Looking at the diagrams that I have and with a fair understanding of auto wiring I was thinking that the door lamb switches and the parking brake switch leads were remote grounds to their respective lights. And that the switches would be NO and close when the pressure was off.
Both circuits seem like they might have passed through the seatbelt box at some point, it is long disconnected.
Both of my door switches are worn to the point of not working. The parklng brake light worked before I dug in.
Am I missing something other than a few marbles?

Looking at 73 schematic, you have summed it up.

Get troubleshooting.

It's a 74, It would help to know where the door jamb switches go to ground if anyone knows. I also have a double gray that feeds the plate and trunk lights and it's dead in the console. I just had the fuse panel down and did not see anything hanging.

Not sure about the ground location, but when you say "dead in the console" for the trunk/LP lights, where are you measuring?

There's a dedicated fuse (#7) on my '73 that the gray wire goes to. On the other side of that fuse, another gray wire goes to the light switch to get power when the lights are on. If the fuse is good and there is no voltage on either end when the lights are on, I'd trace it back to the light switch.

Ron

I have two 1974s and have had to get the door switches working on both of them (fuse #11), complicated by the circuit going through the smaller relay/buzzer the and next to the larger seat belt safety interlock relay under the passenger seat. Those relays ground to the floor plan just behind the right side screw holding the black mounting block for both relays. I've disabled the seat belt interlock in the usual way but the relays remain in place and need that ground screw.

thanks guys, I was thinking that the relays were still a part of these circuits even being bypassed. Going to drop the fuse panel again and keep poking around. The headlight switch seems to be OK, just no power to the gray lead. Maybe I knocked it off putting the panel back in. I need to step away from the car for a bit, need to let my neck and knees get back to normal. I don't fit too well in the footwell, and it's time to get get the boat ready for spring

I'm lost. OP started related to door switches (which control the interior light) and parking brake switch and parking brake light that went in-operative. All are driven by ground switching.

Then middle posts changed to console / trunk lights and grey wires and chasing around power feeds? where did that come from ?

Which problem is being worked on?

The Prospero's garage schematic is worthless to understand what was going on in the buzzer/relay and seat belt interlock system. Use the Haynes Manual. The seat belt interlock/buzzer/warning lamp and door switches are totally independent circuits from the park brake light.

Interior light and park brake warning light are independent of the seat belt warning buzzer and lamp presence. Yes, buzzer does get ground feeds from door switch contact and column key switch but interior light and park brake lamp light operation are not affected by the buzzer/seat belt warning lamp.

I'm happy to help but need to know what problem is trying to be solved. Need to focus on one thing at a time and using schematics and DMM.
@robkammer

Did you read the OP's 2nd post?

Yup. Has nothing to do with OP.

The door switches on later cars ground thru the switch housing and the hold down screw same as the switch for the hand brake light.



The double grey is for center console lighting and continues back for the trunk and plate lights. Power comes off the headlight switch terminal K and goes thru fuse 7. Current tracks 33, 59 and 60 on the diagram.

Thanks Superhawk: I do jump around, sometimes forgot I posted something too. Sorry. This project started out as fuel lines and the project creep took me to carpet, and that took me to the center console and fusebox wiring. Before putting it back together I want to be sure everything works as it should. Prior to disassembly the gauge lights did not work, nor did the interior/trunk or plate lights.

At this point here is what I have: Continuity from the gray in the console back to the plate lights. Continuity from both door switches to the cabin for the backrest light. If these switch through the switch to ground I assume I also need to send a direct ground to the light in addition to the brown/white.

I have gauge light power now for the console harness and it's cleaned and ready.

The seatbelt relay has quite a few wires just laying under the seat. Between the Haynes diagram and drawings in the notebook site I have that pretty much back together but I don;t think its right yet.
Using the attached drawing I have a couple oddities. Where the drawing calls for a green/white (#10) there was a double yellow/white attached and I do have a loose green white. The drawing makes no reference to a double yellow/white and also shows nothing connected to terminal 11. In addition to the double yellow/white I have a single yellow/white connected to #9 per the drawing.

I've also referenced Jeff's photo also attached, I have the three black leads connected to the relay like the picture but they lead nowhere.

Another issue if I ground the parking brake switch lead the red flasher light flashes but nothing else.

So, in addition to the relay board issue I have to provide power to the gray lead that heads to the rear, figure our the parking brake issue, and confirm that I need a hard ground to the backpad light.

Tonight I was going to take the relays home and diagram the terminal numbers to compare with the Haynes schematic but I you have any ideas please share.

Once I get this straight, and before the interior goes back in I'm going to replace the fuse panel. Then if anything is wrong at least I'll know who did it!

I once bought a really nice classic Boston Whaler. Did not realize until I went to put a battery disconnect switch in that the PO had rewired EVERYTHING with brown lamp cord. That was pretty bad but this little teener is proving to be quite a head scratcher.Click to view attachment Click to view attachment

Thanks Superhawk: I do jump around, sometimes forgot I posted something too. Sorry. This project started out as fuel lines and the project creep took me to carpet, and that took me to the center console and fusebox wiring. Before putting it back together I want to be sure everything works as it should. Prior to disassembly the gauge lights did not work, nor did the interior/trunk or plate lights.

At this point here is what I have: Continuity from the gray in the console back to the plate lights.

This is a different issue than the door switches. You need the Haynes Manual. IIRC these are switched to the light siwtch and I am not sure about the ground for these but somewhere on the body. Same for the trunck switch.


Continuity from both door switches to the cabin for the backrest light.

I'm very familiar with this circuit in the 73 as it is a series of switched grounds that are daisy chained. The 73 I've done but the 74 wiring is different so you need to be very sure of which year they are. Make sure your door switches are not worn out....very sure check them also for continuity as they wear out. If you have the four wire switches in the car they are SOL and you'll need to source used that do work. Again I think the 74's are a mixed bag but check what you have in your car to the Haynes Manual.

If these switch through the switch to ground I assume I also need to send a direct ground to the light in addition to the brown/white.

If you are discussing the backpad light then yes but the switched ground wire should be there already...it's a conjoined pair of grounds (one for each door switch. Sounds like its not there. You should ring the correct one with your DMM to the wire in the door. So not sure what you are saying here. To trace wiring....do one at a time...don't go ADD and start jumping around.


I have gauge light power now for the console harness and it's cleaned and ready.

Comes off the light switch power and IIRC there is a grounding wire on the back.

The seatbelt relay has quite a few wires just laying under the seat. Between the Haynes diagram and drawings in the notebook site I have that pretty much back together but I don;t think its right yet.
Using the attached drawing I have a couple oddities. Where the drawing calls for a green/white (#10) there was a double yellow/white attached and I do have a loose green white. The drawing makes no reference to a double yellow/white and also shows nothing connected to terminal 11. In addition to the double yellow/white I have a single yellow/white connected to #9 per the drawing.

Sorry can't help here I had a 73 so....sure somebody else can help there.

I've also referenced Jeff's photo also attached, I have the three black leads connected to the relay like the picture but they lead nowhere.

Another issue if I ground the parking brake switch lead the red flasher light flashes but nothing else.

So, in addition to the relay board issue I have to provide power to the gray lead that heads to the rear, figure our the parking brake issue, and confirm that I need a hard ground to the backpad light.

I'd do one circuit at a time.....just some advice.

Tonight I was going to take the relays home and diagram the terminal numbers to compare with the Haynes schematic but I you have any ideas please share.

I'd lay that Haynes wiring diagram over my bed and stare at it until it looks familiar to you....maybe with a beer or two.

Once I get this straight, and before the interior goes back in I'm going to replace the fuse panel. Then if anything is wrong at least I'll know who did it!

I once bought a really nice classic Boston Whaler. Did not realize until I went to put a battery disconnect switch in that the PO had rewired EVERYTHING with brown lamp cord. That was pretty bad but this little teener is proving to be quite a head scratcher

The German engineerrs did some clever wiring tricks and possible the PO did some nipping with a side cutters...Good luck.

Hey guys: Sorry I been away for a while. Not all of it was staring at the diagrams and the wiring, but I did spend too much time on it. Yesterday I FINALLY found what was making me crazy. I needed to unwrap the bundle at the fuse panel and across the left side foot well to find the gray wire that I could not locate that powers the rear plate lights.
found it stuck to #6 fuse rather that #7. It had been crimp spliced to a black wire at some point.
The splice had no continuity so I pulled the casing off. It had a crimped metal splice band that must have corroded and was not allowing any current through. Would not have believed it without a meter to check.
Pulled it apart, soldered and sealed a new end and I'm in business. All systems are working so now I can replace the fuse panel and know that if something doesn't work it's because I screwed up!
And if my carpet ever gets here I'l be able to put it all back together again.Click to view attachment Click to view attachment