JSlaughter

Have a 98 cheroke 4.0 Sport. My headlights were really dim when I bought the jeep so I replaced the wiring harness with a new LMC harness. Everything worked fine until the passenger headlight went out. Wanted HIDs so I got a kit and installed them. Everything good again until the same passenger headlamp goes out.

Here is where im lost. Thinking its the bulb i swap the HID lamps. Passenger side still wont light up. Lamps are good. Bad Ballast? I pull the passenger side out and swap with the drivers side. Same problem. Drivers side lights up but passenger will not. I swapped relays as well. Still not working.

Weird thing is the high beams work on both sides. And ive tested up to the bulb and i am getting power. We also unplugged the new harness and plugged a lamp into the stock headlight socket and it lights up. We refreshed the grounds and tested them as well.

Has anyone run into this before?

BlueRidgeMark

Sounds like it might be the socket, but the other thing to check is grounds.

Bad grounds do weird things.

JSlaughter

Can you have a bad socket and still get 12 volts thru it?

BlueRidgeMark

Yes.


Here's how that works:

Any corrosion in an electrical path forms high resistance. If there is no current flowing in a circuit, you will measure battery voltage anywhere on that circuit, even after a high resistance, like this:


BATTERY+----a----RESISTANCE----b----SOCKET----c

In this circuit, you'll measure 12v at a, b, and c with your multi-meter.

It all looks good, but it's not.

Now look at this:


BATTERY+----a----RESISTANCE----b----SOCKET----c----LIGHT BULB----d----GROUND.

In this circuit, the bulb is lit. (We'll pretend there's a switch in there somewhere.)

In this circuit, the only place we'll measure 12v is at a. We'll have something less at b, and even less at c. We'll have 0 at d.

If that resistance is high enough, you'll measure close to zero at b and c.

But if you check the socket with a multi-meter, you don't have any load on the circuit, so it looks like the first one I drew. You'll see 12v at the socket even if there is some corrosion upstream.

How to tell? Check it with a test light, not just a multi-meter. The test light will put a load on the circuit and show you how it will operate under real conditions. You need BOTH tools in your kit, because each does a different job.


Now, the other thing that could be the problem is the ground for the socket. No ground, no light. You could be getting a perfect connection supplying 12v to the socket, but if the ground is bad, it's not going to light your bulb. Those electrons have to have a way to get back to the battery, and that's through the ground connection. Gotta have a complete circuit.


Make sense?

JSlaughter

Do I test the socket from the new LMC harness or the original stock harness that I plugged the LMC one into?

BlueRidgeMark

Yes.

;-)

JSlaughter

Man this was a joke. FINALLY got both headlights going as it was a bad ballast, but the real kicker is when I plug into the LMC harness only one set of lights work and not the other. So I have the drivers side plugged into the stock harness and the passenger into the LMC. It will have to do!

Bart_3500

If you have all but one or two strands of a wire broken the 12 volts will pass through and activate to the meter but not enough power can go through to make the bulb work.

Hapdad

How many watts are the HID's? If you are powering one off of a stock harness it will only be up to the job for a rather low wattage one.
The stock harness was barely able to run the 55/60 watt sealed beam lamps that came with the jeep it was new. Now it is at least 14+ years old.
Your headlamps were dim for a reason when you started. If you checked the voltage at the connector with a lamp in place you found that you had much less voltage there than what you measure at your battery. This difference between source (the battery) and load (the headlamp) is called voltage drop and is a bad thing.
I looked at the putco harness and another or two, decided that I didnt care for the quality and then built my own. I have full battery voltage at my H4's.
My guess is that harness you purchased is faulty. Build or buy a better just dont risk damaging, melting, ruining, your stock harness if that HID is receiving voltage that is more than 5% or so less than your system voltage. The lost voltage is being turned into heat somewhere and that somewhere may be someplace that you end up wishing it wasnt. Or your Ballast for your HID may end up with a short life.

Hapdad

JSlaughter

Im not sure of the wattage. Ill have to look when I get home. I figured the LMC harness could run them no problem but yes it seems the LMC harness isnt living up to what Id hope it would be. I got a replacement and it was working.... but it is out again. Im not sure if this is just a bad batch of ballasts but im just going with a local company and pay a bit more. Ill just have to go from there.