Headlight Voltage

[bruceh]

I am working on improving my pathetic headlights.

I measured the voltage at the headlight (no load, headlight removed) and found it to be 11.8 volts while the battery was showing 12.2 volts. Is this 0.4 volt worth putting in relays and running some fat wires back to the battery?

I am looking for every improvement but don't want to waste time on something that won't help.

[KIX]

Quote:

Originally Posted by bruceh I am working on improving my pathetic headlights. I measured the voltage at the headlight (no load, headlight removed) and found it to be 11.8 volts while the battery was showing 12.2 volts. Is this 0.4 volt worth putting in relays and running some fat wires back to the battery? I am looking for every improvement but don't want to waste time on something that won't help.

If your battery was completely charged it should be reading about 12.5 vdc. if this were the case the .4v loss would give you 12.1 at the headlights. Your bulbs are probably rated to give correct illumination at 12.5 up to about 13.8 vdc. Your problem is that you're starting out with less than good voltage at your source. Have you checked the voltage at the headlights and at the battery with the engine running? IMHO putting in a relay is the only good and permanent, relatively easy solution. But, first you have to have a good supply voltage.

[Gary - K7GLD]

I totally rewired the headlights on our '88 Winnie using 10 ga wire and relays, drawing power directly from the battery - at the same time, I wired the lights so that the low beams stay on when I switch to the high beams - and I now have GREAT lights! An added bonus is that the OEM light switch only carries the current for the relay coils and clearance lights - so runs lots cooler...

[KIX]

!!!

[tderonne]

Rewiring with relays is quite common. There are even plug and play kits to do it. I've wanted to check my voltages and see if I need to do it...

Here's one for Fords:
http://www.gosracing.com/inc/sdetail/1983

(I've already disabled my daytime running lights, I'd have to look exactly how I'd have to wire it to make that kit work.)

[bruceh]

Quote:

Originally Posted by KIX If your battery was completely charged it should be reading about 12.5 vdc. if this were the case the .4v loss would give you 12.1 at the headlights. Your bulbs are probably rated to give correct illumination at 12.5 up to about 13.8 vdc. Your problem is that you're starting out with less than good voltage at your source. Have you checked the voltage at the headlights and at the battery with the engine running? IMHO putting in a relay is the only good and permanent, relatively easy solution. But, first you have to have a good supply voltage.

OK, good point about the starting voltage. I will re-measure the voltage differential with the engine running which is more realistic anyway.

Is the 'no load' measurement realistic or should I have a heaslights connected?

[John Hilley]

Quote:

Originally Posted by bruceh OK, good point about the starting voltage. I will re-measure the voltage differential with the engine running which is more realistic anyway. Is the 'no load' measurement realistic or should I have a heaslights connected?

It will be even lower with a load.

[DAN L]

i installed 4 sylvania silver star headlights. it made a BIG difference. no other changes were needed. i have driving and fog lights but have not installed them yet.

[dirko]

Hi Ho: I'm really confused about something. I assume that the engine was not running. So battery voltage of 12.2 volts is not unreasonable. Do you ever drive down the road with the engine not running? Normally when the engine runs, the battery voltage will be about 13.6 to 13.8 volts. If not, there is somethng wrong with the alternator or the batteries, usually the alternator.

However, what really has me confused is the "no load" reading. The only way to have a voltage smaller than the source (assuming the two things are connected) is for current to flow through a resistive path--no current, no voltage drop and it doesn't matter what the wire size.

I recommend a voltage reading taken right across the headlight with the engine running and the headlights on.

Good luck, Dirk

[bruceh]

I realize that you need to have the engine running to go down the road. What I was trying to determine was the difference beteen the base voltage and the voltage available at the headlights.

The main reason for the 'no load' measurement is that my whole headlight panel is sitting in my garage so that I can properly re-attach the mounting brackets. I realize that with a load the voltage drop will be even greater.

I was surprised that I had as much voltage drop as I did from what can only be a run of 16 ga wire and a headlight switch and maybe some random connectors.

Also, I admit to being medium lazy. Trying to measure headlight voltage with everything in place is contortionist stuff. I suppose that I could do it but it is so easy with the connectors just hanging there in front of me.

I am motivated to run some fat wires from a good power source (still working in this) to relays. Maybe I am being paranoid but I really want to fix this for keeps.

[John Hilley]

Quote:

Originally Posted by bruceh I realize that you need to have the engine running to go down the road. What I was trying to determine was the difference beteen the base voltage and the voltage available at the headlights. The main reason for the 'no load' measurement is that my whole headlight panel is sitting in my garage so that I can properly re-attach the mounting brackets. I realize that with a load the voltage drop will be even greater. I was surprised that I had as much voltage drop as I did from what can only be a run of 16 ga wire and a headlight switch and maybe some random connectors. Also, I admit to being medium lazy. Trying to measure headlight voltage with everything in place is contortionist stuff. I suppose that I could do it but it is so easy with the connectors just hanging there in front of me. I am motivated to run some fat wires from a good power source (still working in this) to relays. Maybe I am being paranoid but I really want to fix this for keeps.

If yours is like mine, the battery isolator and battery disconnect solenoids are on the fire wall. It would be easy to run a heavier wire from the chassis battery side of the isolator solenoid and mount a Bosch type relay near the headlights.

[bruceh]

Unfortunately, mine is not like yours. On my coach those things are in a compartment behind the step.

I have found two possible power sources.

The first is something called 'Aux A' and 'Aux B' that are blank and fused for 30 amps each. I am checking with the Workhorse forum to make sure that I understand it.

The second is the hydraulic motor for the levels/slides. It looks like a #4 or #6 wire and it is about two feet from the headlights. I can't think of a good reason to run this motor while using headlights.

[Stogie]

Would it be best to just replace the lamps first then go from there?

[bruceh]

Quote:

Originally Posted by Stogie Would it be best to just replace the lamps first then go from there?

Done that. It was the second thing that I did. First was to have a Workhorse dealer re-aim the headlights. Didn't want to bore everybody with the entire saga.