I might have screwed something up

[wayno]

As the title says, I connected up bosch yellow highbeam headlamps to my 521 KC with a 1982 720 diesel wiring harness, now the drivers side head light/lights are not functioning properly anymore with the stock clear highbeam lamps. Did I melt something in the harness? When in lowbeam mode the drivers side is a bit dimmer than the passinger side, when I swich to highbeams, I basicly lose the drivers side completely, both lamps. If the highbeam lamp is not connected on the drivers side, then the low beam lamp is even dimmer as I thought about just putting the yellow ones in not connected. What did I screw up now?

[izzo]

Are they rated normally? Did the lights do that before or just after you install these lights? Id run a bench test to make sure the lights work correctly. These worked in the 510 before i sold them to you. Check your grounds too. As post below says. I had issues on my 71 wagon ground wire... Jnec has a post about it on here right now too.

[lil89ram50]

switching to the yellows shoulld not have changed anything. i'd check grounds though...

[datzenmike]

You've blown one of the two fuses. Don't trust them on looks alone... replace them. Make sure the contact clips are cleane and making good contact.

[wayno]

The 720 harness is a differant animal than the 521 harness, for one thing the 720 harness is for square headlamps, so round headlamps need the wires in differant plug locations, when I first set the headlamps up they worked correctly with clear round lights over a year ago, I blew a fuse the second the bosch headlamp touched the headlight bucket metal, and it hasn't work right since. The 720 headlight wiring harness is a closed circut, so when that metal housing on the bosch head lamp touched ground, that put a ground in a circut that has no ground, it threw sparks. I changed the relay, no differance, I checked the fuses again, all good, I tried differant headlamps, no differance. I drove it the other night when I fixed the driveline for a ratsun member. I have not put square headlamps in to test it though yet, I was discouraged after a while, was able to get it to work in low beam somewhat, and walked away, but the driverside headlamp is not as bright.

[izzo]

Mine wasn't as bright on my 510, i know its different. turns out it was the ground on the passenger side. But i dont know enough about electrical to give solid advice, besides check yo ground :D

[datzenmike]

Wayno, I have a 720 wiring harness, complete from tail lights to the front including the 720 dash and fuse box in my 620 with round headlights. Yes the middle (top) wire in the headlight plug had to be pushed out and swapped with one of the side ones to make them work. I'm sorry I forget which ones it were but you can get it to convert from rectangle to round headlamps.

[wayno]

OK, the KINGRAT was right, I started to replace the fuses in the area where I found the blown one, I replaced the third and fourth ones from the right with blue 15 amp ones, no differance, then I replaced the one second from the right with a 15 amp fuse and got it all back :D, but that fuse was a red 10 amp fuse. I have been looking all around this place for a fuse cover, I have four 720 wiring harnesses, and not one cover to be found. This is a diesel wiring harness, but I suspect the headlight circuts are the same, what amp fuse goes where? Here is how it is now.

[wayno]

Mine wasn't as bright on my 510, i know its different. turns out it was the ground on the passenger side. But i dont know enough about electrical to give solid advice, besides check yo ground :D

 

 

The 720 headlight circut has no ground between the headlight bulbs and the relay, that's why it is such a pain to wire it to the 521 instrument cluster, as the 521 bright indicator works by grounding it out, but the 720 harness has no ground for the brights indicator, and totally screws up the circut when you try to wire it like the 521. But I fixed that also by using a ungrounded bulb.

[datzenmike]

On the diesel fuse box from L to R

 

blank (exhaust coil on gas motor)

15a Injection pump control unit

15a Rear window defogger

15a Gauge, meter, warning lamp, turn signal, back up lamp,seat belt timer, Detector (diesel)

15a Glow control

15a Wiper, air con.

15a Radio, cigar lighter

15a Clock, inspection lamp

blank

20a Blower motor

10a Horn, chime

15a Stop and hazard lamp

15a Tail/license/clearance/side markers, room illumination

10a LH headlamps, high beam indicator

10a RH headlamps

[datzenmike]

Wayno you have solved a problem I had... I tried everything to get the hi beam indicator to work but failed. Still does not work but I now know why. Tks.

[wayno]

Wayno you have solved a problem I had... I tried everything to get the hi beam indicator to work but failed. Still does not work but I now know why. Tks.

 

 

Chalie69 and I solved the same issue differant, but the same way, by isolating the circut, he did it by cutting the circut in the instrument cluster board, and I did it by buying a plastic 2 wire bulb holder at radioshack, between the two ways mine looks more jury rigged. :lol:

Now to the yellow highbeam bulb issue, the lamp case is made of metal and is part of the ground circut, I suppose I could wrap the lamp in duct tape, but am uneasy about the heat created by the lamp, I suppose I could use these lamps on my 521 work truck if they ground as part of the circut.

Can I buy a totally glass yellow highbeam lamps for my 720 harness?

[banzai510(hainz)]

521s are switchable power if I remember right

I know when I put my H4 harness in it was different to make the lights work. I had to put the jumpers in a connector end tomake it work.

 

I assume the 720 are switchable power but the inner highs should be simple as its only a 2 post system one pwer and one ground. usually its already 50watts wired as most HIGHS

[wayno]

521s are switchable power if I remember right

I know when I put my H4 harness in it was different to make the lights work. I had to put the jumpers in a connector end tomake it work.

 

I assume the 720 are switchable power but the inner highs should be simple as its only a 2 post system one pwer and one ground. usually its already 50watts wired as most HIGHS

 

Yes it is a two post system as long as the lamp is glass, but the 720 harness has no ground after the relay, and one of the yellow bosch lamp wires is connected to the metal housing, so when the headlight lamp metal jacket lets call it, touches the metal headlight bucket, it grounds out and blows the fuses, as there is no traditional ground in the 720 wiring harness headlight circut after the relay.

Saying it another way, each circut in the 720 harness is a little stand alone harness with one positive and one negitive only, if you add a ground somewhere in between the starting and ending points, the circut will not work properly anymore.