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73-87 Chevy _ GMC Trucks => Electrical => Topic started by: bigblockchevelleman on July 16, 2022, 12:17:40 PM
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Subject 1987 chevy truck , NO power to either side of the 5amp fuse , I have no horn just a buzz and the lower interior light when horn is pressed , flashers only light up no flash I've replaced the relay the 5amp fuse ( which was blowed now no power either side of fuse ) any idea or help THANKS so much because I'm totally lost
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You have a short when blowing a fuse like that. Need to inspect your wiring for the system. Use the wiring diagrams provided on this forum. Normally the problem will be where wires have been previously messed with, where they run through a hole or clamp and got chaffed, at a splice, or at a connector (to include bent pins). If the system was previously altered or messed with, that is the first place to look at.
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What is the fusebox cavity label for that 5-amp fuse?
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Thanks , the problem began when I was wiring up the radio and a hot wire touch against the dash and blowed two fuses one was a 20 amp which controlled the gauges ( was replaced which is fine now ) the other was the 5amp so I replaced it and discovered it then had no power at all .I replaced the relay and opened it up and seen where a wire wasn't connected but can't understand why the 5 amp has no power at all THANKS for your help guess I'll go back and check from the radio and see if I can find a broken or burnt wire
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bd it's labeled ACC/LPS Above the fuse and INSTR below it's a 5amp fuse THANKS for the help Steve
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Here's a photo
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The 5-amp "INSTR LPS" fuse is powered through the headlamp switch, thus, becoming 12 volts "hot" only when the running lamps are switched ON.
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Thanks
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Ok thanks went to the shop and with the lights on 5amp fuse has power, traced the stereo wire and didn't find any problems so I have everything working except the horn only get buzzing noise and lower interior light comes on very dim and flashers just stay solid THANKS for the help Steve
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Treat the remaining symptoms as separate problems.
Measure the voltage at the horn when the horn button is depressed. It should measure very close to battery voltage. Does it?
Is it the turn signals or the four-way flashers that aren't flashing? Do the front and rear lamps illuminate correctly even though they don't flash? There are two distinct flashers. Which one did you replace? Try replacing the other one.
Although the cab courtesy light is dim, does it illuminate when it should, when the door(s) open or when the headlamp switch knob is rotated fully CCW?
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Turn signals work along with everything else , only issues I have is no horn and no 4 way flashers I'm going to check steering column wires seeing how the horn and flashers run down column together Thank you for the help Steve
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I stand corrected the dome light comes on if you press the horn 😨I know when I finally find the problem it will most likely be something simple Thanks for the help Steve
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Horn fuse
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Already replaced it's good Thanks for the help Steve
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Update flasher replaced , relay replaced turn singles work in front ( I have the bed off so not sure working in the rear )headlights workbook, markers work everything seems to be working except the horn and the flashers when I turn the flasher on lights stay solidly lit , when horn is pressed interior lights come on I have inspected a lot of wire and haven't found any grounded or broken yet I'll be back at it tomorrow Thanks for the help Steve
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Standard OEM flashers are thermal relays. They require a certain minimum threshold of current flow through them in order to cycle ON-Off-ON-Off-ON-OFF.... Having the rear lamps disconnected (or not grounded as the case may be) might decrease current flow through the flasher sufficiently to keep it from flashing. That's why I typically recommend electronic flashers as service replacements since they cycle based on an internal oscillator that functions independently of the current demand placed on the flasher. Either reconnect the rear lamps and try again or substitute a heavy-duty electronic flasher.
Have you measured the voltage at the horn as I suggested? Isolate the dash wiring from the turn signal switch. Disconnect the turn signal switch from the dash harness by unplugging the wide flat connector alongside the steering column behind and under the dash. Then use a small jumper to momentarily ground the black wire in the dash harness connector. Grounding the black wire should energize the horn relay and blow the horn(s). Does the horn blow normally when doing this?
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When my horn didn't work it turned out to be one of the connectors at the relay plug, it's tang wasn't holding it in place and it slid back so no contact, bent the tang a bit and pushed it back in the plug and all sorted!
Love these no cost fixes!
Graham