Ad Radar
Custom Classic Trucks
Click here to find out more!

59 fleetside electrical question.

Custom Classic Trucks
Item Posts    Sort Order

59 fleetside electrical question.

mklomps mklomps
New User | Posts: 7 | Joined: 05/12
Posted: 05/15/12
07:53 AM

my father and i just finished a project on this truck. he is retired so he did most of the work. the question i have is that the truck runs fine and all looks normal until the lights are turned on. during normal running the amp meter stays around the 50% mark. when we turn the head lights on the amp meter goes up to 3/4. but everything still seems to be operating ok. when the high beems are turned on (by the button on floor) the amp meter goes all the way up (to the right) after about 2-3 minutes in this condition the lights go out and then come back on. they will cycle like this on about 10 sec. cycles. this happens at idol or running down the road. a new wiring harness was installed in this truck and i havent looked into detail. any ideas?  

waynep71222 waynep71222
User | Posts: 106 | Joined: 04/12
Posted: 05/16/12
07:12 AM

it sounds like you have a possible short to ground somewhere in the wiring for the lighting ..

does THIS truck have a factory harness from 1959..   so a conventional 59 truck wiring diagram can be used..

most headlight switches have a thermal circuit breaker built in..  

if you don't have an AC/DC  AMP clamp...   you will want to disconnect one bulb or circuit at a time from the head light switch till you find the load returns to normal..

you could have a spring in a bulb socket contacting the back of a bulb contact terminal and dragging down the circuit..

what....    inside the most bulb sockets... its set up like this

wire...     housing,    spring...  circuit board with mushroom terminals crimped to the wire.. bulb  contact end...

you could also .  have a serious water damage short in the dimmer switch through the floor..

you might get under the truck and unplug this and see if the load vanishes...

your dimmer switch might be a 3 finger with screw terminals sticking out..

Duralast/Dimmer Switch
For your 1959 Chevrolet Truck 3100 1/2 ton P/U 2WD 4.6L 2BL OHV 8cyl
Price: $15.99
Part Number: UDS414  

waynep71222 waynep71222
User | Posts: 106 | Joined: 04/12
Posted: 05/16/12
07:28 AM

if you have a digital volt meter..  you can pick up a low amp current probe from aeswave dot com.. under 100 bucks.. makes tracing electrical loads easier.. good for up to 40 amp or so..  but great for finding parasitic loads..

07 60 Thumb

or a stand alone AC DC amp clamp at the home depot..   please.. read the specs carefully .. i saw several listed as AC DC.. that really did not seem to have a DC setting at least in the image..  

mklomps mklomps
New User | Posts: 7 | Joined: 05/12
Posted: 05/16/12
10:57 AM

Thanks for your help. I do commercial AC work for a living, so i have the tools to check it, just not real familiar with the aouot side and where to start. the wiring harness has been replaced. also on google i saw a few things that mentioned a shunt in the amp. meter circuit. ?? not sure if thats it but what do you think.  

waynep71222 waynep71222
User | Posts: 106 | Joined: 04/12
Posted: 05/16/12
07:28 PM

with an amp clamp...

should be quick to grab some amperages..

headlights as i recall are like 10 to 14 amps..

there is a shunt somewhere in that system...

i don't have a 59 wiring diagram infront of me..

was it a STOCK reproduction harness you installed. or a universal installation..

there are SO many ways to go wrong...

with your digital volt meter.. i would like you to run a voltage drop test...   practice on another car first..

engine running .. headlights on...   digital volt meter set to 20 volts DC scale...

1. test between the Negative battery post and the Positive battery post..  14.1 to 14.8 volts..

2.  test between the Negative battery post and the engine block.. 0.04 volts is expected.

3. test between the negative battery post and the body.. probably the cab..  0.02 volts is expected..

4.  test between the ENGINE BLOCK and the body.. usually at the firewall.. 0.02 volts is expected..

if you get 0.00 on the last 3 tests.. reset the digital volt meter to 2 volts DC and retest the last 3..  0.00 is a bad result..  if the engine is running and the headlights on.. this is measuring the Voltage drop through an ACTIVE circuit..    you probably already do this in your HVAC life...  man does it solve electrical issues..  if you get more than that.. bad ground between those parts..

this test like i say takes about 2 minutes..  i can do it in under a minute.. so you might want to try it.. on a different car.. then   on your pickup.. with a friend working the headlight switch off and on between tests..

i have a friend with a 98 C2500.. test 4 was 8.5 volts between the engine and the body.. wow what a difference that made when i fixed the ground properly...

another friend with a 92 camry.. just cleaning the grounds increased the charging voltage from a fluttering 14.1 to a rock stable 14.6..  camry has 6 ground wires to the engine that i cleaned.. and that did not include the ones from the fuel injection harness..  

mklomps mklomps
New User | Posts: 7 | Joined: 05/12
Posted: 05/17/12
07:22 PM

the harness is a Universal. im not familiar with the shunt or where it would be. do you have any more info you could share with me. also the new dash panels have voltage readouts instead of amper. do you have any pref. on the two. im not opposed to buying a new dash cluster.  we had a "hot Rod" guy do the wiring. i thought of the groung thing and used some jumper cables to go from the battery to the block to the cab. nothing changed. ill do the voltage drop test tomorrow, already chedcked battery voltage its at 14.5. thanks again for your help.  

mklomps mklomps
New User | Posts: 7 | Joined: 05/12
Posted: 05/17/12
07:25 PM

forgot to tell you that i checked the dimmer switch and its ok. pulled plug off checked to ground with meter and also put a jumper wire in the plug to make dimm and bright lights. the problem didnt change. also the light switch on dash is new.  

waynep71222 waynep71222
User | Posts: 106 | Joined: 04/12
Posted: 05/17/12
07:57 PM

talk to the manufacturer of the gauge and to the manufacturer of the wiring harness..

i will be glad to trouble shoot.. but its REALLY hard over the web.. when the parts are Universal replacements.. NOT an exact OEM...

post some of your part numbers...   which of the over 100 different models of wiring harness...

which of the gauges..

i personally HATE amp meters...   i like volt meters.. either a good digital version or a Numbered analog.. so i know exactly what the current voltage is..

in some of my research it looks like the shunt might be in the gauge..

amp clamp to find massive loads... is the easy way to figure things...

the digital amp meter.. might require a remote shunt...   what gauge are the wires going to it??

post some info on what parts you have installed..  

waynep71222 waynep71222
User | Posts: 106 | Joined: 04/12
Posted: 05/17/12
08:03 PM

an amp clamp is the way to go..

i would bet that you would use this weekly in your HVAC work...  

mklomps mklomps
New User | Posts: 7 | Joined: 05/12
Posted: 05/18/12
07:51 AM


mklomps mklomps
New User | Posts: 7 | Joined: 05/12
Posted: 05/22/12
07:06 AM

thank you waynep77. the prob was that the new switch i bought for the lights is a 59 replacement and it has an overload type swicht in it. since the new headlights are halogen and pull more amp. than the originals the switch overload was seeing the increased amp. draw and causing them to shut off. wired around the built in overload. hope switch is enough to handle new lights.  thanks again  

waynep71222 waynep71222
User | Posts: 106 | Joined: 04/12
Posted: 05/23/12
07:03 AM

wiring around this one way... the better way is to use one a pair of relays to drop the load closer to the front of the truck....

rewiring .    
low beam wire from switch to PIN 86 .  

ground PIN 85...

pin 30 to a fusible link .. or circuit breaker..  probably 6 inches of 16 gauge fusible link.. or a 25 amp self resetting circuit breaker hooked up to the positive battery

pin 87A to the headlight low beam circuits..

you might also want to increase the size of the ground wire connection to the halogen lights..  and verify the battery negative cable is also grounded to the body properly..

same relay install for the high beam side... use the same relay.. as you only have HIGH or LOW beams.. NOT both..

when doing things with RELAYS to control the headlights..  one can get really creative..

you can hook up reduced brightness daytime running lights..   flash to pass on the high beam side..  and get much brighter lights...  this all requires some study of how various cars do this..  there are modules available to do some of this..  

if interested.. just post..  its complicated..  but can be done..  

mik13usa mik13usa
New User | Posts: 44 | Joined: 08/10
Posted: 03/22/13
05:49 PM

Wayne is right,
 The relays will take the load off the switch and I believe there is a kit from Eckler's that is designed for the '59