Both rear license plate lights and trunk light do not go on. The #7 fuse continues to blow (their fuse).

Any suggestions where to go from here.

It is a 1970 914-6.

Haasman

My best guess is that one of the license plate light connections are plugged in backwards creating a dead short.

Remove both license plate lights and unplug them. Then unplug the trunk light and see if it still blows the fuse.

If it doesn't, hook up the trunk light. Make sure you know which one is supposed to be connected to ground. Using a DVOM's continuity function can tell you which one is ground. Then verify the fuse does not blow.

Do the same for the license plates, one at a time. If you look carefully at the license plate lights, you will see one of the connectors is connected directly to the frame of the light. If you hook that one to the power, the fuse will blow because the mounting screw grounds the light to the bumper frame.

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If you still blow the fuse with everything disconnected, you have a bigger problem somewhere in the harness.

Clay

My harness has a cut in it somewhere so no power to either of those lights as well. though about just jumping off the tail light housing to power them but probably try to do an LED.

I agree with Clay. When I re-assembled my car, I incorrectly rewired the trunk light. Kept popping the fuse for the license plate lights. Quick review of the wiring diagram led to the trunk light issue.

Thank you for the replies. I will check it out and report back.

Haasman

Clay- I did as you suggested. I see the logic in those steps.

I found there is no power going to the trunk light, as well as the license plate lights. I did a also see that the connections to the trunk light were reversed, I corrected those.

With 911s when they have a failed headlight switch, the license plate lights do not get power. Is there a similar issue with 914's.

I've dropped the fuse block under the dash. The #7 fuse does get power.

Your additional suggests will be greatly appreciated.

Haasman

I am at work, and doing this from memory, so I could be wrong. IIRC, there is nothing between the fuse #7 on the fuse block and the trunk light except a grey wire.

Drop the fuse block. Take a DVOM and turn on the continuity tester. Check the continuity of the wires between the fuse block and the trunk light. You should have continuity between the side of fuse #7 that has both a grey wire and a blue with a black wire, and the grey wire on the trunk light.

If you don't, you have a break in the harness between the trunk light and the fuse block.


The blue with a black wire on fuse #7 supplies the instrument light dimmer power. The rheostat that works the dimmer is almost always shorted out in some positions. So that is probably the reason the fuse always blows.

Thinking about it, it is possible that some DAPO cut the grey wire somewhere between the fuse block and the trunk light and wired it into the tail light circuit so they would have license plate lights without replacing the instrument dimmer.

Good luck!

Clay

Haasman: I just finished figuring out the exact same problem on my 74. I'm almost embarrassed to admit how many hours I fussed with it. My car arrived without working LP lights, trunk light or back pad light. While I had the interior out I made it my mission to make it right.
What I found was that one of the LP lights had been shorted at the bumper. It's a really tight bend and fit, especially if you use the standard large crimp fittings like my PO's body shop used. Got that fixed but still had a problem. I had continuity from the gray wire at the console to the LP's and trunk light. Wired directly to the battery to the gray wire leading rearward and the lights would work. But no continuity or power from the fuse panel.
Dropped the panel, could not find gray going to #7. Huh. unwrapped the bundle, found gray, but not at the panel. Resigned to just run another gray wire to the panel, but after a good nights rest decided to unwrap the bundle and found a splice about 3 inches from the panel that was non conductive. I guess lots can happen over a 50 year span.
I did a new splice, redid the LP connections with mini connectors, and all is working just fine.
I've attached a couple of photos of the problem spots.Click to view attachment Click to view attachment

Whoops, wrong photosClick to view attachment Click to view attachment

RobK- Thanks I will check the wiring up into the loom

I did follow Clay's suggestion and I do have continuity between the trunk light and #7 fuse.

I will report back.

Haasman

Click to view attachment Click to view attachmentClick to view attachmentClick to view attachment

So If you apply power to the side of the #7 fuse that has continuity to the lights, do the lights work?

It may be as simple as cleaning the contacts on the fuse block and replacing the fuse.

Clay

Minor update- found that one of the gray wires (right side) has failed. I so have continuity from the left LP light connector to the luggage light.

There is also continuity from the #7 fuse post to both above.

I also procured what looks like a good used headlight switch with the rheostat windings look clean and good.

Thanks again for the support. More testing and will update.

Haasman

Check/burnish the grounds under the relay panel

sorry I haven't updated ..... life!

OK so I've verified no power all the way to the headlight switch.

Any suggestions regarding easiest way to get the switch out? I did get the bezel out.

Haasman

Before you do that…

If you’re getting power to the #7 fuse and you have continuity to the light(s):
1) make sure your fuse is carrying the power across the tabs. Put the fuse in and see if you get power on the other side (or check continuity). I’ve seen it where a little corrosion on the tabs blocks the electron flow. Once you have that figured out, you should also have power at + wire for the light(s). Then,
2) make sure the grounds are good and clean.
3) double check that the bulbs are still good, too.

Agree with others that the + wire can easily ground out, esp on the LP lights.

I am not getting power to the #7 fuse.

I did BTW verify continuity from the trunk light to the #7 fuse block position. There is continuity across the fuse, also.

In the wiring diagram it looks like this circuit gets power from the headlight switch?

Should I pulll the headlight switch? I did get the collar off the switch but I don't see how it is maneuvered down under the dash to check?

Sincerely appreciate your expertise here.

Haasman

Ran a separate power to the LP circuit after verifying continuity through the wiring from the fuse holder. All bulbs light up.

There is continuity across the fuse holder and up to terminal on the light switch.

Sounds like a bad light switch. There are two different ones, depending on the year of the car.


Clay

found a good used one. willl replace and report back.

Haasman

..... and no! wtf ....

-I checked continuity from the #7 fuse holder out to the license plate light holders.
-Also checked from license plate light circuit into the light switch. Several connectors have continuity.

Yep, all good EXCEPT it connects to the negative circuit on both license plate lights and the trunk light. Weird.

Not sure what to do next.

Haasman

Does anyone know if there is a separate wiring diagram for 914-6?

There are some connections through a relay that I am unfamiliar with,. Wondering if they enable flashing the fog lights?

Haasman

This is a factory six? If so, there is a different wiring diagram for it.

Clay

Yes it is a factory six. Suggestions on finding a diagram for just the 914-6?

Also in more continuity checking today, I found that from the #7 fuse to the trunk light, both the neg & pos connect.

How would I find that?

Appreciate your help.

Haasman

Here you go.... Sorry they are in black and white.

Click to view attachment


Click to view attachment

Clay

Thank you for the wiring diagram.

Stupid question- since there is continuity from the #7 fuse to both LP lights and trunk light, could I simply by-pass the ground wire going to the trunk light and create a ground right to it at its location?

Haasman

First time replying, long time lurking in the background.
Just had to say THANK YOU all for posting your experiences. I just figured out my trunk light was reverse connected causing the dead short which had eluded my detection for quite some time.
I first noticed that I had no instrument panel lights on my first drive home from buying my 74' 1.8 green beauty. The same night the frunk cable housing let go from its mooring and I could not fill it with over 300 miles to get home. A quarter tank was not going to do it. Shortly after that the fuel pump seals let go nearly draining the tank onto my shop floor! Caught it and got drain pan under it.
Having solved all these issues, I look forward to running about the Black Hills and Big Horn mountains this summer.
Your advisements and topics will surely be needed in the future! Thank you all again!