72 Mercedes 250, windows not working? - PeachParts Mercedes-Benz Forum

Jub · #1 03-01-2015, 11:41 AM

Hi everyone,

I am familiar with window cranks, not so much automatics (72 250):

Question: all four of my windows won't go down when I push the button, it sounds like a fuse issue (or maybe a bad relay)? Anyone know where I should look (the previous owner said they all stopped working one day).

Thanks,

Jub

cth350 · #2 03-01-2015, 11:48 AM

The car has several auxialary fuse boxes. Little rectangular things mounted on the firewall mostly. Hunt those down and check the fuses. I recall the right color being red for the windows.

-CTH

Jub · #3 03-01-2015, 12:12 PM

Thanks Cth350, when I popped hood I found a blown fuse for interior lights/clock, etc. Replaced that (red 16), but didn't notice a change (although the engine was off?; wonder if they only work with engine on).

I'll hunt around firewall too

Idle · #4 03-01-2015, 08:44 PM

If you know how to take the switch out then do so and see if you have power to the switch when the key is in the run position. If not then you have either a blown fuse or a bad relay.

Check for power to the relay and if nothing then start looking in all the nooks and crannies for blown fuses.

JimFreeh · #5 03-03-2015, 02:04 PM

PW fuses (2) are on the firewall, pax side.

Above the manifolds.

Jim

ScooterABC · #6 03-03-2015, 11:58 PM

Quote:

Originally Posted by Jub

...when I popped hood I found a blown fuse for interior lights/clock, etc. Replaced that (red 16), but didn't notice a change (although the engine was off?; wonder if they only work with engine on).

Power windows will only work if the key is in the ON position (whether or not the engine is actually running). If the master switch is bad or unplugged, probably nothing else will work (like the rear door switches). But it sounds like a fuse to me.

Idle · #7 03-04-2015, 04:20 PM

As has been said many times before...

With the style of fuses these cars have they can build up resistance between the ends of the fuses and the fuse holder. You look at the fuse, see it is not blown, and wonder what the deal is.

So I just rotate them a bit while in the holder to scratch away a bit of resistance that has built up over the years. Then they start to pass current.

So if the fuse is not blown then just clean the ends with a bit of fine sandpaper and put them back it.

Clean the ends of the holders, too.

Jub · #8 03-05-2015, 09:10 AM

Thanks for the help, I plan I really sorting this stuff out next week (after the snow has passed).

First on my list is the brake leak (can see it dripping midway through the car, near the muffler area), then check fuses (already saw some blown ones in the engine bay).

I'll keep you updated on progress (with some pics).

Jub

Jub · #9 03-21-2015, 06:14 PM

Update: fixed brake line leak (hard line), using a cool trick known as compression fitting- worked like a charm. What sucks is (and what I have read), is that brake fluid is highly corrosive. So the leak was on a line right above the resonator (that other muffler looking thingy deeper under the car), and burned a hole in resonator. Not sure how brake fluid is corrosive, when lines are made of metal?

Anyway, I remember seeing a 250 with its muffler hanging out in a junk yard in MD a few months back. Went there, still there and pulled it. Should have payed closer attention to the engine bay...turns out it was a w115, and muffler is a single pipe and w114's are double. Out of curiosity I went to muffler shop...500 for custom (pass).

Also, replaced every fuse and sanded down contact points... still no electric window power. I think next I will pull out volt meter and start digging. Jim Freeh says firewall behind Pass side (saw them), gonna look there...if power, then maybe look to interior switches per Idles rec.

FYI: also, replaced headrests, dash cap, coils, plugs, plug wires, oil/trans/radiator fluid, swaped to euro headlights and the ever so lovely subframe/sway bar bushings and with spares I had laying around (car was resting on subframe-bushings shot). Awaiting front bilstein shocks, and euro front plate from holland and will re-time/sych carbs on day off this tuesday.

I'll post some pics soon as I get some time.

Jub · #10 03-23-2015, 08:32 AM

Power window mystery solved, well kind of:

So pulled out handy voltmeter, and started digging around where Jim suggested, and I found that the positive cables were pumping out power just fine (grounded it to engine block). Then I looked at the negative ground cables....to check these I put hooked up voltmeter to pos end of battery, and looked to see if I could get a reading of 12ish volt reading. The first ground cable was fine, but the second one showed no reading (bingo). So, probably some corrosion on this line which is not allowing it to function as a proper ground.

So then, I figured if one worked an other didn't, let me just bootleg a ground to test my theory. So grabbed a spare wire, and bypassed the bad ground to the good ground (see pic) and turned key, pressed PW buttons, and motors came to life! Back windows worked great, but front two windows didn't budge (although I could hear motors working). I suspect they are off track or something?

When I pull door panels tomorrow, anyone know what I should be looking for?