engine and drivetrain RESOLVED- Starting issues - no seatbelt interlock relay?

[7sis]

My 75 was starting fine one day and then the next stopped to start. When turning the key, the only thing I would hear is one big clicking noise from the engine bay.

-Battery is new and charged. (Still tried to jump start the car)

-Tried to apply 12v to the starter directly which cranked the engine.

I searched the forum and was targeting the interlock relay as the most probable cause.

Looking near the steering column, there seems to be no such relay... Looks like it could have been removed by a previous owner. Although I'm still getting this "fasten seatbelt" light and music show every time I turn the key to Fahrt.

1) Most write ups about this issue are on 74s. Is the location of the relay on 75s the same?

2) Am I Blind?

3) Any other troubleshooting ideas based on the symptoms?

My reference post is the following:

http://www.bmw2002faq.com/index.php?/topic/93425-How-To-Bypass-Seatbelt-Interlock-System-on-1974-BMW-2002A

Here is a picture of under my dash:

Any help would be appreciated.

Edited September 19, 2015 by 7sis

[Mike Self]

If the interlock relay was functioning, you wouldn't hear the clicking.  That sounds like a solenoid that's not getting enough amps, or that isn't working properly.  And we know that's not the case, or hotwiring it would produce the same clicking sound.  

 

Try this:

1.  put a voltmeter on the solenoid wire at the starter, and have someone turn the key to "start" while you observe the meter.  If you get less than close to 12 volts, I'd suspect either the starter switch or the intervening wiring.

 

2.  Put a voltmeter across the thick red wire at the ignition switch (it's hot all the time) and ground.  How many volts there? Then put it to the wire that leads from the switch to the starter (check your wiring diagram for which color wire as it varies between years).  When you turn the key to start, you should again get right at 12 volts.  Much less, and you have a wiring or switch problem.

 

3.  Check the wiring diagram for a '75--I think there's a relay in the starter wiring harness and if so, the relay may be bad.  

 

Let us know whatcha find...

 

mike

[Mike87]

Check your grounds. The big ones in the engine bay. From the battery to the body and from the engine to the body.

[gino2]

F n in ted ry r n xe

[7sis]

If the interlock relay was functioning, you wouldn't hear the clicking. That sounds like a solenoid that's not getting enough amps, or that isn't working properly. And we know that's not the case, or hotwiring it would produce the same clicking sound.

Try this:

1. put a voltmeter on the solenoid wire at the starter, and have someone turn the key to "start" while you observe the meter. If you get less than close to 12 volts, I'd suspect either the starter switch or the intervening wiring.

2. Put a voltmeter across the thick red wire at the ignition switch (it's hot all the time) and ground. How many volts there? Then put it to the wire that leads from the switch to the starter (check your wiring diagram for which color wire as it varies between years). When you turn the key to start, you should again get right at 12 volts. Much less, and you have a wiring or switch problem.

3. Check the wiring diagram for a '75--I think there's a relay in the starter wiring harness and if so, the relay may be bad.

Let us know whatcha find...

mike

1. Unplugged the solenoid wire and checked voltage on the wire when trying to start the car: 11.5V = starting switch is good

I took a closer look to the actual starter:

2 tabs are there (actually 3 but 2 are combined). One tab would be for wire 15 to coil and one to wire 60 to starter switch. I believe the one on the top goes to coil.

Then I identified the potential guys going to coil from loose wires in this area. I believe it is the single black red wire coming from this splice:

Plugged everything... Would still not start. Maybe I need to jump start the car as the battery might now be weaker. This will have to go to the weekend as it is fairly late here.

Check your grounds. The big ones in the engine bay. From the battery to the body and from the engine to the body.

Grounds are in excellent condition (replaced last summer). Edited September 11, 2015 by 7sis

[7sis]

To give an update....

I continued to troubleshoot through the week and looking a starter troubleshooting video on you tube made me think of something I had not done...

One of the first step that I did at the beginning of my troubleshooting steps last week was to check the voltage at the positive terminal of the starter which was 12.4V. This video was proposing to do a voltage drop test while trying to start the car. I did this only to find a whooping 9V drop! I knew that wire was not in the best of the shape but maybe not to that extent...

So I ordered a new oem starter main feed wire (which they had in stock at the Toronto warehouse !!) and voilà! Turned the key, and the car started right away!

Old wire

New wire

Thanks for the support! This was the first of probably many electrical issues on my car... Always happy to learn something new!

Sent from my HTC One using Tapatalk

Edited September 19, 2015 by 7sis