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Electrical difficultys, Truck won't start any more

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Electrical difficultys, Truck won't start any more

beachj89 beachj89
New User | Posts: 6 | Joined: 03/13
Posted: 03/30/13
12:04 PM

I am new to restoring older vehicles and I recently bought a 74 Chevy K10. I Drove the truck 200 miles home with no problems to the motor or ignition, but when I went to trying to track down a problem with the brake light/blinker I unhooked the ground cable and forgot to hook it back up, it sparked a few times and when I shut everything down the lights were glowing hot. That being said now the truck wont start and the battery will not hold a charge, I'm going to buy a new battery this afternoon and change out the turn signal switch, but I still don't think that is the root of the problem. When I hook up the battery charger and turn the ignition it just clicks and blows the acc fuse.

Any advice would be appreciated I'm kind of new to all this and I bought the truck to help teach myself with.
Thank you  

76Skylark 76Skylark
Guru | Posts: 854 | Joined: 12/11
Posted: 03/30/13
12:36 PM

the Killed Battery won't let the low amperage of the charger get to the starter. That's the jest of it but wayne will fill in the Details he can explane better than I.  

87vorteccamaro 87vorteccamaro
New User | Posts: 41 | Joined: 03/13
Posted: 03/30/13
12:43 PM

Bypass the battery all together just to get it started??  

pepsi1 pepsi1
Guru | Posts: 1718 | Joined: 09/11
Posted: 03/30/13
03:10 PM

When a vehicle sits for any length of time things happen really quick. All you need is one mouse making home in the wires and that could be a nightmare.
Before you hook up your new battery;
Check for poor grounds, loose connections, spliced wires, where a mouse may have chewed through etc. erc. With that all said.



1.remove the wires from your starter, Clean them really good, (I've seen then over heat) there are some factory splices (Fusiable Links) that burn out. If there are any in your unit. Give them a tug some will be so brittle they fall apart others may look good but are no good.(Some are actually turn green) from oxidation over time. They can open connection when they get hot and close connection. Shuting off all the electrical power down. Then by the time the tow truck comes it starts up.... Seen it many times. That is if they have those splices...

2.Clean all those wires and connection. Power goes to your fuse box VIA the starter cable.

3.Make sure you have you don't have any OPEN or BLOWN Fuses. Look for rusted terminals on the ends, just that little bite of resistence could cause electrical problems, that will drive you crazy.

4.Hook up the battery. (If the engine doesn't crank)

5.For this you will need a helper.

6.With a good test light

7.Make sure you have battery voltage to the BIG heavy red power lead to the starter. Thats what you want

8.Now go to a smaller wire. Now have your helper turn the ignition key. (If no power trace the wire) Now go to the other wire unless they

There are a few things that can cause the engine not to start.

1.After installing a new battery have a helper turn thr key to start, while you lightly tap the starter. Sometime the starters get hung up. Look to see if the support is on the front of the starter. If its missing you need to replace it. That starter will bend if not suported from the nose.

2.Ignition switch maybe no good

3.Nuetrial/Safety switch could be faulty....

4.Almost any power that goes to the fuse box comes through the starter power. On the older cars there isn't a power/distribution block. So look for fusiable links close to the starter area....


zman123 zman123
Enthusiast | Posts: 531 | Joined: 06/08
Posted: 03/30/13
08:07 PM

and remember, GROUND CABLE OFF FIRST AND ON LAST!! Burned out fusible links will stretch when pulled on. Depending on how old and what kind of shape thay are in. New battery cables (both of them) are way cheaper than new starters and batteries so if you want to start replacing things, start with the cables first.  

waynep712222 waynep712222
Enthusiast | Posts: 251 | Joined: 03/13
Posted: 03/30/13
10:19 PM


notice that the wire that feeds the inside of the truck.. also connects to the side plug on the alternator..

the output wire on the alternator is connected to a DIFFERENT fusible link...

this lets you probe the back of the alternator to test one fusible link.. and the red wire into the side to test the other.. both should have constant power...

Starterwiring 1

don't forget.. there is a terminal block on the firewall with additional fusible links and that may need to be taken apart and the terminals wire brushed..

this is for a 77 to 80 chevy truck.. but i would bet that yours is very simple

77 80 Chevytruck Fusible Links

great post bob..  

beachj89 beachj89
New User | Posts: 6 | Joined: 03/13
Posted: 03/31/13
09:56 AM

I went threw the grounds, and changed the battery and it runs again!! Now i'm back to the original problem, the acc fuse keeps blowing and the brake light/blinker on the drivers side will not work, all other lights work fine, any suggestions?
Take that back the back up lamps do not work either, what does the acc fuse on the top right of the fuse box power?  

68scott385 68scott385
Guru | Posts: 1990 | Joined: 10/09
Posted: 03/31/13
01:16 PM

If the fuse keeps blowing you have a shorted circuit. You need to trace it with a continuity meter to see where it's broken/shorting.

Have you checked all the bulbs to see if that's why they are not working? Check the ground(s) for the rear harness too, it's typically under the vehicle, exposed to the elements.

Have you checked to turn signal connecter under the steering column? I have seen them partially plugged in, causing one side to work while the other does not.  
68scott385 68scott385 68scott385

waynep712222 waynep712222
Enthusiast | Posts: 251 | Joined: 03/13
Posted: 03/31/13
01:42 PM

well.. i looked at the 74 GMC pickup wiring diagram... same as the chevy ..

it shows the ACC power going to the upper 2 fuses next to the hazard flasher... and the hazard flasher as the top fuse.. but it shows the second fuse down on the right  going to the wipers..

i see from the IGN3 wiring that one goes to the lower left fuse.. but that goes to the headlight switch.. probably for the TAIL lights..

can you describe the location of the fuse that blows??? so i can compare it to my wiring diagram.

on the turn signal connector.. there is a white wire... that comes from the brake light switch.. foot on the brakes.. should have power there when probed with a test light...

next to that is the dark green wire  that goes to the rear stop and tail lights.. probably on the right side..

next to that is the YELLOW wire.. that goes to the rear stop and tail lights probably on the left side...

if you depress the brake pedal.. and the turn signal is in the off position.. you should have power on the white wire.. on the dark green and yellow wire also.. this proves that some of the contacts in the turn signal switch work properly...

now.. with the test light in the yellow wire...  turn the turn signal switch to the right.. and depress the brake.. does the test light come on with a solid light...

move the turn signal switch to the left..  and the test light should start flashing..

move the test light to the dark green wire  and move do the same test.. this time.. when the turn signal switch is in the right turn position. it should flash.. in the left turn while your hand is on the brake pedal .. is should be a solid light..

this proves the turn signal switch works properly.. at least for the rear lights.. at the connector..

now.. do you have some spare wire around..  several feet... strip back several inches..   remove the bulb.. wrap it around the base of the glass.. so its right at the top of the brass shell.. twist the bulb.. so the wire loop tightens..   now.. reinstall the tail light bulb into the socket..   find a good ground like the back bumper to ground the wire to.  or someplace else handy.. i have gone as far as running my long jumper cables back there.. just having the negative one hooked up... so i know i have a good NEGATIVE/ground connection to test...

the bulbs are supplied power thru the ground side..   from the battery negative to a ground connection to the frame... from the frame to a ground strap to the bed... from the bed to the mounting screws or just contact between the tail light housing and the bed..   no ground.. no tail or turn signal light operation...

do you have a wiring diagram at all.. perhaps this will help..

74 GMC PU Wiringdiagram Zpsf2f1be84  

beachj89 beachj89
New User | Posts: 6 | Joined: 03/13
Posted: 05/04/13
07:49 AM

Thank you for all your help I cleaned up the contacts on the rear plug and the taillights started working, as for the windshield wipers I found a loose wire under the hood. Thanks for the help!  

Mikelalen Mikelalen
New User | Posts: 2 | Joined: 12/13
Posted: 12/19/13
08:06 PM

I have a 1986 chevy k 10 starts and runs  my charging system is charging low my head lights and tail lights won't turn on flashers and breaks lights work new alternator regulater is in alternator cleaned all my conections changed relays no fueses have blown I'm confused  help would be great  

wayne712222 wayne712222
User | Posts: 205 | Joined: 10/13
Posted: 12/20/13
03:49 AM

I have a 1986 chevy k 10 starts and runs  my charging system is charging low my head lights and tail lights won't turn on flashers and breaks lights work new alternator regulater is in alternator cleaned all my conections changed relays no fueses have blown I'm confused  help would be great  

start with a voltage drop test..

this is printable...




post results by number...





you will also want to measure from the stud on the back of the alternator to the battery positive post with the meter set at 20 volts DC.. post that result also..

with these numbers.. i can direct you to the next set of testing..

i will drop in again when you answer...  

Mikelalen Mikelalen
New User | Posts: 2 | Joined: 12/13
Posted: 12/20/13
09:45 AM

1 checks out alternator reads low charge about 11volts the same time the bat reads 13.5 while truck runs
2resistance checks Out on everything  and just to add I changed my light switch I'm concerned its my bright switch/ dimmer switch if it was wouldn't a fuse blow?  

wayne712222 wayne712222
User | Posts: 205 | Joined: 10/13
Posted: 12/20/13
12:03 PM

13.5 is too low an alternator output... did you perform the engine off.. headlights on for a minute then turned off voltage test on the battery .???  if the battery tests much below 12.5 volts.. it will prevent the alternator from putting out the proper 14.1 to 14.6 volts DC as the current from the alternator is being used to recharge the battery instead of building up to the slightly higher voltage..

were you able to use a hand held digital volt meter and perform the voltage drop test i listed above??? to verify the grounds are properly attached..

post some results of that test. it only takes a minute or two to run it..

another thing.. how is the alternator belt tension.???  engine off.. key in your pocket..  that model probably has the round plastic and steel alternator fan blade behind the pulley. if it had exposed fins.. i would have you push a fin with your thumb and see if the alternator slips inside the belt.. you can use a 15/16" socket on the alternator pulley nut.. and check the belt tension.. the tension should be set so the alternator adjustment is just slightly tighter than when the belt slips without turning the motor..

if you go too tight. you burn out the alternator and water pump bearings..

if you go too loose.. the alternator slips and does not put out the proper amount of charge..


if you are looking at the volt meter on your dash board for test results.. it is not going to be as accurate as a 5 to 20 buck hand held digital volt meter ...


and just to add I changed my light switch I'm concerned its my bright switch/ dimmer switch if it was wouldn't a fuse blow?  

the headlight switch has several sources of power for the various outputs..

the headlights power comes in on its own wire and there is a circuit breaker in the headlight switch to protect the headlight wiring..

the tail lights get their own fused power wire coming into the headlight switch.

the instrument cluster lights use the tail light fuse circuit for power.. but the instrument cluster has its own fuse between the headlight switch and the instrument cluster illumination bulbs .

the dome lights circuit is grounded thru the headlight switch when the knob is turned all the way left.. the dome lights may share power with the tail light fuse output.. it varies from model to model..


not.. the headlight circuit coming out of the headlight switch goes to the dimmer switch.. either on the floor or on the side of the steering column. there the dimmer switch selects either the high beam circuit or the low beam circuit..

the headlights are grounded to the radiator core support.. via the black wire with a ring terminal .. if the ground connections are dirty.. either where the headlights plug in.. or where its grounded to the body.. or even more popular to fail is the small wire from the negative battery cable . that connects to the inner fender..

if that wire is not properly attached.. there won't be enough electrons in the body of the truck to go thru the headlights via the ground connection to make them shine bright..

this is why i ask you to perform a voltage drop test with a digital volt meter.

if you had gotten over 0.02 volts on test 3 or 4.. i would have had you take apart the ground wire connections and clean them with a stainless steel wire tooth brush from the hardware or paint store..

i found a 98 chevy truck that had low out put on the alternator.. and 2 and 3 were over 1.2 volts. but 4.. the ground connection between the engine and the body had 8.5 volts on it..  you would not believe how much better that truck ran when i had spent the 30 minutes and cleaned all the ground connections..  

wayne712222 wayne712222
User | Posts: 205 | Joined: 10/13
Posted: 12/20/13
12:23 PM

here is a view of the ground connections on a 92 chevy truck

Chevytruckgrounds92 Zpsa4aaf4c7

G105 is the ground connection from the battery to the body.
G101 is the ground connection from the headlights on that side of the truck
G100 is the ground connection from the battery to the engine..

there is another ground connection not shown that is a braided strap between the back of the engine and the firewall..

here it is on a jeep.
2000 Jeep Cherokee Sport Firewallground Zps7f7fb91c
the image below is how the battery cables are hooked up on an 85 86 chev truck

80S Chevy Truck Battery Cables

there should be something that looks like this on your firewall.. usually near the power brake booster.

with the engine off.. battery disconnected.. count the wires on yours.. take it apart and wire brush the ring termimals clean.. wire brush the stud and the nuts clean and reassemble.. then count the wires again to verify you did not miss one..

70 GM Terminalblock Zps6d4097f6  

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