Need help from wiring experts - two circuits not working Options

[jbachert]

1973 1.7

OK - so I will start by saying it's my fault - I accidentally bumped and caused a short at the terminals on the fuse box on circuit 3 (low beams) - so at least we know the cause.

The result is that:

1) The headlights do not work (parking lights, turns, etc do). No low beam, no high beam, no motor up for the headlights. (So technically I guess this is 4 circuits - circuits 1-4).

2) Everything on circuit 8 does not work (fresh air fan, horn, wipers, cigarette lighter).

I know this is going to require tracing out circuits to see where/what isn't working and I just printed out the wiring diagrams and I have a digital multimeter ready to go.

Just hoping for some advice from anybody who has some knowledge of the wiring as to where might be a good place to start, etc.

Thanks,
John

[Cap'n Krusty]

Step ONE. Replace the fuses and CLEAN the contacts in the fuse box. From there, you're on your own.

The Cap'n

[76-914]

Well we need to show a little more support than that (IMG:style_emoticons/default/shades.gif) . Tom or one of the other elec guru's will show up soon but let's start here. Disconnect the ground, drop the fuse panel so you can probe the back side, too. Some are hot and some are switched. 8 is switched IIRC. Battery reconnected; disconnect coil, ign switch on, check both sides of 8 fuse receptor for 12v. Report back.

[jbachert]

76-914 - Thanks for the advice. I think I have it figured out - I worked on it a little after work tonight.

I figured I basically had two problems (circuit 8 and the 4 light circuits) (although I was guessing they were probably related since they both went out at the same time. But, I decided to focus on one at a time to simplify my troubleshooting.

Based on the wiring diagrams I determined that the fresh air relay needed to close in order to send power to circuit 8. I tested the terminals on the fresh air relay socket and the always hot terminal (30) was good. The ground terminal (86) also tested as a good ground. Terminal 86 should go hot when you turn the ignition on - it did not.

I determined from research that terminal 86 is fed from the x terminal on the ignition switch. So, I disassembled the steering column to get to the ignition switch. Terminal X did not go hot when the key is turned on - now we are getting to the problem. So I jumped from the always hot terminal on the ignition switch to terminal X to give it power.

Result - circuit 8 got juice at the fuse box and bang - everything works!! Horn works, headlights turned on, etc! Success! I wasn't able to verify high/low beam or windshield wiper functionality because the wiper/turn signal switch is removed while I have the steering column apart but my guess is they will work once I put it all back together.

I have an ignition switch on order at a local parts store that should arrive tomorrow - I had a gut feeling it was the ignition switch so I called the parts store today from work to have them order one.

Well we need to show a little more support than that (IMG:style_emoticons/default/shades.gif) . Tom or one of the other elec guru's will show up soon but let's start here. Disconnect the ground, drop the fuse panel so you can probe the back side, too. Some are hot and some are switched. 8 is switched IIRC. Battery reconnected; disconnect coil, ign switch on, check both sides of 8 fuse receptor for 12v. Report back.

[Dave_Darling]

Excellent troubleshooting! Glad you found the problem.

Now you're an expert, and you can help the next person out. (IMG:style_emoticons/default/smile.gif)

--DD

[HalfMoon]

1973 1.7

OK - so I will start by saying it's my fault - I accidentally bumped and caused a short at the terminals on the fuse box on circuit 3 (low beams) - so at least we know the cause.

The result is that:

1) The headlights do not work (parking lights, turns, etc do). No low beam, no high beam, no motor up for the headlights. (So technically I guess this is 4 circuits - circuits 1-4).

2) Everything on circuit 8 does not work (fresh air fan, horn, wipers, cigarette lighter).

I know this is going to require tracing out circuits to see where/what isn't working and I just printed out the wiring diagrams and I have a digital multimeter ready to go.

Just hoping for some advice from anybody who has some knowledge of the wiring as to where might be a good place to start, etc.

Thanks,
John

Actually I just recently discovered on my 1973 that they used a horn relay and if it's bad ALL of fuse block#8 will be dead. It's the relay behind the fuse panel closet to the wall (left)

[jbachert]

1973 1.7

OK - so I will start by saying it's my fault - I accidentally bumped and caused a short at the terminals on the fuse box on circuit 3 (low beams) - so at least we know the cause.

The result is that:

1) The headlights do not work (parking lights, turns, etc do). No low beam, no high beam, no motor up for the headlights. (So technically I guess this is 4 circuits - circuits 1-4).

2) Everything on circuit 8 does not work (fresh air fan, horn, wipers, cigarette lighter).

I know this is going to require tracing out circuits to see where/what isn't working and I just printed out the wiring diagrams and I have a digital multimeter ready to go.

Just hoping for some advice from anybody who has some knowledge of the wiring as to where might be a good place to start, etc.

Thanks,
John

Actually I just recently discovered on my 1973 that they used a horn relay and if it's bad ALL of fuse block#8 will be dead. It's the relay behind the fuse panel closet to the wall (left)

I figured out the problem quite some time ago (see my post above) - it wasn't a relay it was a bad ignition switch.