electrical help... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bubbards2000 · 01-30-2003, 11:52 PM

I need some major help with my 72 I just bought. I looked in a chiltons but their wiring diagrams didnt really help me. After 5 owners there is so many wires, I dont even know what to do with them. I am having a problem with my rear lights (backup, tail, parking and brake). Anyone know any good places for wiring diagrams either on the net or not. Thanks, Justin.

TERRYP · 01-31-2003, 02:31 AM

http://morechevys.homestead.com/fileindex.html

'72 Shorty · 01-31-2003, 02:36 AM

Link don't work for me.

As for tail light probs, I had some strange ones that ended up being a bad NEW turn sig switch, but the prob didn't show itself for the first 6 months. Had me perplexed for a week.

Something else to look at besides just wires.

Fred T · 01-31-2003, 02:50 AM

Link worked for me. Go here http://www.geocities.com/chevroletc1070/wiringdias.html
for 67-72 diagrams

'72 Shorty · 01-31-2003, 03:06 AM

Sorry, computer didn't like it the first time. works for me now too.

barn9 · 01-31-2003, 04:19 AM

You have to remember that you are dealing with 30 year old wire, and probably several backyard fixes, trailer lights, etc. I fought the same problems for several years, and got tired of trying to track down all the never-ending crap. Bit the bullit and bought a new rear wiring harness with the trailer light adaptor that plugs into the harness plug, and have not had a problem since. The harness wasn't cheap, but neither are traffic tickets.

70c10 · 01-31-2003, 08:49 AM

I recently solved a similar problem by replacing my turn signal switch.

Longhorn Man · 01-31-2003, 02:40 PM

Wow, amazed this hasn't been said yet, but double check your grounds, esp if you have the wooden bed floor.

**COBALT** · 01-31-2003, 03:03 PM

Yeah, longhornmail is right. About 90% of these electrical problems are lost or faulty ground.

As soon as you start looking at wiring diagrams you'll soon realize that they're split into distinct sections: rear (for brakes, back-up, license plate lights, rear turn-signals, rear side-markers [if applicable]), front (headlights, front turn signals, front side-markers [if applicable]), engine (battery, alternator, starter, coil), and dash (instruments, radio, cigarette lighter, washer motor, high beams, etc. etc.).

It helps me to always think of these circuits as their own beasts. Get a good volt meter that reads current and resistance as well. Follow the directions. Also get a basic 12 V test light (the kind that has a positive clip, and a screw-driver like probe with the 12 V bulb in the handle). Also, make some jumper wires (3", 12" and a 36" wire with either aligator clips or U shaped connectors). It makes checking bad wires WAY easier.

The second link previously posted was the most help for me. Good luck.

ChevLoRay · 01-31-2003, 07:54 PM

This website offers wiring harnesses for our trucks (and many other vehicles). They have an excellent product, with all wire colors being the same as original. Connectors are perfect and all original-type retainers/clips/etc., are attached.

If you don't want to, or can't afford new wiring, just remember that at some time, you may have to do so, or risk additional problems, fire hazards, etc. If you are planning to do a restoration, or restification, you should budget this item in your "to do" list.

01-30-2003, 11:52 PM	#1
bubbards2000 Registered User Join Date: Jan 2003 Location: Albuquerque, NM Posts: 2	electrical help... I need some major help with my 72 I just bought. I looked in a chiltons but their wiring diagrams didnt really help me. After 5 owners there is so many wires, I dont even know what to do with them. I am having a problem with my rear lights (backup, tail, parking and brake). Anyone know any good places for wiring diagrams either on the net or not. Thanks, Justin.

01-31-2003, 02:31 AM	#2
TERRYP GYRO GEARLOOSE Join Date: Jun 2000 Location: Nevada City, CAEverett, WA Posts: 361	http://morechevys.homestead.com/fileindex.html __________________ Nevada City, CA Everett, Washington 57 3/4 rat, 235, 3spd 66 C-10 Panel, SWB. 350 from '68, 200R4 tranny, 3.07 rear ratio, restoring 68 C10 LWB 350 4spd, 4.56 rear dump runner 82 Camaro, 305, THM-200-R4 84 Monte Carlo 305 TH350, land tuna 85 Tercel SW, snow runner DISGRACED OUTLAW MEMBER OF THE DRUM BRAKE CLUB Last edited by TERRYP; 01-31-2003 at 02:34 AM.

01-31-2003, 02:36 AM	#3
'72 Shorty I finally got an avatar Join Date: Jan 2003 Location: Cheney, WA Posts: 180	Link don't work for me. As for tail light probs, I had some strange ones that ended up being a bad NEW turn sig switch, but the prob didn't show itself for the first 6 months. Had me perplexed for a week. Something else to look at besides just wires. __________________ -72 C-10 short step (straight line only) 12.922/102.28 -69 C-20 on Propane (DD) -69 C-10 -56 Mack B-753LS (tow rig) -94 Chev K2500 Short Ex-Cab -89 Isuzu Trooper...Kinda -03 Kawasaki KFX-400 -05 Suzuki DRZ-400S

01-31-2003, 02:50 AM	#4
Fred T Cantankerous Geezer Join Date: Aug 2002 Location: Bel Aire, KS Posts: 6,264	Link worked for me. Go here http://www.geocities.com/chevroletc1070/wiringdias.html for 67-72 diagrams __________________ Fred There is no such thing as too much cam...just not enough engine.

01-31-2003, 03:06 AM	#5
'72 Shorty I finally got an avatar Join Date: Jan 2003 Location: Cheney, WA Posts: 180	Sorry, computer didn't like it the first time. works for me now too. __________________ -72 C-10 short step (straight line only) 12.922/102.28 -69 C-20 on Propane (DD) -69 C-10 -56 Mack B-753LS (tow rig) -94 Chev K2500 Short Ex-Cab -89 Isuzu Trooper...Kinda -03 Kawasaki KFX-400 -05 Suzuki DRZ-400S

01-31-2003, 04:19 AM	#6
barn9 Half a bubble off! Join Date: Jun 2000 Location: Winfield, Ks, USA Posts: 5,588	You have to remember that you are dealing with 30 year old wire, and probably several backyard fixes, trailer lights, etc. I fought the same problems for several years, and got tired of trying to track down all the never-ending crap. Bit the bullit and bought a new rear wiring harness with the trailer light adaptor that plugs into the harness plug, and have not had a problem since. The harness wasn't cheap, but neither are traffic tickets. __________________ Just call me LB. '71 Cheyenne, 402BB, hauls blondes, brunettes, or redheads.

01-31-2003, 08:49 AM	#7
70c10 67-72 Addict! Join Date: Feb 2002 Location: The TAX State! Posts: 7,856	I recently solved a similar problem by replacing my turn signal switch. __________________ Jim 1970 C/10 Fleetside w/Ghost Flames Lowered 4.5" front and 4" rear (Raked) 355/350 Turbo w/shift kit 10" Redneck Performance Verter w/2500 stall Hooker Super Comps part#2808-1 Performer RPM Air-Gap 12 Bolt w/3:73 gears- Eaton Posi Comp Cams XE262 with 1.6 Crane Energizers, Road Demon 625 and Brodix IK 180 heads

01-31-2003, 02:40 PM	#8
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Wow, amazed this hasn't been said yet, but double check your grounds, esp if you have the wooden bed floor.

01-31-2003, 03:03 PM	#9
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	Yeah, longhornmail is right. About 90% of these electrical problems are lost or faulty ground. As soon as you start looking at wiring diagrams you'll soon realize that they're split into distinct sections: rear (for brakes, back-up, license plate lights, rear turn-signals, rear side-markers [if applicable]), front (headlights, front turn signals, front side-markers [if applicable]), engine (battery, alternator, starter, coil), and dash (instruments, radio, cigarette lighter, washer motor, high beams, etc. etc.). It helps me to always think of these circuits as their own beasts. Get a good volt meter that reads current and resistance as well. Follow the directions. Also get a basic 12 V test light (the kind that has a positive clip, and a screw-driver like probe with the 12 V bulb in the handle). Also, make some jumper wires (3", 12" and a 36" wire with either aligator clips or U shaped connectors). It makes checking bad wires WAY easier. The second link previously posted was the most help for me. Good luck. __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

01-31-2003, 07:54 PM	#10
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	www.wiringharness.com This website offers wiring harnesses for our trucks (and many other vehicles). They have an excellent product, with all wire colors being the same as original. Connectors are perfect and all original-type retainers/clips/etc., are attached. If you don't want to, or can't afford new wiring, just remember that at some time, you may have to do so, or risk additional problems, fire hazards, etc. If you are planning to do a restoration, or restification, you should budget this item in your "to do" list. __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.

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