CJ Headlight Testing ? - *FIXED* - Off-Road Forums & Discussion Groups
Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK

Reply
 
LinkBack Thread Tools Display Modes
post #1 of (permalink) Old 09-12-2003, 04:08 PM Thread Starter
Carpal \'Tunnel
 
knifeboy2's Avatar
 
Join Date: Jul 2002
Location: Macomb, IL
Posts: 2,571
Thanks: 0
Thanked 0 Times in 0 Posts
 
CJ Headlight Testing ? - *FIXED*

Yes my headlights are out again and I'm confused on how to test the wiring. I tested my switch and it tests out ok. I pulled one of the headlights and tested for resistance between the wires. I get a reading when I connect any two of the three connections. Is this a sign that something is shorted out? It appears that I'm getting power to the switch....I believe the power input is the connection all the way to the rear of the switch.

But should I get an ohms reading at the headlight connector like that?

Next on the chopping block is the dimmer switch but I've tested it before and it came out ok.

Any helful hints on the best way to troubleshoot this before tonight/tommorow morning would be fantastic.
knifeboy2 is offline  
Sponsored Links
Advertisement
 
post #2 of (permalink) Old 09-12-2003, 04:22 PM
Old Hand
 
general420's Avatar
 
Join Date: Nov 2002
Location: Nebraska
Posts: 686
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: CJ Headlight Testing ? - Need help before 2pm tomm

Mine did the exact same thing, and it ended up being the dimmer switch. If there is even a question, for $7.00 at the parts store, it's worth it to relace it either way.
general420 is offline  
post #3 of (permalink) Old 09-12-2003, 04:25 PM
Official Curmudgeon
 
CJ7Taz's Avatar
 
Join Date: Nov 2001
Location: Kansas
Posts: 4,705
Thanks: 2
Thanked 5 Times in 5 Posts
 
Re: CJ Headlight Testing ? - Need help before 2pm tomm

</font><blockquote><font class="small">In reply to:</font><hr />
I get a reading when I connect any two of the three connections.

[/ QUOTE ]
That should mean that the headlight you didn't pull is good, you're reading continuity through it. Even if you pull it, you will still read through the high beam indicator bulb in the instrument cluster.

Try the dimmer switch, most common problem.
CJ7Taz is offline  
Sponsored Links
Advertisement
 
post #4 of (permalink) Old 09-12-2003, 04:32 PM
 
Join Date: Aug 2002
Posts: 304
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: CJ Headlight Testing ? - Need help before 2pm tomm

Another thing to look at is the connector on your dimmer switch. I had to put in a toggle switch because the dimmer connector had dry rotted and fell apart.
Is it just the headlights? Do your parking/brake/turn signal lights work?
jlove86CJ is offline  
post #5 of (permalink) Old 09-12-2003, 05:00 PM Thread Starter
Carpal \'Tunnel
 
knifeboy2's Avatar
 
Join Date: Jul 2002
Location: Macomb, IL
Posts: 2,571
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: CJ Headlight Testing ? - Need help before 2pm tomm

Ok, here's what I know as of now.

1. No head lights, no parking lights, no dash lights. Brake lights and turn signals work in front and rear.
2. The headlight switch does work.
3. The dimmer switch works.
4. I have power coming out of the fuse panel.
5. There is power at the switch.
6. An ohm reading with the switch off between the battery and the headlight wires (red to blue) pegs the needle. With the switch on the reading is around 1 ohm (if I'm reading it right).
7. I show around 12 volts going through both switches I have with the switch off ( 1 switch is brand new so I'm sure they're both ok.....I think I'm doing something wrong).
8. With a jumper wire between the + input on the fuse panel and the power input on the switch the lights work.

So I'm really stumped. I have power coming to the switch but its still not working. But when I pull power straight from the battery for the most part they work. Whats going on here?
knifeboy2 is offline  
post #6 of (permalink) Old 09-12-2003, 05:41 PM
Moderator
 
Jim_Lou's Avatar
 
Join Date: Dec 2001
Location: Belleville, Illinois
Posts: 11,485
Thanks: 15
Thanked 22 Times in 17 Posts
         
Re: CJ Headlight Testing ? - Need help before 2pm tomm

When you say that you have power at the switch, is that testing with a voltmeter, with the headlight switch off?

In that situation you could have very high resistance between the fuse box and the switch, and still read battery voltage.

Also, in that situation, if you pull the switch on, your voltage reading will drop way down.

If that's the case, it's a connection from the fuse box to the switch.

The '78 wiring diagram shows that the wire that feeds the switch comes from a splice that also feeds the horn relay, the ignition switch and the brake warning light. If you're having trouble with those too, the problem is from the fuse box to the splice.

If the lights are the only thing screwing up it almost has to be the connector that plugs into the switch. BTW, the splices I looked at were crimped with a sleeve, and looked pretty secure, but I soldered them for good measure.

Also, I had a problem with one of the accessory lines that turned out to be in back of the fuse box. There are regular right-angle female spade connectors on the wires that plug onto male spades on the fuse box. On this particular wire the female connector was loose on the male connector. It would make contact some time, but lose it going over a bump. I just squeezed the connector with pliers until it was a tight fit again.

You could have a similar problem - enough contact area to register on the voltmeter, but not enough to pass the current necessary to light the bulbs.
Jim_Lou is offline  
post #7 of (permalink) Old 09-12-2003, 05:54 PM Thread Starter
Carpal \'Tunnel
 
knifeboy2's Avatar
 
Join Date: Jul 2002
Location: Macomb, IL
Posts: 2,571
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: CJ Headlight Testing ? - Need help before 2pm tomm

Its a new Centech harness so its set up a little different from factory. I didn't know it was possible to show voltage at the switch with no power going. I'll have to tes that. Next step is to see if I get power going through the wire from the fuse panel as it appears the problem has to be there. So frustrating for a new harness.
knifeboy2 is offline  
post #8 of (permalink) Old 09-12-2003, 06:03 PM
Moderator
 
Jim_Lou's Avatar
 
Join Date: Dec 2001
Location: Belleville, Illinois
Posts: 11,485
Thanks: 15
Thanked 22 Times in 17 Posts
         
Re: CJ Headlight Testing ? - Need help before 2pm tomm

If there is no load on a circuit, it doesn't take much of a connection to show full voltage, especially if you're using a new digital meter. It's called "open circuit" voltage, and it's fooled lots of folks.

In plumbing terms it's analogous to a tiny water pipe that's capped off. No matter how small, it will have as much pressure as in the main. But if you remove the cap, you'll only get a little dribble coming out. Reminds me of . . . well, never mind. [img]images/graemlins/frown.gif[/img]
Jim_Lou is offline  
post #9 of (permalink) Old 09-12-2003, 06:17 PM Thread Starter
Carpal \'Tunnel
 
knifeboy2's Avatar
 
Join Date: Jul 2002
Location: Macomb, IL
Posts: 2,571
Thanks: 0
Thanked 0 Times in 0 Posts
 
Re: CJ Headlight Testing ? - Need help before 2pm tomm

Ok, so I used a jumper wire again from the fuse output on the fuse panel to the power input on the switch and everything lights up. So somewhere in between there I've got a problem.

I hooked my meter up to the fuse end of the wire and the input on the switch. It shows around 3.5 ohms (if I'm reading it right.....not so sure I am). Shouldn't the needle peg to the other side of my meter? Any idea about what is stopping the power from going through that wire?

I'm going to call Centech tommorow since they are closed today and hopefully get this figured out.

I am driving my CJ back to school tommorow, 250 miles, in what forecasts show will be rain and thunderstorms. I need these headlights to work properly.
knifeboy2 is offline  
post #10 of (permalink) Old 09-12-2003, 06:49 PM
Moderator
 
Jim_Lou's Avatar
 
Join Date: Dec 2001
Location: Belleville, Illinois
Posts: 11,485
Thanks: 15
Thanked 22 Times in 17 Posts
         
Re: CJ Headlight Testing ? - Need help before 2pm tomm

Well, 3.5 ohms is a lot. It should be only a couple of hundredths. They should have supplied a diagram. See if there is anything in that wire - a switch or a connector - that could have resistance.
Jim_Lou is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Off-Road Forums & Discussion Groups forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome