1983 300SD door lock question - Page 3 - PeachParts Mercedes-Benz Forum

eatont9999 · #31 09-21-2012, 10:55 AM

Quote:

Originally Posted by turbozeke418

I hope this helps...if looking at this picture the terminal to the right is blue...left is yellow... and the bottom one is brown

Thanks! When I get home tonight, I'll hook mine up and see what happens.

I know I have some vac leaks somewhere in the system. I have a used set of actuators and I already replaced the front passenger one. It was leaking. It is very annoying to have to crawl around the car to unlock a door.

eatont9999 · #32 09-23-2012, 02:39 PM

I got my door locks working! It's going to be awesome when I have other people in the car.

I had the positive wires backwards, so when I locked the car, the doors unlocked and vice versa. I swapped the constant with the switched lead and that took care of that issue. The way the electrical system works is it has a constant 12v and constant ground. The switched lead is ground or 12v. If the pump gets 12v from switched, it activates the pump in one direction. If the pump gets a ground on the switched lead, it activates in the opposite direction. Power always comes from constant and the relay inside is triggered by the switched lead. Surprisingly, I only had one bad pod in the front passenger door which I had already replaced. All doors and the trunk work. The fuel tank door does not but it needs to be adjusted because the pin is getting caught before it can lock the door. The vac pod does work, though.

Come on Zeke, get those door locks working; you'll love it!

turbozeke418 · #33 09-23-2012, 04:03 PM

Id love to. Im stuck now and no clue where to go.

eatont9999 · #34 09-23-2012, 11:56 PM

Well, if you have no vac leaks, 12v constant, ground and 12v switched, then you have a bad pump. In your case maybe two bad pumps. Can you bench test them to see if they turn on and pull a vac, etc?

eatont9999 · #35 09-24-2012, 12:05 AM

Oh, by the way, my pump is completely different from yours. The blue wire is the switched wire in my car. Make sure it is +12v when you turn the key one way and 0 or ground the other way. When the key lock is in a neutral position, you may see less than half a volt ambient on the blue wire. It picks up residual potential until it is grounded. Turn the key in the other direction and the meter should read 0v as long as grounds are good.

turbozeke418 · #36 09-28-2012, 08:00 PM

Problem fixed. I bought another unit for the trunk and everything now works.

seebeexee · #37 10-06-2012, 09:12 PM

Quote:

Originally Posted by turbozeke418

Problem fixed. I bought another unit for the trunk and everything now works.

I'm glad you got everything sorted. I've been monitoring this thread, because our symptoms are (were) identical. unfortunately, I have an extra issue... I'm hopeful someone in here will see this and help.

I bought my '84 300SD a month ago, and there was no pump in the trunk, so I got one from the junkyard.

My vacuum circuit is good (tested with a MityVac), the driver's-side door lock switch is good and sends the correct signals to the pump while locking and unlocking with the key, (Should I get the same results from the passenger's door, because I don't? My pump is good (bench tested with 12V power source in both directions) but my voltage from the connector at the pump is low. Instead of an alternating 12V on the blue and yellow wires, I only have 3.25V at any time, which is not enough to activate the pump.

Any suggestions anyone about why my voltage would be so low at the pump connector? Sorry to hijack the thread. I hope it's OK since it appears the original poster's issue is resolved.

Thanks in advance.

turbozeke418 · #38 10-06-2012, 09:16 PM

No problem. Hopefully someone here can't figure that out for you.

seebeexee · #39 10-09-2012, 08:06 PM

Well, I figured it out and I thought I should share.

I was only getting 3.25 volts at the pump, so I checked the fuse. The connection was not good, and I'm surprised it was supplying any voltage to the pump at all. I took out the fuse, wiped the connector and fuse with some Scotch Brite and when I put the fuse back in, I heard all the door locks pop up (since the driver's door was unlocked).

It was nothing more than a poor connection because the fuse was not blown.

eatont9999 · #40 10-28-2012, 11:30 PM

Update on mine as well. I pulled a pump and the wiring from the junk yard and hooked it up. The locks all work as they should but when I unlock the driver's side door, I have to fiddle with the door lock before the pump gets the signal to open the rest of the doors. I think the switch in the vacuum pod is having an issue. I plan to replace the pod with a spare and or check for any wiring breaks. I think the wires are OK, though. The doors always lock.

mrwcash · #41 10-31-2012, 06:02 PM

So I have been trying to fix the locking system on my 82 300SD for about a week. I located a leak in a pod and replaced the pod and the system seemed to work fine. The locks lock and unlock and the pump stops when the pressure is reached. The problem is after a period of time the pump will not start to lock or unlock unless I disconnect and reconnect the power then the locks work fine again for a short period of time. When there was a leak the pump would run for a longer period of time due to it not reaching pressure then shut off and not operate unless the power was disconnected and reconnected. I believe this function was some relay to shut off the pump and keep the battery from going dead. It appears that the relay is still turning the power off to the pump after a period of time even if the locks are operating and the pump stops when it reaches the proper pressure during the unlock and lock cycle. Any ideas if there is a relay and is it part of the pump or ? Thx

eatont9999 · #42 11-02-2012, 01:50 PM

I replaced the driver's side pod last night. The door locks work properly now in both directions without fiddling with the driver's door lock.

mrwcash,

This may not be the same situation as you but I noticed times where the pump would become unresponsive and not get a signal. It turns out it was related to my driver's side door lock pod. I guess the contacts inside were worn. However, unplugging and plugging the pump back in did not make it magically start working. I had to fiddle with the door lock to get the pod to send the signal.

mrwcash · #43 11-08-2012, 06:42 PM

I bought a new pump off ebay for $20 and everything works. There must have been a relay in the old pump that was shutting the power off to the pump after about 45 seconds even thought the pump stopped. Of all the luck the central locks on my E320 just stopped working in the last couple days............