Electronics help

[wjjeeper]

Recently picked up a 65 long bed. Experiencing 2 electrical issues and I can't seem to figure them out.

The truck has been mostly rewired but the original fuse panel and gauge wiring are in place.

1st issue - the horn isn't working. I hear a clicking when I try to sound the horn. How can I jumper to test if the horn is any good.

2nd issue - the front signals both work correctly. The rear right works, but when signalling left both rears flash. Possibly related when I push brake pedal the after market tach, oilr press, and temp gauges lights come on.

Ive been going through the wiring diagram and can't figure this out.
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[tincan1966]

1st issue unplug the green wire at the horn itself. Insert a test light probe into connector and ground the test light to the battery or other good ground. Press horn button. Test light should light up. if it doesn't, reconnect the green wire to the horn. momentarily touch your test light to the black wire in the horn relay(just above the voltage regulator location- driver's side of radiator if original) If still nothing. Use a jumper wire to the green wire terminal of the horn. Touch it momentarily, if horn works, it works- replace the relay.

Issue 2 first and foremost, make sure the tail light assemblies are grounded good. Run a ground wire from the light housings to the frame. Also make sure there is a ground wire from the battery to the radiator support and also from the engine to the frame.
Most likely a grounding issue in the rear.

Your accessory and gauge lights are coming on due to a backfeed thru the tail lights since they lack a sufficient ground.

Hint to electrical repair: Only chase one problem at a time. Fix grounds and power supplies first, normally the rest will work itself out.

[wjjeeper]

Test light comes on when I test the green wire. No horn if I jumper from power to horn (green connector). That's what I did before and to me makes sense the horn is no good. Just wanted to ask the pros.

Update on tail lights. I found that the PO ran power for the lights on accessory gauges from the dark green wire at the headlight switch. Disconnected that and brake lights work. But only when headlights off. Signals still work right side only and only when headlights off.
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[tincan1966]

Originally Posted by wjjeeper

Test light comes on when I test the green wire. No horn if I jumper from power to horn (green connector). That's what I did before and to me makes sense the horn is no good. Just wanted to ask the pros.

Update on tail lights. I found that the PO ran power for the lights on accessory gauges from the dark green wire at the headlight switch. Disconnected that and brake lights work. But only when headlights off. Signals still work right side only and only when headlights off.
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It's still a grounding issue in the back. With bad grounding the bulb cannot support both circuits operating at once .
I believe the dk green wire on headlight switch is correct for gauges- it's the one that will dim the stock dash lights. Brown is for the tail lights

[wjjeeper]

I've got a ground from motor to battery and from motor to frame.. I've grounded in the rear from the frame to the box cross member at the very rear.
Asume its good but How would I test this ground is good at the rear lights?

Brake lights function.
Right signal functions with lights off
Left signal make both rear lights flash with lights off.

Pull headlight switch on and rear lights are bright, like they are signalling brake. But I not know.
Right signal doesn't seem to work with lights on.
Left signal does nothing. Flasher doesn't even click.

Front signals work all the time.

That's the recap for tonight.
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[Arekusu]

With wiring, old vehicles and how simple they are... I highly recommend finding a wiring diagram and making sure everything you have "makes sense" before proceeding further forward.. with having parts of your truck rewired by the previous owner(s), you may have tons of "upgrades / reworks " .. And you may or may not want those now or.. they didn't know how to run wires or solder.. so you'll be in for a load of fun. Anyway, there should be a few wiring diagrams to be found using the search (with color) .. I'm off to bed.. been doing wiring for days now. American auto wire.. awesome to work with, and what I've rewired my whole truck with. That's my only plug for them. Good luck.

Alex

[tincan1966]

Originally Posted by wjjeeper

I've got a ground from motor to battery and from motor to frame.. I've grounded in the rear from the frame to the box cross member at the very rear.
Asume its good but How would I test this ground is good at the rear lights?

Brake lights function.
Right signal functions with lights off
Left signal make both rear lights flash with lights off.

Pull headlight switch on and rear lights are bright, like they are signalling brake. But I not know.
Right signal doesn't seem to work with lights on.
Left signal does nothing. Flasher doesn't even click.

Front signals work all the time.

That's the recap for tonight.
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You still need to make sure that the light housings themselves are grounded good. That's the weak link, the grounding of the housing to the sheetmetal.

On the rear wiring harness:
Brown wire = tail lights- should split off into two wires one for each side
Yellow = left brake/turn signal
Green = right brake/turn signal

Easy way to test the harness from the front to back:

Unplug the rear harness connector at the back. Turn tail lights on and probe the connector coming from the front on all wires. ONLY the brown one should light up. Repeat this test for the turn signals, as well making sure the correct circuit is working when it should. Only test one function at a time. if all tests normal, plug the harness back in- if still not working right- then you're problem is from that connector to the lights. Most likely a ground.
That's the easiest test I can give you-should save some time.

I would remove the light housings, and attached a wire to them with a ring terminal and a sheet metal screw, then run that wire along the other harness to under the truck, then secure it where your frame to rear crossill ground is.

[kieth]

To keep from chasing my tail, on a ground problem, we simply soldered a ground wire to each light housing, then grounded this wire to a ground block on the frame at the rear of the truck. Wow lights are bright, not worrying about grounds from the light housing to the body, then the body to the frame. Did the same thing at the front of the truck and life it good.

Kieth

[wjjeeper]

Nearly have this cased!

So I did as tincan suggested and found no power on any of the rear wiring. ...... Interesting.
Started looking around and found that a 1 foot section of the wires were burnt. Apparently when torching out the old springs to install new drop springs the wires got in the way. Haha. There was some serious jumping happening of electrical current.

So after cutting out and replacing that section signals work with lights on. One issue remains. The rear right tail light has both elements illuminated when lights pulled on..?. Indicating brake Any ideas??

Horn now works after replacing the horn unit.

PS : I did run grounds from each tail light bucket to my frame. Thanks for the tip guys.
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[wjjeeper]

Ok guys, thanks. I got this all figured out. Combination of bad ground (which everyone said) and contacts in turn switch were a little off. Replaced the contacts in my repro t/s with contacts from an original.

One thing though I'm hoping someone can explain. My rear, right has a ground from the bucket to the frame, but I need to run a separate ground to the light bulb socket to get rear light and signal to work. It makes no sense to me. The socket is solidly connected to the bucket.????.
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[tincan1966]

Originally Posted by wjjeeper

Ok guys, thanks. I got this all figured out. Combination of bad ground (which everyone said) and contacts in turn switch were a little off. Replaced the contacts in my repro t/s with contacts from an original.

One thing though I'm hoping someone can explain. My rear, right has a ground from the bucket to the frame, but I need to run a separate ground to the light bulb socket to get rear light and signal to work. It makes no sense to me. The socket is solidly connected to the bucket.????.
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Chances are there is some corrosion in the socket/bucket union. They are just a crimp type connection. A lot of guys will remove the bucket, clean it very well and solder the socket to the bucket for a better fit. Also, you may want to inspect the socket to bulb contact area, as well and even tighten the bulb fit a bit by crimping the sides of the socket together SLIGHTLY.
Good luck and glad you got things heading the right direction!