Mercedes-Benz Forum banner

1 - 8 of 8 Posts

·
Registered
1974 450 SL
Joined
·
55 Posts
Discussion Starter #1
I just picked up a sweet 450 SL W107 (California emissions, unfortunatley) and took out the seats, carpet, instrument cluster and center console to clean it up and try to get the air path controls fixed up. I had to unplug the ingnition switch wiring plug for a bit to get at the duct controls. I had to remove the shift lever to get the console out.

After putting everything back together, it wouldn't start. Yes, the battery is charged. The reverse lights come on so I assume the tranmission interlock is OK. I hear the fuel pump come on and a relay somewhere behind the glove box clicks right when the starter should engage. I know about the key switch only turning to start once per full twist. I tried to move the shift lever from park to neutral and other positions but that makes no diff. When the seats were out, the 2 seat-wire plugs (seatbelt and seatpressure) did not keep it from starting two weeks ago. So I don't think they are a factor. It makes no difference with them hooked up or not, so I have them unplugged right now.

I also removed the annoying key-in-the-ignition buzzer/relay by unplugging the 3-wire connector. As I unplugged it, I crossed one of the wires (brief spark) when the pins came out of the connector body so I put it back together, plugged it back in and looked for a better way. The buzzer is now back in operation. On the side of the ignition switch plug there is anothe 2-wire plug that I think opens that buzzer cuircuit, but will disconnecting the 2-wire connector to the buzzer affect anything else?

I jumped power to the solenoid and it starts fine. However, now the alternator idiot-light comes on once it starts running.

There is an interlock issue that I can't figure out. I suppose that when the buzzer wires shorted for a moment, that it took out some fuse or circuitry in the computer (or whatever it is) behind the glove box. All of the fuses in the fuse block panel in the passenger seat-well appear to be in good shape.

Any ideas on how to check out the brain behind the glovebox and why the alternator light came on? It is obviously an interlock issue, but I don't know what else to check...

Thanks,
Scott
 

·
Registered
Joined
·
499 Posts
...Scott ,start from the beginning where you pulled the plug from the igniton switch,have you replaced it in the correct place?.It can only go back in one place ,but if it not in the correct position it will fail to seat completely.
Under the hood,there is a cable running from the positive on the battery to the starter,from the starter is another heavy cable running to a bakelite block with three terminals,one large,one medium and one smaller size.
Put the trans lever in nuetral,pull the handbrake on,
Turn on the igniton.
run a wire from the positive on the battery to the middle terminal on that block,the starter should turn the engine over and start it.
If not ,touch the smaller terminal,in either case the starter should work.That will eliniate any problems with the starter or it's solenoid.that only leaves the trans nuetral switch or those lock out devices you spoke of.
 

·
Registered
1974 450 SL
Joined
·
55 Posts
Discussion Starter #3
Thanks. Yes, I checked the seating of the ignition switch lume plug a number of times. I even tried jiggling it while I tried turning the key. Then after pulling the buzzer relay and having the three pins pull out of the connector body, I though better and put them back. First, I checked the two that made the buzzer sound and then put the third wire on the only pin left. So that should be back the way it began. The trans lockout wiring looked clean and so I did not disturb it. It's also a real pain to get to other than to look at it. So perhaps I am back to the seat lockouts? I see one of the car side plugs has 12v on it. The seatbelt buckle circuit is closed and opens when the buckle is inserted (or did I recall that backwards...) The seat pressure switch closes when weight is put on the seat. So it seems simple to bypass these 4 plugs and be done with it, right??? Can I assume that shorting the seat pressure car-side plug and just leaving the seatbelt car-side plug unplugged should do it? Or does the seatbelt plug have to be closed initially and then opened to enable starting.

I just can't follow the German logic [xx(]
Do you have the wiring diagram for this nasty circuit?

Scott
 

·
Registered
'80 450SLC Afro RHD Ikonengold
Joined
·
2,956 Posts
Your computer box is more like fuel mixture regulator than a "computer". If you can somehow start the engine and it runs smoothly than it means it is fine. I belive the "idiot" light is directing you toward the culprit.
Anyhow, send me your email to [email protected] and i will forward the copy of electric diagram to you (cca 1.5Mb in two .pdf files)
 

·
Registered
1974 450 SL
Joined
·
55 Posts
Discussion Starter #7
Thanks for the diagrams. Although I have yet to jump back in to the troubleshooting, I know that they will be a great help.

Thanks again,
S
 
1 - 8 of 8 Posts
Top