Low Beams Dim...

try replacing the headlamp and see if that fixes it.

If the body ground is getting corroded, it can cause that.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Ben Smith wrote:

The subject vehicle uses a ground-switched headlamp circuit, so there's no "body ground" as such.

DS

The ground-switched headlamp systems favored by Japanese makers for years can develop some truly strange and difficult to trace problems.

Your first step is to measure the segmentary voltage drop to see if you can isolate the portion of the circuit in which the problem is located.

A lot of folks aren't quite sure how to measure voltage drops, so here's a quick refresher. I've written it up in terms of testing headlamps, but the principle is the same regardless of what kind of circuit is under test.

Conditions:

ALL headlamps connected - you may have to backprobe the sockets, but removing the socket from the headlamp invalidates the test.

Circuit to be tested (low or high beam) energized

Connect your voltmeter positive lead to the battery (+) and the voltmeter negative lead to the + terminal of whichever headlamp beam you're testing

-- use the bulb farthest away from the battery. With the lamps on, your voltmeter will give a direct reading of the voltage drop. Write it down.

Then connect the positive voltmeter lead to the ground terminal of the headlamp bulb, and the negative voltmeter lead to the (-) terminal of the battery. With the lamps on, your voltmeter will again give a direct reading of the voltage drop. Write it down.

Add the two voltage drop figures obtained, and this is the total circuit drop.

Remember, light output drops exponentially, not linearly, with voltage drop. Small voltage drops = large light losses.

Maximum acceptable voltage drop is quite small -- once you start seeing drops above 0.2V, start taking note.

When you find a portion of the circuit that contains a large drop, focus in on that portion of the circuit, checking for voltage drop across each junction, connection, and component (switch, relay, etc.).

The terminals on your headlamps are thus:

b -- a| |c

Pinout is:

(a): Common (b): Low feed (c): High feed

With your ground-switched system, (a) is a common FEED (+12V) terminal, and either (b) or (c) will have continuity with battery negative depending on the position of the headlamp switch.

DS

Tried testing direct battery to lamp connection? Maybe charger's the problem.

a voltmeter is your best friend. turn the lights on and check to see if you have 12 volts or better on the positive side of the light. there should be no voltage left on the negative side of the bulb. if there is still voltage after the bulb, you may have a ground issue.

Also, he might want to check both resistances on the bulb's female harness to battery posts. Actually, my best friend is a long piece of wire. I made a direct connection to bulbs. This brightens up the bulbs a bit temporary and isolates the linkage in question at the same time.