Wiring conundrum - brakes, headlights, flashers won't play nice

[Csurge33]

Hello!

I've got a 79 Datsun 620 Manual.  I got this truck to learn to work on vehicles.  I love it, but I'm pretty much green in the troubleshooting department.

 

Recently several problems developed all at the same time.

 

brake lights/tail lights (flashing or not) are very dim 

brake lights/tail lights do not illuminate if headlights are on

signals/hazards will come on but won't flash if headlights are on

signals/hazards will flash but will stop flashing if brakes are depressed (they'll stay illuminated solid)

 

Replaced flashing units for both blinkers and hazards, replaced all bulbs, fuses are good. 

 

I'm guessing it's a ground issue but I can't seem to find it.  Thought maybe it's the hazard switch but it doesn't seem like that should involve the headlights. 

 

Any ideas would be greatly appreciated.  
Thanks for your time!!

 

 

[datzenmike]

Ground maybe.

 

Look behind the pass side rear tail light. There is a round 6 wire connector that joins the chassis harness to the rear tail light harness across the back of the truck. It gets lots of road dirt and water thrown at it by the tires so it's easy for it to corrode the brass connections inside. Unplug and plug together several times to clean them. Wiggle it and see if the lamps get brighter. Have a look into the plug also and if greenish/blue they are corroded. The Black wire is the ground. You could try making a ground connection from this wire to the frame and see if that fixes the problem. Look also to see if anyone has spliced in a plug for a trailer harness.  No one ever does this right and the harness just rots away at the exposed connections.

 

Make sure there is a solid ground wire from the engine block to the body. Everything has to ground and find a path to the negative terminal.

[kelowg]

Ck double filiment bulbs and there sockets. Ck all other connections too. Had rusted running/front signal assemblies on the 521 that caused all kinds of issues like u mention. Also be sure bulbs r in sockets correctly.

[flatcat19]

Their*

[flatcat19]

Check* you* and are* while we're at it.

[Draker]

Clean the fuse box, and clean all your grounds.

[datzenmike]

The 620 fuse box unplugs and two screws and it's out. Scrub clean with soapy water to get all the loose stuff off and any greasy fingerprints and rinse well. Now submerge in a container of full strength lemon juice and salt. You can use a scrub brush or old toothbrush. Then soak overnight.

 

 

In the morning rinse and dry. The citric acid in citrus fruit removes copper oxides (tarnish) and makes it look like a new penny. Vinegar also works but is less acidic that straight lemon.

[EastBay521]

Ck double filiment bulbs and there sockets. Ck all other connections too. Had rusted running/front signal assemblies on the 521 that caused all kinds of issues like u mention. Also be sure bulbs r in sockets correctly.

 

 

Their*

 

 

Check* you* and are* while we're at it.

That's Datslocos for you

[kelowg]

sorry to confuse you. at least you could make sense of it. forgot im not on fb, where no one can spell or write complete sentences

[datzenmike]

f/b..... the downfall of politeness and our society in general.

[Csurge33]

Thank you so much for all of these suggestions!  I'll give them all a shot this weekend and see how it goes.  Thanks again!  Really grateful for your help

[banzai510(hainz)]

unless the wireing is hacked its a corrosion issue. soemtimes changing and moving the fuses and reseating the plug in connection might be all that is needed.

On my 521 its alwasy a dirty fuse box esp with lighting issues. Fuse not seated. or a bad alternator popping the ignition fuse. and or not charging.