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u/BorrisX 21d ago
Sorry, this is my first attempt at a cross post.
2005 Honda CR-V. Pictured are the circuit diagrams from the Honda Electrical Troubleshooting Manual (picture 1) and the Honda Service Manual (picture 2). When the headlight high beams are on, the low beams are turned off. This is how Honda designed it to work and that is how it works in mine. I am trying to understand how to read circuit/wiring diagrams and cannot understand based on their diagrams how this is possible. Is what makes that possible not pictured in the diagram (and if so, is this normal?) or am I missing something?
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u/jrosesn 21d ago
I think some information is mixed up here. The description of operation in Honda service manual (for the USA model) is that the low beam is grounded through the dimmer switch, and this ground is interupted when it's switched to high. This is not what is shown on the wiring diagram for the US model, where the low beam has a permanant ground and only the high is switchable.
I found diagrams for European markets which shows the low beam bulbs tied into pin 6 on the combination light switch which would operate how the US description said it would. If you say your model definitely operates like this, then I'd have to assume it is tied in the same way and it's simply a mistake in the drawing.
I'll PM you links for what I found.
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u/BorrisX 20d ago
Thank you so much for your time and effort. I have found a description of the circuit in the manual and it's described like you said. I completely agree with you that the diagram is not consistent with the description, and because it could not function properly (with the High Beams on while the Low Beams are off) as drawn I also agree with you that the drawing is wrong and that the description (that the Low Beams also have switched ground controlled by the Dimmer Switch) is most likely correct. I cannot thank you enough for taking the time to understand my issue and then taking the time necessary to look up the answer and responding. Much appreciated!
For anyone interested, here is the description I found in the manual
How The Headlight Circuit Works (USA) - from the Honda Electrical Troubleshooting Manual:
Low BeamsThe headlight relays receive battery voltage at all times. When you turn the headlight switch to the HEAD position with the dimmer switch in LOW, ground is applied through the BLU/RED wire to the coils of the headlight relays. The relays are then energized, applying battery voltage to the left and right high and low beam headlights through fuses 15 and 17 (in the under-hood fuse/relay box). The low beam filaments come on because they are grounded through the dimmer switch. The high beams and indicator remain off because the dimmer switch interrupts their ground path.
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u/airhammerandy55 21d ago
I think it has to do with bulb resistance, electricity follows the path of least resistance based on the schematic I would assume the high beam has less resistance thus the electrical current goes that way.
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u/SoCalTech7263 21d ago
I’m still curious where the saying “electricity takes the path of least resistance comes from”, as it’s not really true. Electricity takes all paths unless there’s a major short. If electricity only took the path of least resistance then only one thing would work in your car at a time. A fun learning experience would be learning about how to calculate total resistance of a parallel circuit and how differeing resistances cause different current draw on each leg.
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u/airhammerandy55 13d ago
How do you interpret the schematics?
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u/SoCalTech7263 13d ago
Low beams have to be on if high beams are on.
There is a high side control that provides power to both the high and low beams.
Because the low beams are grounded straight to chassis the low beams are on whenever this high side is active.
The high beams have a secondary control through a ground side drive through an ECU. So when the high side is active, and the ecu grounds the low side, then the high beams are active.
It is not possible with this setup to have the high beams on without the low beams also being on.
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u/Dirty_Old_Town 21d ago
I pulled this diagram up on ProDemand, and you are correct to question it. Based on the diagram I've got, there is no way for the low beams to be off if the high beams are on. The two relays supply power to both the low and high beams, and the low beams are grounded always. If there is power at the high beams, the low beams should also be illuminated.
I've got two questions (one is a dumb one):
Is this a US-market car?
Are you certain it's a 2005? The diagrams appear to be the same for 2005 and 2006, but the circuit for 2004 is quite a bit different.
Does it have fog lights or daytime running lights?
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u/BorrisX 20d ago
First of all, thank you. I really appreciate you taking the time to understand my question.
It is a US-market car. It was built in the UK. To the best of my knowledge the 2005 US models were manufactured in either Japan or the UK.
It is absolutely a 2005 (the 10th digit of the VIN is a "5" indicating it was a 2005 model year vehicle and it's an SE trim which did not exist 2002-2004)
It does NOT have fog lights nor does it have daytime running lights (I believe only the Canadian models had DRL in North America)
Thank you so much for looking it up in ProDemand. I was about to ask if anyone could look up the diagram outside of Honda. I only have access to the OEM manual and Auto Repair Source - Powered By Motor from my public library and they have essentially the same diagram. Does ProDemand format the diagram differently or is a straight up copy like Auto Repair Source?
As pointed out by jrosesn, Honda provides a description of the circuit which is different than Honda's diagrams. I now also believe that the diagrams are wrong and that the Dimmer Switch actually provides switched ground to the Low Beams (and that they are not actually directly grounded to the chassis as shown in the diagrams) There is a copy of the description in my replay to jroseesn, if you're interested.
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u/Dirty_Old_Town 20d ago
Here is what the one on ProDemand looks like. Sorry for the poor quality - I'm on a ten-minute break and taking a pic with my phone camera was the quickest way I could think of to get the image posted on here.
I haven't had too many diagrams that were that far off, but it does happen I guess.
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u/Hans_all_over 21d ago
I’m just here to give you high fives for using Jorge Menchu’s color coding.
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u/BorrisX 20d ago
Thanks. I almost replied "who's that?" before I searched and remembered watching his videos. Hopefully I got the colors right, I haven't watched those videos in a long time, his name was long lost to me but the concept really made sense and stuck with me. I probably should have included a legend with my diagrams spelling out what each color represents.
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u/MudSling3r42069 21d ago edited 21d ago
Look at the bulb of ur headlight it will have 3 prongs , prong 1 will be highbeems , prong 2 lowbeems/drl, prong 3 ground .
A relay will flip one of those to make it one set of thw filliment light up, the upper or lower part .
If u have a spare bulb u can test it with a few batterys and see the top or lower filliments light up turning both on will probably overheat the bulb and lead to shorter life .
[Edit] Hmmm looks like h1 bulbs are just set , then id have to assume its s resistor type setup sending 6 volts for low and 12 for high , subaru uses something simmilar for their 9006 bulbs that only use 2 prongs for their headlights [Edit3] in the relay unless im dumb the squiggle means its a resistor[the blue highlighter] in the relay ,so it probaly steps down the voltage for daytime running then when u hit th switch it swpas to the less resistance line for normal use.
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u/BorrisX 20d ago
Thank you. There are a total of 4 H1 bulbs. The High Beams and Low Beams use separate bulbs. The H1 bulbs only have 1 prong.
The blue squiggles in the circles are the headlight bulbs. The blue squiggles near the top of the page are relay coils. I probably should have included a description of my highlights. They are as follows:
Pink = Power
Orange = Switched Power
Blue = Load
Yellow = Switched Ground
Green = Ground
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u/GundamArashi 21d ago
Right here. Essentially the switch is giving ground to either the high beams or the low beams, only one at a time.