An idle up Solenoid

Hello Eric,

The 230GE did not usually come with factory fitted A/C systems unless specifically order by the original customer. Is your a factory fitted unit or an after market fit? 

If it is an after market kit; what make is it? In the UK it was Diavia a/c systems but that company has long time been dissolved or taken over.

Finally, what is your base idle speed reading at idle without using A/C or any other loads?

I am sorry to disagree with Arnie on this, the part you are looking for is called a switch over valve. Arnie has rightly shown an idle control valve but this is for the base idle control for the engine idle. It cannot sense any load bearing auxiliary units such as a/c load.

Now I say this with questionable confidence but If you Google this part no:  A 001 540 86 97 and select the tab for images you can view the solenoid valve as to what it looks like. 

Alternative URL:

http://www.partsbase.org/mercedes/cross-230-ge-461-218-395-54-28108-001-...  

go to this site and there is a picture showing location of the change over valve. 

The idle speed valve is just a thermostatically controlled valve that adds allows air to bypass the throttle.. the ECU must be increasing fuel injector volumes at the same time to increase the cold idle speed.

Newer ECU would have a target idle rpm with a proportional/dithering solenoid controlled air valve.. and it would increase the air supply (and fuel) to maintain the idle. Hence A/C would cause an rpm drop but the ECU would drive the air by-pass (or idle speed control valve) and fuel injection volume to regain the target rpm.

As you have an older system.. there must be a method used. My bodge method would be to put a suitable resistor into the water temperature sensor which is switched in by relay when you turn on the a/c. This would trick the engine into thinking it is still cold and so increase fuel injection volumes. At the same time you would need to energise a solenoid operated air valve to add air. Hence you would have more air+fuel = idle speed/load capacity of the engine would rise. Both resistor and air valve would need to be variable so you could tweak them.

Search brings up these

http://frigosoft.cz/DIAVIA/bulletin/bulletin026.htm = Davia service bulletins an a W124 trouble shooting table for a/c

http://viapelektronika.narod.ru/olderfiles/1/291D1500670_web.pdf = Eberspacher UK bought out Davia.. and might help.

Diavia was bought by Waeco. http://www.waeco.com/en/315.php?PHPS...253f4136573351

http://www.mye28.com/viewtopic.php?t=31903 = On a 1984 E28 bmw the Motronic ECU has a pin that you connect a/c to.. but it must have an electronic idle speed control valve .. but you are on older theromstatically operated system.

http://www.mbclub.co.uk/forums/electronics/124900-diagnostics-older-mercs.html = guess you have Bosch Jetronic K system

http://www.benzworld.org/forums/r-c107-sl-slc-class/1450844-bosch-k-jetronic-overview.html = Jetronics K overview.

http://i146.photobucket.com/albums/r275/smak101/fuel_dissy.gif?t=1244775205 = flap measuring air flow to determine fuel mixture i.e. like a carburetor.

... this shows that fuel is delivered like a carburetor i.e. more air from speed bypass will automatically give more fuel. So.. you only need to add a second bypass valve which is what Rakesh/Pistonhead was pointing you to.. but that must have a variable flow control to adjust the air flow fed to that the on/off switch he points to.

The on/off valve 001-540-86-97 is shown here http://www.ebay.co.uk/itm/like/281223590049?limghlpsr=true&hlpv=2&ops=true&viphx=1&hlpht=true&lpid=108&chn=ps&device=c&rlsatarget=&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0-L&ff12=67&ff13=80&ff14=108&ff19=0

If your system worked before then it may just need that valve.. and to test then join the ends together and idle should rise.. or pull the hose that goes to the engine and pinch hose in a U so you can control the air flow.. if you should be able to control idle by relaxing the pinch and hence allowing air flow.

Hope some of that helps .. and does no hinder ..as I have no 230CE but did play on a similar Bosch injection system once (Lancia 2000HF).

Arnie post captures it very well.. and you can see the air bypass system which has two valves.. the actual by pass valve which is vacuum operated and the electric solenoid valve that pilots/turns on the vacuum supply to bypass valve. So a case of looking carefully at all the pipes on the inlet manifold and those manuals.

No, can't see anything relevant in your pics. Nice, clean engine though !.

Many a/c systems on the W460 were retrofits. The parts highlighted (43 & 11) are those that would have been factory-fitted to a Mercedes saloon of that era with the same engine. However, note that those parts were fitted to the wings or bulkhead, so may not show in your pics. If you don't have those parts, that is probably why your engine speed is not compensated for a/c load. Did it used to work before, or has it always been the same since you've owned the vehicle?

well, Eric, it's looking like your a/c system may have been a retrofit, without idle-speed compensation.

You have therefore the choice to leave it as it is, or to try to clarify what needs to be added and where, to bring it to an equivalent of a factory install. You may also need to see what signal needs to come from the compressor or a/c system to activate the ide-speed increase.

This will require a few days of research to determine the list of parts and availability, and a mechanic to do what would appear to be a relatively simple retrofit.

This diagram shows two similar systems, presumably controlled by different functions (control boxes 39 and 44). The electric solenoids are 43 and 43a.

When activated by an electric signal, the small pilot, solenoid-valve No. 43a   allows a vacuum to reach valve No.11, which causes that to open and allow additional airt hrough it and  into the intake manifold.

When activated by another electric signal,  the small pilot, solenoid-valve No. 43  allows a vacuum to reach valve No.14, which causes that to open and  allow additional air into the intake manifold.

I think the one you need is the  43a  & 11 combination as that is activated by idle-switch No. 3 and you would only want this system to operate when the engine is idling at the accelerator rest-position.

You then need to feed the accelerator limit-switch N0.3  with an electric signal (12 V) from the a/c system, It can probably be the same signal which engages the electro-magnetic clutch on the a/c compressor drive pulley. This way, the idle-speed will be increased only when the accelerator is in the rest-position and the a/c compressor is actually running.

To be sure, that you have the correct valve type (11 or 14) you should check the function of control boxes 44 and 39 on the diagram. No. 44 should be related to the a/c system. But, regardless, this method should work.

You will also require some short additional lengths of plastic pipes and T-pieces to connect into the existing plastic pipes.

I was referring to finding the labels for control units 39 and 44 from the key in the circuit diagram that you found, just to verify which circuit combination (43 or 43a) relates to the a/c system. It was just to check, but I think it's the 43a.

You will need to buy the parts you listed as well as the limit switch assembly that connects to the throttle linkage. Then, you can use the the circuit., which powers the a/c compressor's magnetic clutch to feed the limit switch as well and the rest is as in the diagram.

You don't need to find the control units in your actual car.

well, I think you can use that screw to adjust your RPM to be a little higher, but it will then always be higher, not just when the a/c is operating.

I am pretty sure that for the system to operate automatically, similar to a factory install, you will need

1. solenoid valve 43a
2. valve 11
3. short length of vacuum hose and T-pieces
4. short length of air-hose and T-pieces
5. limit-switch and its mounting assembly for the throttle

The system should be powered from the same 12v feed that operates the a/c compressor electro-magnetic clutch, and you will see a connection for this on the compressor in the engine bay, so easy to tap into.

The limit switch is item No 3 in the diagram that you found in your post above.

(Click on your web link to see the full diagram. There, it is labelled 'micro-switch' and it is operated by the throttle linkage in the engine-bay)

This micro-switch / limit switch ( No.3) senses when the throttle ( accelerator pedal ) is at its fully-closed limit so that the air- valve is then allowed to open to increase engine revs when the a/c is on. In this way the air-valve will not operate when you are driving normally. The system will only work to increase engine revs when the accelerator pedal is NOT depressed.

No, a check-valve is a one-way valve, as might be used for the vacuum to the brake-servo-booster.

You need to find an air control valve, which is operated by the vacumum controlled through the solenoid (pilot) valve (no. 43).

I strongly recommend that you take the details you have so far to your local MB parts dept, to ensure you get the correct parts.

I don't have access to parts data for older cars, such as the W123 or W124, that may have has these systems.

If you post a new request on this forum for help with part numbers, some-one like Gavin (you might also try to PM him) might be able to help, as he works for an MB parts dept.

it will probably look something similar to this, below:

The main air-flow though the large ports is controlled by the vacuum applied to the small port (pipe).

The solenoid valve( your diagram, No 43), when open, will allow the vacuum to be connected to valve (14), similar to above, which will cause valve (14), similar to above, to open, providing additional air into the manifold to increase engine RPM.

(in case you are wondering, the above valve is for a W170 and probably not the right size for the fittings on your M110 engine)

I have since found that the Microswich (No.3)  is only for fuel cut-off on over-run and you probably already have that and not required for air-condioning idle-speed adjustment.