1989 90 lighting wiring troubles

hi all, i have a new-to-me 1989 90 in original unmolested form and am tracking down some faults with the lighting.

headlights, dash lights, and turn signals are all operating as designed.

the tail lamps, front parking lamps (i believe LR calls these "side lamps"), and the number plate lamp, are all non-op.

per the wiring diagram all affected lamps are the only circuits from two dedicated fuses, both of which are not blown. my next step will be to clean up the fusbox and scuff up the glass fuse holders with some emery cloth. in the meantime has anyone else run through this issue and found something different?

i have the factory wiring diagram but it does not show ground distribution which i was hoping to follow.

I suspect it is a switch problem. They are cheap (price and quality) and easy to swap.

Get a meter and test light and start at the fuses.

IME, it is best to buy a bunch of new fuses and change them all. The glass fuses die from vibration and corrosion after 30 years. Make sure you get them out of the UK as the ones in North America are not the right length or type.

javelinadave said:

I suspect it is a switch problem. They are cheap (price and quality) and easy to swap.

Click to expand...

Just one extra point. If it is the switch (which makes sense), make sure you purchase an OEM branded (Lucas) switch. The aftermarket ones are quite poor.

i forgot to mention, i did replace the switch which had no affect. and, the rear fog lamp (which is fed by the light switch on the same circuit) is working so i can rule out the switch, or the wiring from the switch to the fuse panel.

good idea on new fuses, might as well replace while cleaning all the terminals.

Get a meter and trace the fault.

Red90 said:

Get a meter and trace the fault.

Click to expand...

Agreed. Something is disconnected somewhere.

is there a ground distribution diagram for these things or is it just a matter of following wires?

i'll report back after i can spend some time with the meter over the next few days.

acheck said:

is there a ground distribution diagram for these things or is it just a matter of following wires?

i'll report back after i can spend some time with the meter over the next few days.

Click to expand...

Not that I have ever seen. If you suspect it is a bad ground you can unplug each lamp ground and just run a temporary ground from the lamp to the frame.

Sounds like it's time to pull out the side lights and tag lamp and replace with LED ones.
A test light will easily allow you to check current and grounding.

And if you change the engine to a Chevy straight 6, the reduction in vibrations will make the wiring last forever.

Yes you can, Johnny B.
You cold in the upper stretches of the NW?

I bought a completely remanufactured 250 inline 6 today with new Offenhauser 4 barrel intake, cast iron dual stove pipe headers, and all new ancillaries with mounts for $750.
The engine has a high lift cam, but with a mild grind close to stock.
Cast aluminum side covers and valve cover.

There are currently 2 110s here that can be driven.
The 1 with a 292 and the other with a 250.
Mailing list broke 50 today and over half the conversion kits are sold.

Am having trouble getting enough.
Planning the third install this week with this newly remanufactured engine with a 7 year warranty.
Inbox stays flooded with requests...

Congratulations on your 90 purchase.

My money is on fuse box troubles.

Not sure htf or wtf UPS truck engines are in every friggin thread.

LED's wont work either if the fuse conductivity is the issue.

Left side front park lamp, left rear tail light and license plate lamp are fuse 11 on the right bank- 1 up from the bottom. The right side lamps is fuse 12, last fuse on right bank. Kind of hard to believe that all 5 have bad ground. If brake lights are working but tail light isnt (same bulb) then you know its not a ground issue.

Being an 89 will have glass fuses, they just suck.

The lights are all grounded through both the main loom and additionally @ ea corner, front ground to the galv inner fender on ea side, rears ground again on ea side with a sheet metal screw into the tub behind the rear wiring covers in ea corner.

Even if you use qtips and white vinegar to remove any corrosion or just oxidation from the fuse box the damn things will work sporadically. I have found that replacing the fuse into the holder with the circuit on sometime gets one to work when wiggling it around wont.
Hate a damn glass fuse !

I'm certain the busiest man in the Defender community will say installing a 250 or 292 is the answer.

Wait, that already happened !

Nawh, Richard.
I never said installing a 250 or 292 is the answer, even though it is along with LED sidelamps.

Thanks for contributing to the forum. No need for name calling.
How you self identified with the vague indirect comments above, is uncanny.
This is,was, a thread seeking help for an electrical problem.

I would start by checking for power and ground and any of the bulbs. I would probably also verify at more than one since these have so many corrosion issues, you could have more than one problem. I don't know about an '89, but I think NAS trucks have several header junctions behind the dash. Given that the dash vents leak water behind the dash, you probably have corrosion on one of those headers. Do all of the lights even share the same ground?

jymmiejamz said:

I would start by checking for power and ground and any of the bulbs. I would probably also verify at more than one since these have so many corrosion issues, you could have more than one problem. I don't know about an '89, but I think NAS trucks have several header junctions behind the dash. Given that the dash vents leak water behind the dash, you probably have corrosion on one of those headers. Do all of the lights even share the same ground?

Click to expand...

yes

Then after checking the power, install a 292 or 250 to make UD happy..

An update to this. I confirmed both lighting fuses are good and have 12V on both ends of each fuse. From there I went right to each individual lamp and can confirm that problems "seem" to be localized to each lamp, at least in the front. I found corroded bulb sockets etc and could make them work intermittently with random wiggling of fresh bulbs. So, new lamps on order.

Secondarily to that though, the rear lamps seem a bit more f*cked which I think may relate to some trailing wiring, which appears to have been installed by an ape. Will work through that as time allows.

As for the rear, if it is anything like an NAS truck, there are several splices in the right rear a few inches after the harness comes out of the frame.