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Old 05-04-2009, 10:33 PM
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Join Date: Apr 2004
Location: KY USA
Posts: 2,238
My "$42.00" 380SL Keyless Door Lock Installation

Not For The Timid - '85 and below Models

Well, it was a big PITA, and it cost me more than $42 at the end of the day, but it was still worth it. I bought it because of some recent discoveries I made about SL door locks - they are very expensive to replace and they WILL wear out - but that's for another post.

I bought this $42 (shipped!) kit on eBay, and I bought it because it was inexpensive, had small, fairly sturdy-looking remotes with chromed metal edges, and had "instructions specific to my car".

Well, the instructions weren't that great. Firstly, the specific instructions I got came from some sort of a subscription website and just gave color codes (and little in the way of locations) for the wiring, and that's it. The manual wasn't very complete (no battery information for the remotes, as to type or how to replace them). Some generic instructions were given for connecting the solenoid to the lock. Although the kit had two solenoids, I knew I would need to use only one for the driver's door. I could have hooked up the other solenoid to the trunk latch so that I could remotely open the trunk (maybe, if it was strong enough), but on this car that feature is not very useful IMHO. I may, in the future, hook this up to the horn as a "car finder", but I doubt it. I can't stand cars that make a honk or chirp when you lock/unlock them.

So, I removed the door panel, and removed (very carefully) the door bag. After recovering from the horrible sight of rust (some undercoating had peeled away towards the back rear of the door) and repairing/undercoating the heck out of it, then, I was ready to begin.

The SL door locks are very clever. A small latch is moved when you lock/unlock the door, which moves rods connecting the interior door lock. In addition, a vacuum slide valve connects vacuum to pull opposing sets of diaphrams in pods in the passenger door, the fuel flap, and the trunk lock, opening and closing them. On an 86+ (very different), there is a vacuum pump that provides "limitless" vacuum and the pump is operated with an electrical switch in the door. On an older SL like this one, there is a reservoir for vacuum derived from engine vacuum that is good for about five open/close cycles with the engine off (assuming that the system is in perfectly good shape).

Where to install the solenoid is not completely intuitive. But first, some comments about the solenoid itself. The solenoid provided is a "generic" solenoid probably of Chinese origin that is found in many lower-end kits. Although it works, it isn't particularly strong.

Most systems like this have some sort of a switch or jumper for "pneumatic locks". What this does is keep the solenoid engaged in the case of this unit for 3.5 seconds instead of 0.5 seconds. You should not use the 3.5 second engagement - this system is purely mechanical actuation for the passenger door - and, in fact, I would definitely not recommend using it because this heats up the solenoid much more quickly, for obvious reasons. A hot solenoid, even if not damaged, will have less power.

The solenoid was too wide to install horizontally along the lock/door handle connector of the door, which was just as well, because it probably wasn't strong enough to handle this. So, I installed it in a pocket underneath the vacuum switch. A length of rod with a hooked end with a head was provided, one per solenoid, and some screws. The length of rod and the positioning of the solenoid was absolutely critical to success, as well as was the positioning of the hook to the vacuum switch (note the "machine gun" holes I drilled while getting this right). The original spring stamping between the vacuum switch and the latch was no longer used. The solenoid needed to be centered in its operation to "push" and "pull" - it didn't have a lot of travel, and needed all of the distance to build enough of a "whack" to perform the task of moving the valve and the latches. Needless to say, do NOT put the door back together until you verify operation, and putting lithium grease on all moving parts would be a GREAT idea at this point. I guarantee that inexpensive solenoids like these won't move binding, unlubricated parts. If you are having a problem turning your key to lock/unlock the door after the tumbler itself is engaged/disengaged, you will likely have problems with installing this system, or for that matter, any remote system.

I had to bend hooks in the rods and cut them. The rod material is a metal that feels like it can be bent, and maintain its strength, but only ONCE. It was good to have a spare! Note in the photograph that where the original MB parts and the new parts connect or rub, I've covered these areas with shrink tubing as anti-rattle.

Wiring was not fun. The boot between the door and the fender is jammed with wire and vacuum tubing. There was no guideline about the gauge of wire to use but the thicker, the better, to a point - I used very high quality, Teflon-jacketed 16 gauge wire that I picked up from a surplus place. Using thin wire will limit the available current to the already marginal solenoid, making reliable operation impossible. I removed the cardboard from the drivers side kick panel, and, surprise! there was no room to install the "remote brain" there, and there really isn't any good access to feed the wire in or out.

So, I carefully disconnected the boot from the fender, fed wire both to the door and fender, and using the access hole behind the hood latch, used pliers to grab the wire. A Tip - do NOT use your finger - any finger - to do this, unless you have help nearby with some butter or a phone handy to call the fire department. I got my fingers stuck, twice, and it was not fun to get them out. Using Teflon wire made it MUCH easier to feed the wire through the boot. This method was high-risk because it was not very easy to get the boot mounted back onto the door, and there was a real possibility of tearing the now 24+ year old rubber. With that boot loose or torn, water coming in the door and/or fender is pretty much a sure thing, and after that, rust will occur. I don't even want to think about how much it would cost to actually REPLACE that boot. It might be a $5.00 part with 8 hours of labor.

Although I managed to do this and got away with it, I would not reccommend feeding wire this way to anyone. It would be safer to do it the "really hard" way - with a strong solid wire as a "snake" tied to your electrical wire, fed through the door and fender.

I am old school so I used solder and shrink tubing in the wiring, and ran the wiring along the vacuum tubing along the bottom of the door, tie wrapping it where appropriate. I ran the wiring from the door along the bottom of the dash, to the console, where the small "brain" would live. The console wound up to be a very good spot, because the unit fit, and virtually all the wiring you need is in there - fused, full-time power, ground, and connections for the blinkers. This wiring is all part of the emergency flasher switch connector, and I tapped into it. NOTE: DO NOT DO THIS ON AN 86+SL, or any MB with the "convenience" feature. I do not know what this will do to the current sensors that detect "lights out", but wiring this way MAY damage it.

I needed to wire the connector of particular unit in a special way to get reversing of polarity to get the "push-pull" aspect of the solenoid to operate properly. This was diagrammed in the manual fairly well.

So, after getting everything together, I was ready to test the setup. Firstly, the solenoid position took some adjusting, and eventually, I got it to work perfectly, to the limits of the capacity of the vacuum reservoir. I did, however, do something really stupid. Remember, the vacuum reservoir had (ideally) only about five push/pull cycles. So, I had to start the car to replenish the vacuum. Quite a few times. In a closed garage. "But I only started the car for five seconds each time". I got woozy and I had to stop for a few hours. DO NOT OPERATE A CAR ENGINE IN A GARAGE, A CLOSED GARAGE IN PARTICULAR!!!

The blinker flashing feature worked fine. There was even an blue LED to be mounted in the dash to show that the system is engaged. I cut off the blue LED provided and attached it to my red LED that I had previously installed in my heater panel, which, constantly on, had been serving as a $0.25 thief repellant.

Unfortunately, I discovered a fairly serious problem at the dawn of success; the remotes had a range of approximately two feet. This put the limit of the range within the interior of the car, making the installation somewhat useless as a "remote". Past experience had shown that this is the behavior you get when the remote batteries go bad, so after disassembling them, I found the cell type and bought four new ones at Wal-mart for $9.00, At normal retail prices, this was a deal. Still, no luck. So, after contacting the supplier, I had to send the brain and remotes back ($5.00 shipping) and then waited about a week for replacement. However, it was replaced, and worked at pretty good distances thereafter. I should mention that as "cheap" - and I now use the term loosely - as this was, it is a "code-hopping", "learning" type of system so you have to train new remotes to work with the box, which is good. Before this technology, remotes of this type in the 80's and early 90's using dip switches were highly insecure, and a smart high school kid could build a trick remote that could open most garage doors in less than three minutes.

So, there you have it. I no longer have to use the prone-to-wear lock cylinders in the door handles to lock my car, and I have added a useful feature to it that doesn't detract externally visually from originality (like, this matters with my car) - the locks work manually as they always did.

Attached Thumbnails
My ".00" 380SL Keyless Door Lock Installation-detail.jpg   My ".00" 380SL Keyless Door Lock Installation-insideca.jpg  
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  #2  
Old 05-05-2009, 01:39 PM
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Join Date: Nov 2007
Posts: 49
Very interesting and informative post.

I installed aftermarket eBay remote unlock systems in two BMWs and was very happy with the outcome -- but those were electically driven systems vs. the vacuum system that we have in our 107s. As remote locks tend to spoil us, I've often wished for such a system in my SL, but compounding the problem is the fact that I have an as-yet-undiscovered vacuum leak somewhere upstream of my passenger door -- so the 5 or 6 cycles for opening must be accomplished in a matter of a couple hours or the reservoir tank will discharge. Thus, a solenoid/actuator on my driver's door will not open the passenger door after that vacuum "window of opportunity" has expired. But your post has certainly gotten me thinking about it again.

Finally, an old trick with the BMW key remotes (not sure if it will work with normal remotes) is to touch the end of the key to your chin while depressing the remote button. It acts as an antenna and extends the range by about 3X. But there you have metal to chin contact -- not so with the standard type of remote.

Anyway -- Congrats -- really enjoyed your post.

Mike

Last edited by Kimolaoha; 05-05-2009 at 01:48 PM.
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Old 05-12-2009, 09:30 PM
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Join Date: Feb 2008
Location: Fort Lauderdale, Florida
Posts: 439
Wow- what a read- I had a cup of coffee it was that interesting- I do not think that all of that work was worth the cost of the 42.00. Changing spark plugs sounds like more of a fun project. I was thinking of going to a car alarm/remote start/auto door opener- I had it on my 300 SEL and was pleased- especially starting the car while it was 110 degrees outside and letting the AC cool it off. But good job! Whew!

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