72 K 20 Electrical Trouble - The 1947 - Present Chevrolet & GMC Truck Message Board Network

reysteve · 10-30-2009, 04:08 PM

Hi,
I am new here and I did search for people having similar trouble but I could not find anything.

My problem: My truck will not turn over as if the battery is dead, the battery is not dead. THe junction block has power, the headlights dont come on, the brake lights work. There is power at the ignition switch. The truck ran fine and then I parked it and when I came back I get this weirdness. I tried all of the things that I could think of. Thanks for any help.

If you need it:
The truck is a 72 K20 with a 350, manual trans. One owner, my dad gave it to me, he bought it new so it is pretty much stock

smn69 · 10-30-2009, 04:22 PM

Check all of your grounds and make sure you have good connections and clean wires. If I remember correctly: core support to frame, Neg. side of battery to block, firewall to block, passenger side under cab to frame, and bed to frame at the back.

mclairmo · 10-30-2009, 07:13 PM

Make sure you have 12.5 volts at the battery with the engine off. If so, then the starter may be faulty. You can remove it and bench test it. I just hook up my booster cables to the battery and the starter to see if the pinion will pop out and spin.

rwolf9653 · 10-30-2009, 07:17 PM

It sounds like a connection/ground problem. The headlight switch should have nothing at all to do with your ignition switch or starter.
Check your grounds as suggested above, and remember that the cables are getting old so they may look good, but actually not be working as well as they should.
My 72 had a glass fuse for the ignition on the firewall but it did not look stock, check and see if you have a fuse that is blown.

Truck Dr. · 10-30-2009, 08:04 PM

You said that the headlights did not work, makes sure 12 v at the bat. if so check fusible links, at starter and also junction by master cylinder....

Dave

roger0080 · 10-31-2009, 02:25 AM

FWIW I had it where I parked it at college, came out and nothing happened. No headlights. No starter/solenoid engament, nothing.

Turned out it was the negative battery cable that was bad. Replaced the cable and she started.

Truck Dr. · 10-31-2009, 07:06 PM

At least it's fixed.

reysteve · 11-02-2009, 11:40 PM

Quote:

Originally Posted by roger0080

FWIW I had it where I parked it at college, came out and nothing happened. No headlights. No starter/solenoid engament, nothing.

Turned out it was the negative battery cable that was bad. Replaced the cable and she started.

Yep that was my problem, I replaced it and now it starts! Now to put everything back! Thanks for all of your help

10-30-2009, 04:08 PM	#1
reysteve Registered User Join Date: Oct 2009 Location: Southern CA Posts: 2	72 K 20 Electrical Trouble Hi, I am new here and I did search for people having similar trouble but I could not find anything. My problem: My truck will not turn over as if the battery is dead, the battery is not dead. THe junction block has power, the headlights dont come on, the brake lights work. There is power at the ignition switch. The truck ran fine and then I parked it and when I came back I get this weirdness. I tried all of the things that I could think of. Thanks for any help. If you need it: The truck is a 72 K20 with a 350, manual trans. One owner, my dad gave it to me, he bought it new so it is pretty much stock

10-30-2009, 04:22 PM	#2
smn69 Registered User Join Date: Oct 2007 Location: Orem, Ut Posts: 132	Re: 72 K 20 Electrical Trouble Check all of your grounds and make sure you have good connections and clean wires. If I remember correctly: core support to frame, Neg. side of battery to block, firewall to block, passenger side under cab to frame, and bed to frame at the back.

10-30-2009, 07:13 PM	#3
mclairmo Registered User Join Date: Jan 2006 Location: Take Off Posts: 1,908	Re: 72 K 20 Electrical Trouble Make sure you have 12.5 volts at the battery with the engine off. If so, then the starter may be faulty. You can remove it and bench test it. I just hook up my booster cables to the battery and the starter to see if the pinion will pop out and spin.

10-30-2009, 07:17 PM	#4
rwolf9653 more ideas than money Join Date: Dec 2008 Location: spring grove, pa Posts: 1,068	Re: 72 K 20 Electrical Trouble It sounds like a connection/ground problem. The headlight switch should have nothing at all to do with your ignition switch or starter. Check your grounds as suggested above, and remember that the cables are getting old so they may look good, but actually not be working as well as they should. My 72 had a glass fuse for the ignition on the firewall but it did not look stock, check and see if you have a fuse that is blown. __________________ Randy 1948 Chevy 3100 5 window 1966 Chevy C30 Dually 1967 Chevy K10 1972 Chevy K20 1972 Chevy C10 1972 Chevy K5 Blazer 1987 Chevy V10 2003 Chevy Suburban

10-30-2009, 08:04 PM	#5
Truck Dr. Registered User Join Date: Oct 2009 Location: Rio Rancho NM Posts: 74	Re: 72 K 20 Electrical Trouble You said that the headlights did not work, makes sure 12 v at the bat. if so check fusible links, at starter and also junction by master cylinder.... Dave __________________ Dave & Marilyn in Rio Rancho NM....1967 Chevrolet C-10 long step side.....250 3 spd. ..... 1968 Chevrolet C-10 long step side.....325 hp 350 4spd.....3" Exhaust....etc. 1965 Chevrolet Suburban K-10....292 4spd....cam....etc. Bow Tie Baby

10-31-2009, 02:25 AM	#6
roger0080 Registered User Join Date: Nov 2000 Location: Carver County, Minnesota, USA Posts: 627	Re: 72 K 20 Electrical Trouble FWIW I had it where I parked it at college, came out and nothing happened. No headlights. No starter/solenoid engament, nothing. Turned out it was the negative battery cable that was bad. Replaced the cable and she started. __________________ 72 Chev C-10 90% restored (former AZ truck) ... 71 Chev K-20 Cheyenne my vacation crusier... 72 Chev C-10 Now retired and striped after many faithful miles... 72 GMC 1500 Retired to the junk yard after bought new in '71...

10-31-2009, 07:06 PM	#7
Truck Dr. Registered User Join Date: Oct 2009 Location: Rio Rancho NM Posts: 74	Re: 72 K 20 Electrical Trouble At least it's fixed. __________________ Dave & Marilyn in Rio Rancho NM....1967 Chevrolet C-10 long step side.....250 3 spd. ..... 1968 Chevrolet C-10 long step side.....325 hp 350 4spd.....3" Exhaust....etc. 1965 Chevrolet Suburban K-10....292 4spd....cam....etc. Bow Tie Baby



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