power windows 83 240D - Page 2 - PeachParts Mercedes-Benz Forum

Jon J · #16 06-17-2011, 01:57 AM

Thank you. All three fuses A, B, 12, are hot. Checked cleaned and replaced.
Now I can forget the relay. moving on now to the switches. Witch of the several wires plugged into the switch(s) are the hot ones? I can then test for an unplugged connector, or broken wire. I am going to open up the doors later this week to address the vacuum leaks, but I would like to know if the switches indeed have power or not. Just because the fuses are hot doesn't mean the juice is getting to the switches. I try not to ass u me things like that. gets you in trouble don't ya know.

Jon J

Codifex Maximus · #17 06-17-2011, 02:04 AM

Quote:

Originally Posted by Jon J

I have been searching the posts trying to find the location for the window lift relay. So far it 's located,
1. In a box on the fender
2. Behind the instrument cluster
3. On the firewall above the brake booster.

There seems to be either one or two.

Is the relay ahead of the fuse or behind the fuse in the circuit?

Does anyone know from PERSONAL experience
where it is.
83 240D

I've never seen a 240D with power windows. However, I'm sure they do exist.

Remember, the following is general electrical knowledge and not specific to the car as I've not seen a 240D with power windows:

Anyway, the fact that you've tested the power at the fuses indicates that the circuit has power.

The reason to use a relay is when you've got a high power circuit(window actuators) to be controlled by a low power circuit(switches). So, probably, the engineers used a switch to activate a relay which controlled the high power circuit to the windows. This means, the switch is probably a normally open dual throw switch. When pushed in one direction, you get a closed circuit in one polarity and vice versa.

Knowing this, you could test for voltage at the switches. You'll probably have 12VDC. I believe the grounds are light brown - make sure they are not faulty. Test your switches out of the circuit to make sure they function and then put them back in the circuit and test if you have 12VDC drop across the switch when not pushed and 0 VDC after switch is closed.

Then you can find the relay and test that (probably under the dash on an early 80's W123). You'd put 12VDC across the primary and listen for a click - the secondary closing.

Do we have a wiring diagram for this model year that includes power windows?

tangofox007 · #18 06-17-2011, 02:04 AM

Quote:

Originally Posted by Jon J

Witch of the several wires plugged into the switch(s) are the hot ones?

Power to the console switches is via wires that have RED in the color scheme. As in all red, red/yellow, red/black, etc.

When a switch is not actuated, both wires from the switch to the respective motor are hot. Depressing the switch removes power from one wire and connects that wire to ground.

tangofox007 · #19 06-17-2011, 02:19 AM

Quote:

Originally Posted by Codifex Maximus

This means, the switch is probably a normally open dual throw switch. When pushed in one direction, you get a closed circuit in one polarity and vice versa.

No.

Quote:

Originally Posted by Codifex Maximus

Then you can find the relay and test that (probably under the dash on an early 80's W123). You'd put 12VDC across the primary and listen for a click - the secondary closing.

One relay, four windows. One bad relay, no windows work. One or more windows work, no bad relay.

Jon J · #20 06-17-2011, 02:39 AM

That's a big help. as long as I know how the switches work I'm good. If I have power to the switches I'll stop there until I get back home this weekend and have time to proceed. I'm working a lot of hours and don't have time to figure all of this out. I have a schematic, but the quality is so bad that it's more useful as a lining for a cat box . I have vacuum leaks in the doors so I'll be into them anyway and will test the motors at that time. If they test good I'll dive into the switches. However I should have time tomorrow to at least see if the power is getting to the switches or not at least.
The gremlins are forced into a smaller and smaller space.
Thanks again,
Jon J
83 240D
144k

81 240D
280k

Yak · #21 06-17-2011, 04:37 PM

It's difficult to see, but the rocker action pivots the tiny arrows from left to right as a unit connected by the dashed line. I.e. for the underlined RH FRONT to go down, the left-most arrow above #4 pivots to the left of the sausage and stays connected to power and the right arrow above #3 pivots off the sausage and connects to ground; so for down, at the switch 5 is hot "in" 4 is hot "out" and 3 is gnd. Up 5 is hot, 4 is gnd, 3 is hot.

Diagram is for a 300, but I presume the 240 switches function the same.

Jon J · #22 06-17-2011, 08:32 PM

I'm finally going to have time to work on this car this weekend. I've made a first things first list due to the number of things that need attention. Probably get to the switches Sunday. I have some vacuum leaks in the doors so I thought while I have them opened up I'll test the motors, and then move on to the switches. I have a pretty good understanding now of how they work thanks to all the response from this forum . Thanks again
Jon J