Backfeed of power from low beams to high

[Paaradigm64]

Hope someone has seen this problem. I have a low voltage back feed from low beam to high beam headlights when only lows on. I have checked all grounds, traced all wires to make sure they are hooked up correctly, replaced floor dimmer switch and headlight switch. If I disconnect any bulb in the system (4 light setup) then this back feed disappears. When I tested for voltage I find that both leads in main lights are energized when lows on. Other than pulling the entire wire harness out does anyone know why I am getting full voltage on both contacts at low beam setting or is this a norm and if I am getting this voltage then why would the highs only glow instead of full on? When I switch to high beams they glow nice and bright. If I run the car with the lows on it kills the battery.

 

[Steve340]

Have you got a short in one of the actual headlights?
Had this once.

 

[Paaradigm64]

Hey thanks for the tip I'll replace bulbs and see what happens!

 

[Steve340]

It sounds like your problem will be in the low/high pair.
If the bulbs do not work get in touch and I can step you through another check.
Hopefully it is not the wiring loom.

 

[Paaradigm64]

Hey I replaced the lamps but unfortunately it made no difference

 

[Steve340]

It looks like your problem is in the loom.
Do you want some instructions or would you rather go to an auto electrician?
Do you have a test light?
Steve

 

[Paaradigm64]

It would be great if you could pass on some tests. Yes I have a light and multi tester. Thanks for spending the time.
Scott

 

[Steve340]

Will do it is Monday morning here so I am off to work.
I will do something for you tonight.
Steve

 

[Steve340]

Things to check first.
Check the actual headlight plugs are not burnt or damaged etc.
Check the headlight wiring for burnt, cut, squashed, damaged or repaired areas of the loom. Check the loom right back to the firewall. These burnt or repaired areas are often the cause of problems.
Is the large plug at the firewall damaged?
Testing - use the test light
Disconnect and remove all the headlight bulbs.
3 pins have terminals for low beam, high beam and earth wire
2 pins have terminals for high beam and earth
Switch the headlights on to low beam and use the test light to probe for power in the terminals. In the 3 pin plugs on low beam power should only be found on one terminal and no power in the 2 pin high beam plugs
On high beam you should see power on one terminal at all four plugs.
On low beam if you find power on two terminals of the 3 pin headlight plugs you have a short in the wiring you need to find this. It could be anywhere even inside the car under the dash.
Who knows but let me know what you find will try to help.

 

[Paaradigm64]

hey sorry took so long to reply but like most people work comes first before play. I have power on both terminals of 3 pin hookups. I have looked at loom up to firewall and found no problems so I guess its inside to look further.

 

[Steve340]

Can you read an electrical schematic drawing? Do you have a service manual?
To test if the the fault is under the dash.
Test for high and low beam power at the firewall plug. You will need to determine the correct terminals to test.
Most likely will only be one high and one low. If you have no back feed at the firewall plug the problem is in the engine bay loom.