Electrical Gurus Please take a peek - PeachParts Mercedes-Benz Forum

greazzer · #1 10-12-2014, 04:36 PM

OK, I tinkered with the electric vacuum pump which goes in the trunk next to the spare tire well. I have determined the following for the various wires:

1. Brown is negative - goes to negative terminal

2. Red with stripe is positive - goes to positive terminal

3. The black with stripe is positive - goes to positive terminal, but it's extra since it does not need to be hooked up to anything for the pump to work

That leaves 3 wires. And this is where I become befuddled.

There's a

Green Wire
Blue Wire
Yellow Wire

I can take any one of the 3 (G, B, or Y), and depending on where the pump's polarity is, I can take the green wire, for example, and touch the positive and it blows air or it wont. If it wont, then I touch the negative terminal and it sucks air. I can then take the green wire and touch the positive terminal and it will blow air. Just depends which was touched last. You can go back and forth with the green wire, which results in a corresponding blow or suck. You can do the same exact thing with the blue or yellow wire. However, you cannot start on green, for example, and switch to blue or yellow. In otherwords, whichever of the 3 you start out with is the only one you can use to switch from blow to suck.

If you start out on suck, it will suck for around 15 seconds and automatically turnoff. OR, if you take your thumb and block the line, it shuts offs automatically also.

Here's my question: Does anyone know if there's a way to wire this pump so that is always starts and ends on suck? I have a W123 and my system only uses vacuum (suck). I want the pump to work on a simple toggle swith, turning it on and turning it off. Actually, I will be energizing the pump and the pump has an automatic shut off built inside the pump.

Any ideas?

jay_bob · #2 10-12-2014, 07:59 PM

What are you trying to do with this pump?

greazzer · #3 10-12-2014, 08:42 PM

Quote:

Originally Posted by jay_bob

What are you trying to do with this pump?

I was hoping to have it wired to an on and off switch.

Or,

have the pump always energized (it will shut off automatically when it hits complete vacuum, e.g., my thumb on the end of the line), and I would have an "emergency" shut off switch just in case.

I have the plates for the 4.15 pedal ratio and 6:1 pedal ratio. I want to get rid of my mechanical vacuum pump and go with manual brakes. I want the pump issues resolved since the manual brakes go hand in hand with the pump. My car is manual trans, 5 speed. I only need vacuum for the door pods, HVAC pods, trunk and fuel pods, and ignition and all those gizmos are not a whole bunch of vacuum. I wanted to stay with a MB part. This MB pump has its own foam rubber housing which sits incredibly nicely in the rear tire well. I have the pump mounted and I think I can tap into the vacuum resevoir with a "T".

pwogaman · #4 10-12-2014, 08:37 PM

The green, blue, and yellow wires go one each to the front doors and the trunk key locks. If the system is locked and you move one of the three wires it will start the pump to blow to unlock and keep going until the other two wires also change by the mechanical movement of the locks unlocking or until the system times out. The same is true going the other way. So if you want it to always suck, you will need to overcome the alternating logic.

greazzer · #5 10-12-2014, 08:45 PM

Quote:

Originally Posted by pwogaman

The green, blue, and yellow wires go one each to the front doors and the trunk key locks. If the system is locked and you move one of the three wires it will start the pump to blow to unlock and keep going until the other two wires also change by the mechanical movement of the locks unlocking or until the system times out. The same is true going the other way. So if you want it to always suck, you will need to overcome the alternating logic.

That makes me feel a little better. I spent a good hour or maybe even two with a lot of trial and error to figure out "what's what" so to speak. Do you know why there are 2 hot wires. The red with white stripe is all the pump needs to be energized. The black with stripe does not need to be used. The Green , Blue, and Yellow are the suck - and - blow deals. Brown was easy -- ground.

greazzer · #6 10-12-2014, 08:49 PM

Quote:

Originally Posted by pwogaman

The green, blue, and yellow wires go one each to the front doors and the trunk key locks. If the system is locked and you move one of the three wires it will start the pump to blow to unlock and keep going until the other two wires also change by the mechanical movement of the locks unlocking or until the system times out. The same is true going the other way. So if you want it to always suck, you will need to overcome the alternating logic.

Is there a way to overcome the alternating logic ... ?