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73-87 Chevy _ GMC Trucks => Electrical => Topic started by: impco lpg on September 10, 2017, 10:03:58 AM
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hi all,
I have replaced all my lights units to LED (NOT THE BULBS) front and rear. when i just turn on my indicators or hazards, the front and rear side lights flash at the same time. but not at full power (side lights only), is this an earth fault or do I need a resistor flasher unit. FRONT MARKERS ARE BULBS.
any help would be appreciated THANKS
1985 chevy c10 stepside 5.7 2wd
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The front side markers are supposed to flash with the turn signals, but they should flash at normal brightness, not dimly. To restore proper function read on.
The factory front side markers are wired BETWEEN the forward turn light filament and forward park light filament power feeds. The side markers do not use a conventional ground, but instead ground THROUGH the front turn or park filaments that aren't powered at the time. The factory configuration works, because the side marker bulbs (194) require only a fraction of the current necessary to illuminate the park and turn filaments of the forward turn/park lamp bulbs (1157). Essentially, you've introduced high resistance grounds for the side marker lamps by substituting the LED lamps for conventional filament bulbs. The side marker filaments require more current to illuminate than will pass through the LED lamps to ground.
Installing a 10 Ω, 25 watt to 20 Ω, 15 watt resistor on both sides of each side marker lamp to ground should solve the problem - something along the line of these (http://www.ebay.com/itm/1Pcs-50W-20-Ohm-Gold-Tone-Aluminum-Housed-Wirewound-Power-Resistor-Tolerance-5/371645846729?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D2%26asc%3D46088%26meid%3D092a3a0f7e214af5a6cf5ae76c083ddb%26pid%3D100005%26rk%3D2%26rkt%3D6%26sd%3D301110462829&_trksid=p2047675.c100005.m1851). Using resistors with greater wattage ratings (up to ~50 watts) won’t detract from the resistors’ function, BUT avoid using resistors with lower wattage ratings than specified above or they will overheat. You will need four resistors to complete the task.
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thanks for your reply.
as I live in the uk the previous owner has altered the front wiring. so that you do not have amber front markers, they only come on when you indicate pic two. there was a white front bulb 194 in the top headlight. so am I right in thinking I need to revert back to standard as factory first ?
I have some pics. is this standard wiring colours and connectors to a 1985 c10 ? (there is one at each side)
the last pic shows two black wires that come from the side marker (drivers side) ln to light blue and green not as factory I think ?
the first pic shows a junction box on drivers side inner fender, there are two light green wires that have been cut that go into a relay.
HELP :(
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Reverting to the factory wiring would be a solid move. Neither the white junction box nor any of the white connectors are original to a U.S. built truck. As to the wire colors, GM uses those colors in the forward lamp wiring, but since it isn't original I cannot speak to whether the colors tie directly to the original color scheme. Refer to the 1985 Wiring Manual (http://www.73-87chevytrucks.com/techinfo/7387CKMans//Wiring/ST_352_85_1985_Chevrolet_GMC_Light_Truc_Wiring_Manual_CK_10_30_Only.pdf) to help sort it out.
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ok I let you know how I get on cheers neil
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update, I have reverted back to factory at the front wire loom. everything is working as it should (front markers and side markers amber) and both indicate as they should. the relay with the two green wires that were cut turned out to be for the high beam. the back lights work fine indicating left or right only, BUT when I put the hazards on the red tail lights still flash with the indicators, I have a video of the problem. is this still a ground fault ? or do I still need a resistor/s ?
YouTube video link
https://www.youtube.com/watch?v=8_4omd6rkZk
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Your custom installation needs clarification. Are the inboard pencil lamps you installed upper half amber, lower half red? How many wires connect to the inboard pencil lamps and how are they wired with regard to brake/turn/tail/backup? How about the outboard pencil lamps - what is their color and function and how are they wired with regard to brake/turn/tail/backup? In other words, what are you trying to accomplish with the various lamps and exactly how did you wire them? Since it is a custom installation, you need to be explicit.
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the rear pencil lights are upper amber and lower red. (uk spec)
there are 4 wires per pencil light lh/rh. the RED is for brake and tail ONLY as per (pic 1), the amber is for turn right/left and hazard ONLY.
the backup is the outer x6 led light.
all the rear lights wires are in a 10 way junction box at rear of pickup (pic 2) the wires to the right of box come from the white junction
box (front fender) there are 7 wires. blu is tail, red is indicator lh, yel is side lights, wht is earth, brn is stop, blk is indicator rh, grn is backup. there are two bulk head connectors (pic 3) as per factory ? right is rear lights left is front lights ? there are 4 wires coming from the right connector dk grn, lt grn, brn, yel. which go into white connector (pic 4) they connect to the rear loom. dk grn = blk, lt grn =yel and grn, brn =blu, yel =red
pencil light wire colours
red is stop
wht is earth
brn is tail
yel is indicator lh/rh
this sounds a little confusing but there is something not right, any help would be most appreciated regards neil
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update, I have reverted back to factory at the front wire loom. everything is working as it should (front markers and side markers amber) and both indicate as they should. the relay with the two green wires that were cut turned out to be for the high beam. the back lights work fine indicating left or right only, BUT when I put the hazards on the red tail lights still flash with the indicators. I have a video of the problem. is this still a ground fault ? or do I still need a resistor/s ?
YouTube video link:
https://www.youtube.com/watch?v=8_4omd6rkZk
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the rear pencil lights are upper amber and lower red. (uk spec)
there are 4 wires per pencil light lh/rh. the RED is for brake and tail ONLY as per (pic 1), the amber is for turn right/left and hazard ONLY.
the backup is the outer x6 led light.
all the rear lights wires are in a 10 way junction box at rear of pickup (pic 2) the wires to the right of box come from the white junction
box (front fender) there are 7 wires: blu is tail, red is indicator lh, yel is side lights, wht is earth, brn is stop, blk is indicator rh, grn is backup. there are two bulk head connectors (pic 3) as per factory ? right is rear lights left is front lights ? there are 4 wires coming from the right connector dk grn, lt grn, brn, yel. which go into white connector (pic 4) they connect to the rear loom. dk grn = blk, lt grn =yel and grn, brn =blu, yel =red
pencil light wire colours
red is stop
wht is earth
brn is tail
yel is indicator lh/rh
(http://forum.73-87chevytrucks.com/smforum/index.php?action=dlattach;topic=35608.0;attach=37563;image)
Review the wiring connections to the inboard two-color lamps...
- Stop - brown (front) > red (both rear)
- Tail - blue (front) > brown (both rear)
- Left Turn - red (front) > yellow (left rear)
- Right Turn - black (front) > yellow (right rear)
- Earth (Ground) - white (front) > white (both rear)
...then refer to the above image.
The white (earth) wires from the LED lamps do not connect to the white (earth) wires from the front harness. Unless there is a viable shunt between the "earth" bus and the LED 'earth' strip, the LED lamps are not properly grounded. Otherwise, run a temporary jumper wire between the LED 'earth' strip and shiny, bare metal on the right frame rail to see if there is any improvement.
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If the problem persists after the ground for the rear lamps has been verified, temporarily disconnect the front side markers (remove the bulbs) and recheck the rear lamps for symptoms.
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there is a jumper earth wire fitted (black loop wire left side of box) and I have tried a separate earth just for the rear lamps (still fault)
when I removed the front marker bulbs (194) and (1157) both sides the rear lights work FINE AS THEY SHOULD NO RED FLASHING :)
so do the front markers need resisters ? I have x4 50watt
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So, you're back to running incandescent bulbs up front instead of the LED lamps? Recheck the grounds to the front park/turn lamps. Reinstall the front 1157 and 194 bulbs. Connect a voltmeter negative probe directly to the battery negative post. Select the voltmeter DC 10 volts scale. Connect the voltmeter positive probe to the left turn lamp ground wire. Energize the left turn signal. Measure and record the voltage drop. Repeat the process with the voltmeter positive probe connected to the right front turn lamp ground wire. Post the results.
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battery side: energize right turn .25 volt
energize left turn .15 volt
NOT SURE IF IM DOING IT RIGHT :-[
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(http://forum.73-87chevytrucks.com/smforum/index.php?action=dlattach;topic=35608.0;attach=37572;image)
Measure similarly on both sides. This measurement checks the integrity of the ground return path to battery.
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the description and the diagram I get, ITS THE MULTIMETER I HAVE NO EXPERIENCE WITH
I have a pic of the multimeter I have is it set right ?
sorry to sound dumb
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It appears to be set correctly to DC volts and has auto-ranged to the millivolt scale.
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battery side. right turn : high reading 168.4 low reading 148.1
left turn : high reading 94.0 low reading 83.7
with hazards on. right side : high reading 189.2 low reading 150.2
left side : high reading 105.7 low reading 83.7
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battery side. right turn : high reading 168.4 low reading 148.1
left turn : high reading 94.0 low reading 83.7
with hazards on. right side : high reading 189.2 low reading 150.2
left side : high reading 105.7 low reading 83.7
Respectfully, the posted numbers are meaningless without the units of measure. Are the readings in mV? What is "battery side?"
The threshold voltage (minimum voltage drop (V0) needed to force current flow through, hence luminescence from, an LED) for red LEDs lies within the range: 1.6 - 2.1 volts. You need to clarify your responses.
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all the readings given are in millivolts.
battery side, is location of battery (passenger side fender)
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I've been trying to wrap my arms around your description of the symptoms to determine what the exact cause and solution are. Your measurements indicate there are less than perfect grounds in the forward turn/park lamps. The manner in which the LED tail lamps tie into the front park lamps results in a voltage divider configuration whenever the turn/hazard lamps are energized. Under these specific circumstances the resultant voltage applied across the tail lamp LEDs (~4 volts net across the LEDs with current limiting resistors) barely surpasses the LEDs' threshold and illuminates them. I think the voltage divider configuration is the cause of the symptoms, exacerbated by the less than perfect grounds for the forward lamps.
Assuming you've described all of the symptoms (haven't left any details out), a 1N5402 3-amp diode installed in the brown "park lamp" feed wire, between the forward lamps splice and the bulkhead connector with its cathode band orientated toward the forward lamps, should isolate the LED lamps and prevent cross-feed. A possible complication might be introduced by the physical placement of the rear lamp harness tie-in to the lighting circuits in the engine compartment. The diode needs to be located between the tie-in of the rear lamps and the splice to the forward lamps.
(http://forum.73-87chevytrucks.com/smforum/index.php?action=dlattach;topic=35608.0;attach=37642;image)
Edit: added quantitative information
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And, correct the grounds to the forward lamps.
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i have ordered these
http://www.ebay.co.uk/itm/10-x-1N5402-Rectifier-Diode-3A-200V/253036700226?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649
regarding the forward turn/park lamps GROUNDS, am I looking for the volt meter readings to be equal/similar to each side LH/RH.
not one side higher than the other ?
the only other thing I have not mentioned is, there is an alarm system fitted. that does the door locks/windows and ignition cut off. when the alarm goes off, as well as a siren tone it FLASHES the side lights. and when a door is opened. (using the door switch) could this be a problem ? alarm wire diagram pic below
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regarding the forward turn/park lamps GROUNDS, am I looking for the volt meter readings to be equal/similar to each side LH/RH.
not one side higher than the other ?
The measured voltage drop across the ground paths to the battery negative post should be as close to zero as you can get it. This is true for all low- to medium-current grounds (<25 amps). Be sure to perform a thorough inspection of the wire condition and wire-to-terminal connections. Oxidized or frayed wiring should be cut back, cleaned, re-terminated and soldered using 60 Sb/40 Pb or 70 Sb/30 Pb rosin core solder - or entirely replaced, terminated and soldered.
Take an inventory of the vehicle grounds and service them all (thoroughly burnish them then coat liberally with water rejecting antioxidant paste). You should find the following vehicle grounds (recommended wire size is included for any ground paths that need to re replaced or fabricated anew):
- battery to engine (2 gauge)
- battery to right (passenger) frame rail (10 gauge)
- battery to radiator support (10 gauge)
- back of right cylinder head to cabin firewall (5/16" braided strap or 10 gauge)
- dash lighting and interior appliances to cabin left kick panel sheetmetal (various 18 to 16 gauge)
- rear lamps to bed (18 gauge)
- bed to right frame rail (14 gauge)
- cabin firewall to engine compartment hood (bonnet) (1/4" braided strap (preferred) or 12 gauge, suitably placed and long to allow opening and closing of the hood without catching, excessive flexing or stretching of the wire)
Additional primary ground connections are okay. If any of the recommended ground connections are missing, fabricate and install them!
I doubt that your alarm is an issue.
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just an update I only have 3 of the 8 earth/grounds you have listed :(
NO battery to right(passenger) frame rail
back right cylinder head to cabin firewall
rear lamps to bed
bed to frame rail
cabin firewall to hood
I am going to make all the above, and cut out the white connectors and solder. and see if this makes any difference as it will.
NOT A GOOD START;
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[absent grounds...]
battery to right (passenger) frame rail - this one is important as the primary extension of the main vehicle ground
back right cylinder head to cabin firewall - this primary ground ensures the cabin is adequately grounded in support of all interior and cabin mounted electrical appliances
rear lamps to bed - ensures the rear lamps are suitably grounded; alternatively, you can ground the rear lamps directly to the right frame rail
bed to frame rail - ensures the bed is suitably grounded in support of the rear lamps
cabin firewall to hood - (optional) helps manage radio "zzzzzzz" and provides a stable ground for an optional hood mounted engine compartment lamp
...NOT A GOOD START;
Actually, you are off to a GREAT start!
The purpose for all of the primary ground connections is to ensure that "ground" is zero [earth] everywhere in the vehicle. If that zero reference isn't consistent and at the same electrical potential throughout, all manner of ill will can befall you. You'll begin to believe your truck is haunted! Good grounds are vital for a happy vehicle!
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i have fabricated new earths/grounds that where missing from your list, and now have ZERO reading earth/grounds to all . I also have removed the white connectors, and have soldered them and shrink wrapped (pic 1). the problem still persists (hazards only fault)
pic 2 shows bulk head connectors,(4 wires right bulkhead connector rear lights, 5 wires left bulkhead connector front lights) due to the way this has been wired at the white junction box. only the white wire earths/grounds tie in to front and rear lights at this point. I am unsure as to the correct location of the 1n5402 diode as per your drawing, due to lack of front and rear tie-in
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Are the first and third pics of the same junction box, and does the junction box strictly serve the wires running to the rear lamps?
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yes the pics are the same junction box (drivers side fender)
both bulkhead connector wires enter this junction box
top entry is right bulkhead connector in and rear wire loom out
side entry is left bulkhead connector in
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(http://forum.73-87chevytrucks.com/smforum/index.php?action=dlattach;topic=35608.0;attach=37880;image)
Isolate the brown wire that splits and runs to the left and right forward lamps. The brown wire is the park/running lamp feed. Do any wires from the rear lamps splice into this brown wire?
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left bulkhead connector wires are;
blue = left indicator blue front loom wire
dark blue = right indicator blue front loom wire
dark brown = front park lamps black front loom wires (dark brown is park/running lamp feed)
brown = low beam brown front loom wire
green = high beam green front loom into relay
right bulkhead connector wires are;
dark brown = park lamps blue rear loom wire (dark brown is park/running lamp feed)
yellow = left indicator red rear loom wire
dark green = right indicator black rear loom wire
green = reverse/backup yellow and green rear loom wire
NO rear lamps tie-in to the brown wire
ONLY the white ground/earths tie-in to front and rear loom
I have not isolated the brown wire at this point !!
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(http://forum.73-87chevytrucks.com/smforum/index.php?action=dlattach;topic=35608.0;attach=37902;image)
Is the wire circled in yellow the dark brown wire coming from the "left bulkhead" connector? If "Yes," place the diode here with the band orientated toward the forward lamps.
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yes that is the left bulkhead connector in, and I have installed the diode toward the front lamps.
and everything is working FINE :) NO RED FLASHING
I would just like to thank you BD for all your time and expertise with this install I would not have done it with out you.
many thanks regards neil
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You are quite welcome, Neil. I'm happy to help.