- Thread starter
- #21
canucksafari said:
So there is only one tapped battery. The high side is all 24v. It seems the headlight on the high side is wired to a harness. The low side is definitely tapped. Will keep on diggin.
24 volt system charging batteries at different rate (4 Viewers)
- Thread starter jetswim
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So there is only one tapped battery. The high side is all 24v. It seems the headlight on the high side is wired to a harness. The low side is definitely tapped. Will keep on diggin.
There will be one factory tap. This tap supplies 12V to the relay which then supplies the 12V you see on each headlight.
I thought I read in one of the prior posts there were two taps and two wires headed to the headlights and horn (one from each battery). Ignore that then.
gb
- Thread starter
- #23
Greg_B said:
Yes, ignore that. There is only one tap.
I noticed today that with the headlights on the voltage rises on the high side battery and drops on the low side battery.
Indeed, there is one factory 12v tap and that is for headlights. This tap is on the low side battery.
That was my assumption too. 12v from each battery to each headlights and horn to keep the batteries even.. I assumed it was a tap from the low batteries hot (not ground) side, and one from the high side's ground (not 24v) side.
No. I believe that this system utilizes a 'voltage differential' for it's lighting, where the differential is 12v between wires, so this pair has 24v and 12v for one side and the other has 12v and 0v. both are fed 12v power.
Having said all this, I am no electrical guy. I'm sorting it as I go.
That's pretty much it, as shown by the readings you got when you checked your headlight pins. One headlight uses the 24V side (with 12V as the neutral) and the other side uses the 12V tap, with 0V as the neutral. Thereby balancing the load on both batteries.
All of the Cdn spec 24V trucks use this "evil center tap" system to balance the load and be able to run 12V headlights.
gb
bj40green
Tssss, tssss
conversion to 24v lightbulbs
Hi everybody, maybe the pic below can shine a light and be of help for you guys. The top part is the situation as Mr Toyo designed it.
The bottom part is the change to 24V light bulbs. It's pretty simple. There are only two changes to make.
The DS needs a different (24V) power line and the PS needs a ground. Just cut, run a wire and connect. And of course 2 new 24V light bulbs.
L1&2 and H1&2 represents the head light relays.
Hope this helps a bit.
Good luck
Hi everybody, maybe the pic below can shine a light and be of help for you guys. The top part is the situation as Mr Toyo designed it.
The bottom part is the change to 24V light bulbs. It's pretty simple. There are only two changes to make.
The DS needs a different (24V) power line and the PS needs a ground. Just cut, run a wire and connect. And of course 2 new 24V light bulbs.
L1&2 and H1&2 represents the head light relays.
Hope this helps a bit.
Good luck
Last edited:
Now I understand why it is called "the evil centre tap". Why wouldn't they just draw 12V from each battery?
Nice clean fix there.
- Thread starter
- #31
Unfortunately the wiring seems all messed up on passenger side. My readings from this side headlight are only 12v from the tap wire and no 24v at all. Different colored wires spliced in as well so they don't match up to previous poster with cdn model hj60. Darn it!
If we are asking why's, why didn't they just use 24v headlights when the rest of the system is 24v?
You should be able to find the originals as they are in the same harness branch as the passenger side marker light and passenger side horn and these branch of from the main harness just behind the passenger side battery.
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- #35
kim said:
Yeah I'm exploring this area now. There is some serious melting that happened at some point. There is one wire that went from headlight and is not part of this harness. Some wires have melted together! Yikes this is looking ugly!
- Thread starter
- #36
Don't know if you can see it but looks like a red / green wire was the one that got pooched. Probably a 24v lead.
Something to do with the Cdn DOT or vehicle regulations of the day. This was Toyota's workaround.
jetswim, sounds like you're on the right track now thanks to Kims posts. Follow back to clean, splice in good wire, make sure they show what they should show (confirm that the dimmer relay is indeed working) then hook it all up.
gb
Clean up on isle one!Obviously, with the overheating that has gone on in that harness, you are going to want new wire. IIRC, Toyota lights are relay activated. So does that mean the light switch and high/low switch have 24V at the switch which activate the relays? If so, you could easily directly rewire it to 24V from the relays to the bulb, no? Or, you could just get four 24V Hella relays. 20 amp ones are common at $5-15 each. Run two relays per side (one low bean - the other high beam). Use some 14 gauge wire and you will never melt them again or have dull lights from voltage drop.
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- #39
They are not showing what they should show that is I'm missing 24v.Greg_B said:
Dimmer relay pooched? What does this relay do?
- Thread starter
- #40
kim said:
Photo of 3 headlight headlight wires to passenger side. R/b is 12v, r/w with 2 blue dots is 0v and red one is around 2v but this is the one I think should be 24v.
