Hooligan Posted September 20, 2013 Report Share Posted September 20, 2013 Ok.... just picked up a 1979 620 a couple of days ago. Previous owner said they had lost brake lights one day.... a couple of days later they worked again. I drove it home from Oregon with both brake lights working and both turn signals working. Yesterday I had it on the rack at work and and we noticed the passenger brake light is working, but not the drivers side. Today.... I have running lights, no brake lights, passenger turn signal works, drivers signal does not work. Now.... When you turn on the right turn signal you can hear the flasher click under the dash, no light on the dash, but the turn signal works. When you turn on the left signal you dont hear the flasher, no light on the dash, and no signals work. As for the brakes... if you check power at the brake light switch, the brake light switch is working correctly. I know this is alot... just driving me nuts Quote Link to comment
TheRedWrench Posted September 20, 2013 Report Share Posted September 20, 2013 pull all the fuses and wire brush the hell out of the fuse box (and replace fuses while you're there) that fixed 90% of the problems on my 620 Quote Link to comment
Hooligan Posted September 20, 2013 Author Report Share Posted September 20, 2013 Just replaced every fuse for the hell of it. Checked both sides with a light tester just to make sure everything was good. Still the same problem Quote Link to comment
datzenmike Posted September 20, 2013 Report Share Posted September 20, 2013 Look for the frame harness where it plugs into the tail light harness behind the passenger side tail light. It's a round plug. I find this gets lots of rocks and water spray. Unplug and plug back in several times and make sure that the pins haven't been jammed and pushed out. See it that gets them going. Quote Link to comment
Hooligan Posted September 20, 2013 Author Report Share Posted September 20, 2013 I pulled the plug apart yesterday while trying to find the drivers side brake problem. I also checked the plug with a circuit tester... no light at the plug Quote Link to comment
datzenmike Posted September 20, 2013 Report Share Posted September 20, 2013 Under the pass seat is a 10 pin connector. Retract the seat to get at. This is the cab to frame harness. If everything is good there then the frame harness may be damaged and those wires (copper) will corode to blue powder. I had tail light problems with my 521. Turned out some dick spliced in a trailer plug then cut it off and wrapped it with tape. Water and salt gets in and.... Quote Link to comment
Phixius Posted September 20, 2013 Report Share Posted September 20, 2013 If you havnt found it yet... and if your fuse block looks like this, replace it... this was to get my running lights working when I first got my 521. It also had a corroded wire from fuse block to the connector under the dash. The blue wire is the new replaced one... Ohm the wire harness in sections to help eliminate the good areas... I also had my brake lights not work...in a 521. First checked the brake switch under the dash... jam screw driver in derr... its good...next... I just jumper hard wire to brake light.. tested the harness from firewall back... good...next... so, down to under the dash to the brake switch... there it is... now for those that dont know, to get these buggers out. need to poke somethin in there and hit the little latch that holds it in place... this thing holds it in the plug... Yay, more corroded connections... anyways... When in doubt, Ohm It Out.. HaR Dee har HAR... 1 Quote Link to comment
Hooligan Posted September 20, 2013 Author Report Share Posted September 20, 2013 Luckily the 620 fuse box is under the dash. My 521 was pretty bad and needed a deep cleanin. I'll have to tinker with this some more tomorrow. As of right now I have brake lights and turn signals on the right, and nothing on the left Quote Link to comment
Hooligan Posted September 20, 2013 Author Report Share Posted September 20, 2013 Let me ask this (if it makes any sense)..... if I have read correct, the brake lights run through the turn signal switch. Is there one feed wire from there running to both brake lights? Meaning if I get brake on the right, does that wire also feed the left hand side Quote Link to comment
Phixius Posted September 20, 2013 Report Share Posted September 20, 2013 wiring diagram might help... Quote Link to comment
K_trip Posted September 20, 2013 Report Share Posted September 20, 2013 - removed - Quote Link to comment
Hooligan Posted September 21, 2013 Author Report Share Posted September 21, 2013 I want to thank everyone for the help. After tearing into this.... it still wasnt making any sense. In the end..... the damn main harness connector had a pin come loose and when the two would latch together it would push the loose pin back causing it to lose connection 2 Quote Link to comment
Seeker > 620 KC Posted September 23, 2013 Report Share Posted September 23, 2013 When I got my 79 620 most everything kinda-worked, but poorly and when it wanted. The ghost logic of when and why it worked was crazy like yours. I had already cleaned the battery terminals at the battery as the cables looked good. Next I was working my way thru cleaning all the little individual problem component connections with little success. When I was good and frustrated...I got a "real charge" to find the battery connection at the block was actually tight, but had an oil leak dirty grease build-up over a russsstty connection. The pigtail to body connection was just as crappy. After cleaning just these two points along with the starter connections the majority of of electrical stuff worked like new and the engine ran way better. The real electrical problems were much easier to problem solve after. To me it isn't a process of elimination. I prefer looking at it as establishing a strong power and ground circuit base to begin with before working on the outlaying smaller amp and ohm drawing circuits. Hope this helps? (Now all I have to figure out is why they ran a piece of crappy speaker wire from the fan blower motor under the dash to the passenger side, thru the firewall and to tied it into what looks like the elec choke??? First time I found about it was when I pressed my bare leg up next to the fuse box and it branded my leg it was so hot. So I figure something something in the heating or elec carb circuit is screwy. Quote Link to comment
djpapo Posted April 24, 2014 Report Share Posted April 24, 2014 im having the same problem i can only drive my truck day time cause my tail lights work but no side marks or tail lights at night only brake lights are working day or night ? :crying: Quote Link to comment
banzai510(hainz) Posted April 25, 2014 Report Share Posted April 25, 2014 . djpapo ck fuses and maybe replace them anyways. ck bulbs on side markers. Quote Link to comment
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