no tailights and 10 amp fuse blows

[irishsetter48]

I have an 1989 laredo with a 4.0 engine. I'm having a tough electrical problem. I read through several threads in this forum and did not see where anyone else has had this problem. When I turn my headlights on I blow the 10 amp fuse in the fuse box. The headlights light, but my tail lights do not work and the dashboard lights do not light. How are the headlights connected to the tail lights and dashboard? And why when the fuse blows, do I still get headlights and not tail lights/dashboard? Thanks in advance for your help.

 

[TwistedCU]

check each bulb in the circuit that is dead. One of them may be shorted. Another possibility is moisture/corrosion in the bulb socket causing the same (short) or possibly a ground. If these are all good, you will have to start checking wiring.

 

[jeeperjoe]

ditto, you got a short somewhere in the dash/tail light circuit. my money would go on the corrosion

 

[XJNick]

Hi,

Well for starters the Headlamps, parking/tail lamps, and dash lamps are NOT all on the same circuit.

Instead, the headlamps are on their OWN circuit pulled through a 25 amp circuit breaker which comes from one of the five fuseable links (near the starter relay).

The parking/tail lamps AND dash lamps are on the same circuit and are connected through a 10 or 15 amp fuse in the fuseblock, as you're well aware.

Now, how do they interact with each other? Well, the headlamp switch is actually made up of about 4 switches in one (making it a 4PST switch). It has separate switching contacts internally for: the headlamp circuit, the parking/tail lamp circuit, the dash lamp circuit, and a ceramic variable resistor. So, when you pull the switch to the headlamp position, you are actually switching all these circuits on at the same time, but independantly of each other.

As for what is causing the fuse to blow, that could be one of many things. A good place to start as others mentioned is looking at all the lamps for any that may be shorting out internally or in the socket.

-Nick :!:

 

[irishsetter48]

Thank you to XJNick for the long version. I needed to hear the explanation on how the headlight switch lights 'em all up. I also needed to hear where to check in the taillight. Thankyou to JeeperJoe and TwistedCopper. I'm wokring on it today and should have an answer tonight or tomorrow morning. Thanks again for the quick repsonse.

 

[irishsetter48]

working on it today

Dang! I disconnected the wire harness connector that goes to the passenger's side tail light assembly thinking that I would eliminate all the corrosion issues at once. I did. The fuse blew with nothing connected on the passenger's side. I checked the driver's side...fuse blew. How do I check the wiring as it disappears into the body channel? Another question would be, could it be one of the switches that XJNick talked about? And how do I check those? Thanks again for your help.

 

[XJNick]

Hi,

Here is what I would do to see if it is a problem with the switch or the parking/tail light(s):

Look for a fairly large ( 6 to 8 ) pin block connector either at the front driver's side of the engine compartment (near the air filter) or behind the driver's side headlamp. DISCONNECT this to take ALL of the front lighting off the circuit(s). Turn the headlamp switch ON (note that no front lighting will come on for obvious reasons :wink: ). Does the fuse still blow? If no, the problem is in the front lighting or front lighting wiring. If Yes, try this:

Remove the plastic foot kick-panel on the driver's side of the vehicle under the dash (to the left of the fuse block). Under this kick-panel you will find the horn relay, the illumination relay, and 2 or 3 large connector blocks. One block is solely for Power locks, and windows. if you have no power doors or windows, it will be connected to nothing. One goes to ALL of the rear lighting. The third is for things like the fuel pump, seat belt switch, dome lighting, etc. DISCONNECT the one for the rear lighting (or ALL of them if you're not sure which). Turn on the headlamp switch. Does the fuse still blow? If no, the problem is in the rear lighting OR the wiring which runs from the kick-panel to the rear of the Jeep. If yes, try this:

UNPLUG the illumination relay from its socket behind the driver's side kick-panel. It is a 5-pin relay and should be blue if it is still the original Bosch relay. Turn on the headlamp switch. Does the fuse still blow? If no, the problem is in that relay or the LCD clock OR Radio backlights (if it is a stock radio). If yes,

I'd suspect the headlamp switch is bad, as there is nothing else connected to the parking lamp circuit besides the parking/tail lamps and the clock and radio backlights.

EDIT::: The Trailer harness has a relay which may use that circuit as well. But it is likely NOT an issue.

Good Luck :mrgreen:
-Nick :!:

 

[irishsetter48]

Looking for flares for this......

XJNICK,
Thanks for your help. I went through 15 fuses as I disconnected every harness I could find. The Jeep recently passed Maryland state inspection, which is fairly thorough. I went on the assumption that the tailights passed inspection. After finding a ground wire spliced into the wiring harness for the license plate light ( I didn't do this). I realize the tail lights were not working when it was inspected. I now have all lights working great. Thanks again for your help.

 

[irishsetter48]

XJNICK,
Thanks for your help. I went through 15 fuses as I disconnected every harness I could find. The Jeep recently passed Maryland state inspection, which is fairly thorough. I went on the assumption that the tailights passed inspection. After finding a ground wire spliced into the wiring harness for the license plate light ( I didn't do this). I realize the tail lights were not working when it was inspected. I now have all lights working great. Thanks again for your help.

 

[charlie556781]

Have '87 commache, blown fuse, followed xjnick's advise, turned out to be the switch. ***** to change, gotta be on your head under dash, no slack in wiring to get it out to SEE what your doing. Anyway, thanks Nick. The steps you suggest are simple and efficient..

 

[jimbob2001]

Hi. Everybody! Some. Great. Posts. On. This. Thread - concerning an. ELECTRICAL. Issue. With. This. Jeep. (Blowing. Fuses etc). Some. Things. To. Remember. When. Troubleshooting. Electrical. Issues. That are. Tough Problems: 1. A. DVM. - digital volt. Meter. Can. BE. HANDY. To Work these problems. (Check VOLTAGE. - Check for. Shorts. And. Opens!). This. Can. AIDE. In the. Troubleshooting process. They are. Fairly. Inexpensive. - available. At. Any. Radio Shack. Or. Electronics Parts House. 2. Light. Bulbs. USUALLY. Fail. By. OPENING. UP. - Rare to. See. A. Shorted. Bulb. Filaments. Can be. CHECKED - Visually or with. OHM METER. - Good. Reading. Is. In. The. LOW. OHM. Range. (Less than. 50). Open. Bulbs will. Read. INFINITY or. High OHMS. Sockets. Can. Corrode - Best to. Visualy Insoect and. OHM. Out. Case of bulb socket should be. GND. Center (hot) should go to wiring/fuses/switch assy. Again. DVM. Can. AIDE a great. Deal and cut down Troubleshooting Time, HOPE this. Helps. JB 2001

 

[Jester32]

Just fixed mine for same problem. Of you have trailer wiring inspect very carefully. Mine was shorting to ground taking out tail light circuit. It was corroded in the connector. Factory wiring didn't come on seperate circuit.

 

[Mulecanter]

I had the same problem with my 2004 Liberty, right tail light and instrument cluster out. Turned out to be after market radio install causing it. The orange wire from the Crutchfield wiring kit was not to be used. I didn't however I left it hanging with copper exposed. It must have made contact with the radio housing or other ground source. I called Crutchfield and the guy immediately knew the problem. I went in and sealed the end of the wire and problem solved.