

Thanks.
That is one of the ideas we have.
We are thinking that even in off, the system has vaccum and it is trying to keep the recirculating flap shut (or open, whatever it has to do).
But for what I recall, the recirc flap was working OK ( a while ago). Will check that.

Now, however, we came up with another puzzle. Again, with the HEad Unit pluged, the ticking in the air box together with a relay ticking below the steering wheel.

So, the mechanic took off the relay and it is a relay with PN 4H0 951 253A. Looks fairly new. And it is installed in position where it says "IRA Relay".

We are much puzzle on this also. What happens is that:
- Vaccum box wil tick when the Head Unit is pluged as well as the 4H0 191 253A relay in the fuse box.

- When disconnecting the HEad Unit, none of them will tick.
- When disconnecting the Vacuum box, the relay will still tick ( With Head Unit pluged)

- When disconnecting the relay ( Head unit pluged), the vacuum box with tick

- So, now we are in the psotion where the Head Unit, somehow, is sending some signal "somewhere" which makes the ticking......

Still, we are much puzzled by that strange relay ( the 4H0 951 253A) as for what I have read, it is used for newer cars for Air suspension, some other uses include intensive washer ( which my car has), or even some sort of fuel pump ( on VW Passat).....So, we are very mich puzzzled by this.

Climate controls codes I cannot run thru them as since there is a by pass on the relay for the aircon, codes will not chow a clean system as it is already by passed....

SO, the challenge is to know why with the Head Unit pluged the is a signal going to the vaccum box AND to that strange relay.....It seems that is a generic relay but donīt know what does it do, as all functions related with the a/c as it is, work.....and donīt know which one was replaced by this one either ( that could give us a hint)....

Any idea on what IRA relay it is used for?