Jeep Wrangler Forum banner
  • Hey everyone! Enter your ride HERE to be a part of JUNE's Ride of the Month Challenge!

1 - 9 of 9 Posts

·
Registered
Joined
·
45 Posts
Discussion Starter · #1 ·
I just bought an 89 YJ with the 4.2 and the tail lights, marker lights, and park lights do not work. I've checked the fuse, and the fuse block is only supplying 3 volts to the fuse. I have no idea what would cause this or how to get the fuse block off the firewall to check it. Any help would be appreciated.
 

·
Premium Member
'89 YJ 4.2 with MC-2150 Carb & HEI, 2-1/2" Ex. AX-15, NP231 SYE, Adams shafts, F&R ARB, 3
Joined
·
3,909 Posts
Welcome to the forum MadMatt,

At the Bottom of my signature there is a link for Several FSM's (Factory Service Manuals) Open up the one for '89 and go to the lamps section, starting around pg1670 You'll find the Section for park and tail lights, and a diagnostic chart to help you narrow it down easier, if you start at the top and work your way down.

That being said, If you're certain you are only getting 3v at the fuse , Removing and inspecting the fuse block is also in there, but that may open a whole 'nother can of worms.
 

·
Premium Member
'89 YJ 4.2 with MC-2150 Carb & HEI, 2-1/2" Ex. AX-15, NP231 SYE, Adams shafts, F&R ARB, 3
Joined
·
3,909 Posts
Also, We usually Start with ground wires as the culprit for not completing the circuit in a lot of cases involving lighting as most of the lights are grounded to the tub or frame.

Make sure you check the ground wires and clean up the connections from
Battery to Block
Block to Tub
Frame to Tub

I would especially check the one from your Manifold to Firewall, should be just behind the carb and bolted to firewall just to the rear of the valve cover.
 

·
Registered
Joined
·
45 Posts
Discussion Starter · #4 ·
Thank you for the response. I checked the blue wire, which powers the bulbs and got a solid ground there. Also if I take out the light switch and run direct 12v to the wire, the lights illuminate. I just can't figure out how to remove the fuse block to check why it's not getting 12v to that one fuse. Do I need to take the fuse block out from under the dash, or pull the plugs out from the engine compartment side of the firewall?
 

·
Registered
Joined
·
2,297 Posts
I’ve had mine apart a few times I believe there are screws on the engine inside that sandwich the 2 halves to the firewall? Do you have 12 V on the other fuses?


1992, 4.0,5 spd, BDS 4.5 heavy duty lift, jb conversions ss sye, 8.8 with ARB, Aussie front, tj shafts, dual dia.brake booster, 33” bfg a/t
 

·
Registered
Joined
·
45 Posts
Discussion Starter · #6 ·
I do have 12v to the other fuses. I even ran a wire from the ignition fuse to the Tail/Park fuse and got the lights to come on.
 

·
Registered
Joined
·
2,297 Posts
I’m not in front of my jeep and not home but is there a plug type connection in the firewall on the backside of the fuse block or are they wires just running through the firewall I can’t remember? See if you have 12 V to the corresponding fuse socket.


1992, 4.0,5 spd, BDS 4.5 heavy duty lift, jb conversions ss sye, 8.8 with ARB, Aussie front, tj shafts, dual dia.brake booster, 33” bfg a/t
 

·
Super Moderator
Joined
·
12,662 Posts
Find a post by Got it at last. In his signature there's a free link to several Factory Service manuals and a couple Factory Parts Manuals.
Open that link and click on the manual that you need.
There will be a schematic in the electrical troubleshooting section. Find which wire feeds the fuse panel and check it for voltage. It'll be easiest to check the wire for voltage at the firewall connector. Simply ground your digital multimeter and insert the probe into the recess that the wire goes into. You may have to use a needle or pin to make connection to the terminal inside the plug, then, use the probe on your multimeter to touch the pin. If it has 12V, the issue might be in the fuse panel. If it doesn't have 12V, then follow the circuit back to the next point and check it there.

To access the inside of the fuse panel, disconnect the (-) cable from the battery. Look for the firewall plug near the brake booster. There's a bolt in the middle of the plug. Unscrew the bolt until the plug pulls off the firewall connection. I think the bolt has an 8MM head, but I'm not sure.
Then from under the dash, look at the fuse panel. There's two large phillips head screws holding it to the firewall. It's easier to access the screws with tha tach out and using a long phillips head screwdriver.
The fuse panel can be opened up to expose the inner wiring.

Now, with the fuse panel opened up, put a fused jumper between the (-) battery terminal and the (-) battery cable. You want it to be fused in case you inadvertently make a short. Then run a jumper wire between the 12V feed terminal on the under hood connector and the corresponding terminal on the under dash side of the connector.
Then use your digital multimeter to test the voltage to the various terminals that feed the lighting circuit.

Look at the attached pics. It sounds like you have corrosion somewhere within your fuse panel in the circuit to your lights. I had a bad terminal that I replaced, but the way to open the fuse panel is the same.

The above may seem complicated, but once you start, you'll see how it isn't that difficult. What I think you're looking for is a corroded or partial connection that's causing the voltage to drop from 12V to 3V.

Have you turned the knurled knob next to your headlight switch all the way up? I'd do that before digging into the fuse panel. The rheostat shouldn't control the park/tail lights, but it's a quick, simple check and a lot easier than disassembling the fuse panel.

Keep us posted on your progress and don't be shy about asking questions.

Good Luck, L.M.
 

Attachments

·
Registered
Joined
·
45 Posts
Discussion Starter · #9 ·
Thank you so much, that is the exact info I was looking for. I'll give it shot when I get off work.

The knob is all the way up, even though none of the dash lights don't work at all.
 
1 - 9 of 9 Posts
Top