84 Poppin' fuses

[Rockinar]

Bought a 1984 C10. The running lights dont work (bulbs good) and and reading this group found a thread where someone else's didnt either. I checked the T/L CTSV fuse and it was popped. Put a new one in and it quickly popped again.

Someone put a roll pan on it and I only see one ground and it's not even good. The wiring schematics I looked up show the rear lights should have two body grounds, one for each side.


1) Does the T/L CTSV fuse go to the running lights?

2) Bad grounds pop fuses correct? Sorry for the newb question, Im just now having to learn electrical.

[bd]

T/L CTSY = Tail lamps and cab courtesy lamps fuse

Does the fuse pop shortly after installing it w/o you having to switch anything on, or do the tail lamps need to be switched on? 

Although it's possible, generally, poor grounds do not cause fuses to melt.

[peewee0413]

Could be a bad switch or a short somewhere...You need to know when and what blows it. instantly = find the short either the switch or somewhere to the fuse. could even disconnect the switch if it blows instantly to be part of the check to eliminate the switch itself. If fusee holds switch off, then make each part of the switch function. If it blows disconnect that part of circuit and try again with a new fuse. if it doesnt blow then its somewhere that wire fed. Does it happen with high beams on or off... Tons of trials to check the root cause. It's always found with the LASTone, just hope the last one doesn't take long. Isolating electrical can be hard, but break it down into 1 wire at a time...

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[Rockinar]

T/L CTSY = Tail lamps and cab courtesy lamps fuse

Does the fuse pop shortly after installing it w/o you having to switch anything on, or do the tail lamps need to be switched on? 

Although it's possible, generally, poor grounds do not cause fuses to melt.

T/L CTSV fuse pops when I pull the headlight knob to the first position.



New to me truck, so chasing the exterior lights bugs.

- Brake lights work
- Blinkers work front and rear
- Headlights both low/high work
- Interior dome light works

- Neither front or rear running lights work (bulbs are all good)
- Dash lights appear to not be working.

Im trying to chase down why the running lights dont work, and now why the T/L CTSY fuse pops. I suspect its related. Its the headlight switch or a bad ground or something Im thinking.

[peewee0413]

T/L CTSY = Tail lamps and cab courtesy lamps fuse

Does the fuse pop shortly after installing it w/o you having to switch anything on, or do the tail lamps need to be switched on? 

Although it's possible, generally, poor grounds do not cause fuses to melt.

T/L CTSV fuse pops about 3 seconds after I pull the headlight knob.



New to me truck, so chasing the exterior lights bugs.

- Brake lights work
- Blinkers work front and rear
- Headlights both low/high work
- Interior dome light works

- Neither front or rear running lights work (bulbs are all good)
- Dash lights appear to not be working.

Im trying to chase down why the running lights dont work, and now why the T/L CTSY fuse pops. I suspect its related. Its the headlight switch or a bad ground or something Im thinking.

I'm a Electrical Instrumentation and Controls technician by day...Don't look for a bad ground.

look for grounded wire that isn't supposed to be grounded. 3 seconds is just something pulling a little too much and blowing a fuse. Try disconnecting  feed wires for the running lights, which will be on the back of the switch... Brown wire maybe?.. I also think a green wire feeds your instrument panel light. Don't quote my colors, going off memory.

It may be a shorted wire to your running lights. maybe a bad socket, etc. disconnect the two wires mentioned one at a time and hopefully you get lucky. I'd go for the running lights wire first....

 If you own a meter you can find out quickly.

If not you can try every wire on the switch 1 at a time. better have enough fuses lol

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[Rockinar]

I'm a Electrical Instrumentation and Controls technician by day...Don't look for a bad ground.

look for grounded wire that isn't supposed to be grounded. 3 seconds is just something pulling a little too much and blowing a fuse. Try disconnecting  feed wires for the running lights, which will be on the back of the switch... Brown wire maybe?.. I also think a green wire feeds your instrument panel light. Don't quote my colors, going off memory.

It may be a shorted wire to your running lights. maybe a bad socket, etc. disconnect the two wires mentioned one at a time and hopefully you get lucky. I'd go for the running lights wire first....

 If you own a meter you can find out quickly.

If not you can try every wire on the switch 1 at a time. better have enough fuses lol

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I tested it with my last 2 fuses. Both popped almost instant when pulling the headlight knob to the first position.

This video shows the details of the headlight switch, which seems to control the lights Im having issues with. Any chance the headlight switch is the issue?

https://www.youtube.com/watch?v=Tlzdq2nVCcE

[bd]

Pick up a 20-amp, auto reset circuit breaker (image) and fit it with a couple of 18" long, 14-gauge leads with alligator clips.  Substitute the circuit breaker for the T/L CTSY fuse.  If you want to be more sophisticated, connect a 12-volt compact piezo buzzer across the posts of the breaker.  That way the buzzer will sound whenever the breaker pops, making the tool more useful while you're tracing wires.  If the buzzer stops sounding, you've disturbed the harness in proximity to the ground and are close to pinpointing the issue.

Unless the green wire is grounded between the headlamp switch and the 5-amp INST LPS fuse, the issue probably is that the running lamp circuit (park/marker/tail lamps) is grounded.  To determine whether the problem is in the front or rear lamp wiring, separate the rear lamp harness from the front at the firewall bulkhead connector.  The bulkhead connection on the engine compartment side is an assembly of three discrete connectors retained to the bulkhead by a single central screw.  Use a nut driver or 1/4"-drive socket in either 3/8" or 10 mm size (whichever fits correctly) to remove the screw and separate the connector assembly from the bulkhead.  Once the connector assembly is unplugged, separate the 4-wire section from the right side of the connector assembly by sliding it outward.  The four-wire connector feeds power to the rear lamp harness. 

Leaving the four-wire connector disconnected and dangling free, reassemble the bulkhead plug.  Turn the running lamps on (the first detent of the headlamp switch).  If the breaker pops, the issue is in the forward lamp harness or park/turn/marker lamps.  If the breaker does not pop, the issue is in the rear lamp harness or rear lamps.  If you determine that the issue is in the rear section, the first place to inspect is the harness section as it crosses over the rear axle within the left side frame rail in close proximity to the exhaust.  Exhaust heat can melt the wire insulation causing the wires to short together and ground.

Keep us apprised of your progress.

[peewee0413]

I'm a Electrical Instrumentation and Controls technician by day...Don't look for a bad ground.

look for grounded wire that isn't supposed to be grounded. 3 seconds is just something pulling a little too much and blowing a fuse. Try disconnecting  feed wires for the running lights, which will be on the back of the switch... Brown wire maybe?.. I also think a green wire feeds your instrument panel light. Don't quote my colors, going off memory.

It may be a shorted wire to your running lights. maybe a bad socket, etc. disconnect the two wires mentioned one at a time and hopefully you get lucky. I'd go for the running lights wire first....

 If you own a meter you can find out quickly.

If not you can try every wire on the switch 1 at a time. better have enough fuses lol

Sent from my SM-S908U using Tapatalk

I tested it with my last 2 fuses. Both popped almost instant when pulling the headlight knob to the first position.

This video shows the details of the headlight switch, which seems to control the lights Im having issues with. Any chance the headlight switch is the issue?

https://www.youtube.com/watch?v=Tlzdq2nVCcE

I'd take a picture of wire positions, pull all wires but the power wires shown in the picture and see it blows the fuse ...if it does your switch is dead. I assume it's grounded to the metal frame because of the dome light curcuit. If your switch or potentiometer(dimmer) is bad it could be shorted out to ground. If it doesn't blow the fuse when pulling all the wires, add each wire one at a time (switch pushed off will adding the wires) until it pops. then that would be your problem. Also make sure your fuse is the correct size (unlikely the problem). A meter in ohms mode to any connection in the first position to a ground source will tell you the short.

Sent from my SM-S908U using Tapatalk

[peewee0413]

Pick up a 20-amp, auto reset circuit breaker (image) and fit it with a couple of 18" long, 14-gauge leads with alligator clips.  Substitute the circuit breaker for the T/L CTSY fuse.  If you want to be more sophisticated, connect a 12-volt compact piezo buzzer across the posts of the breaker.  That way the buzzer will sound whenever the breaker pops, making the tool more useful while you're tracing wires.  If the buzzer stops sounding, you've disturbed the harness in proximity to the ground and are close to pinpointing the issue.

Unless the green wire is grounded between the headlamp switch and the 5-amp INST LPS fuse, the issue probably is that the running lamp circuit (park/marker/tail lamps) is grounded.  To determine whether the problem is in the front or rear lamp wiring, separate the rear lamp harness from the front at the firewall bulkhead connector.  The bulkhead connection on the engine compartment side is an assembly of three discrete connectors retained to the bulkhead by a single central screw.  Use a nut driver or 1/4"-drive socket in either 3/8" or 10 mm size (whichever fits correctly) to remove the screw and separate the connector assembly from the bulkhead.  Once the connector assembly is unplugged, separate the 4-wire section from the right side of the connector assembly by sliding it outward.  The four-wire connector feeds power to the rear lamp harness. 

Leaving the four-wire connector disconnected and dangling free, reassemble the bulkhead plug.  Turn the running lamps on (the first detent of the headlamp switch).  If the breaker pops, the issue is in the forward lamp harness or park/turn/marker lamps.  If the breaker does not pop, the issue is in the rear lamp harness or rear lamps.  If you determine that the issue is in the rear section, the first place to inspect is the harness section as it crosses over the rear axle within the left side frame rail in close proximity to the exhaust.  Exhaust heat can melt the wire insulation causing the wires to short together and ground.

Keep us apprised of your progress.

I do believe it's likely to be the front or rear lights...

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[Rockinar]

At the bulkhead someone has tapped in the the wires that go to the front of the vehicle to supply for an aftermarket tach. They tapped into the black wire, and the orange wire. This could be one of the reasons. I noticed when I honk the horn, the tach needle pegs out so one of those is for the horn. Im guessing the other is for the running lights which are shorting out when I pull the knob for the running lights because this hackery.

Im out of fuses to test it. Will try again tomorrow or Sunday.

[peewee0413]

At the bulkhead someone has tapped in the the wires that go to the front of the vehicle to supply for an aftermarket tach. They tapped into the black wire, and the orange wire. This could be one of the reasons. I noticed when I honk the horn, the tach needle pegs out so one of those is for the horn. Im guessing the other is for the running lights which are shorting out when I pull the knob for the running lights because this hackery.

Im out of fuses to test it. Will try again tomorrow or Sunday.

SOME PEOPLE'S CHILDREN.  lol..

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[Rockinar]

OK, snipped the wires to the aftermarket tach. We now have running lights.....if the dash dimmer switch is rotated fully clockwise. If I rotate it counterclockwise it pops. Bad switch or hunt for more hackery and taps??

[bd]

Using a tiny thin blade screwdriver or terminal removal tool, depress the tang on the back of the terminal that retains the green wire in the headlamp switch connector and remove the wire.  Recheck for blowing the T/L CTSY fuse (20 amps).  If the symptoms disappear, the green wire that connects the headlamp switch to the 5-amp INST LPS fuse is likely the culprit.  See whether someone hacked into that wire, too, or if the wire is pinched or chafed to ground.  It sounds like the remaining issue is behind the dash.

See images and go to Diagnosing dash instrument lights for additional references.

[Mike81K10]

I hate those wire taps (splices). They are terrible and damaging. Solder wires if needed and replace wires with new terminals is best. Peewee's video said it all I suppose!