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Hello, I Have A 89 F150 With A 300 Straight 6 And 5 Speed That Keeps Blowing The Fuse To The Rear Running Lights And Instrument Lights. Does Anyone Have Any Input On Where To Start To Correct This Problem? I Would Appreciate Any Advice!
you need to isolate where the problem is. One thing is to remove all bulbs on the running lights and if fuse doesn't blow, start replacing one at a time to see if it a light socket.
Ok I removed both the rear running lights. Fuse did not blow! Replaced drivers side and fuse still good. thinking it may be the passenger side but will have to wait and see. Battery went dead on me! Thanks for all the info. I may need some more if this isn't the problem due to battery issues right now.
Ok everything I said in the last post forget about it! I got a new battery and performed the same as above. Well this time I had no running lights in the rear and had instrument dimmer turn all the way down. Checked fuse and it was fine. Turn dimmer up and fuse blew. That was without running lights in place! Any other suggestions or info? Thanks again for all the help.
Trouble seems to follow a defective dash light dimmer rheostat located in the headlight switch. You need to remove the headlight switch and take a look. The wire wound rheostat is probably worn out and broken. I don't know the procedure for removing it on your model truck, but the older ones have a button on the underneath where the wires are connected. when you push the button, the headlight switch will pull all the way out so you can remove the switch. (Edit) What I meant to say was when you pull the **** on the dash the stem will come out and enable you to get the actual switch out.
Last edited by merlynr; Feb 7, 2007 at 07:03 PM.
Reason: more info
1) Cab Marker lamps if you have that option.
2) Front and Rear parking lamp bulbs.
3) License plate lamp/lamps.
It also provides 12 volts to the dimmer switch.
The dimmer switch provides 12 volts or less depending on the dimmer switch position, to Fuse # 17 (5amp) fuse.
That voltage is then applied to the Instrument cluster illumination, Ash tray illumination, Heater/AC illumination, Radio illumination and Windshield Washer illumination control.
Put everythibng back to normal.
Remove fuse #17 (5amp) fuse.
Turn on the parking lamps.
Does the fuse blow?
If it does, the problem is most likely in the wiring for the parking lights and license plate lamp circuit. Look for wiring that has scrapped against the frame rail.
Ok I Checked All Of The Following From Last Two Post And Also Changed The Headlight Switch Just As A Precaution. Fuse #4 Still Blows Once Headlights Are Turned On Even With Dimmer Turned Down. Even Pulled #17 As Stated In Last Post And Still Blows Out. #17 On The Fuse Panel States It Is A 20 Amp Fuse Not A 5. If That Helps Any? Checked Wiring From Rear To Front Doesn't Seem To Have Any Wear Or Exposed Spots To The Frame. Any Other Ideas. I'm Starting To Lose My Mind! Thanks For All Of The Help Guys You Don't Know How Greatly Appreciated It Is!!!!!!!
If you have an ohm meter, disconnect the plug at the headlight switch.
On the plug you'll see a Brown wire. Measure from the Brown wire to ground.
You can use the outer shell of the cigar lighter for ground.
If you measure zero ohms, there is a short on the Brown wire which provides 12 volts for the Parking lamps, Cab marker lamps, licence plate lamp and the Electronic Module that makes the ding ding sound when you leave the headlights on and remove the ignition key.