Topic: Auto headlights on WJ (Read 9027 times)

gregwho · « **on:** February 04, 2015, 11:02:17 AM »

I've been reading up on wjjeeps.com about the auto headlights which my Grand doesnt have the auto setting on the light switch, but it does have the sensor in the dash board. Does anyone know that if I bought a new multifunction switch with the auto switch, if it would work right off i.e. all the wiring is in place etc, or is there anything else I would need to do to enable it?

Ta!

scrw · « **Reply #1 on:** February 04, 2015, 12:27:29 PM »

reading that info on WJJeeps I am wondering if the BCM needs to be told to enable the auto on function

jay140285 · « **Reply #2 on:** February 04, 2015, 01:03:31 PM »

Quote from: scrw on February 04, 2015, 12:27:29 PM

reading that info on WJJeeps I am wondering if the BCM needs to be told to enable the auto on function

Fairly sure this is the case!

gregwho · « **Reply #3 on:** February 04, 2015, 01:04:43 PM »

Quote from: scrw on February 04, 2015, 12:27:29 PM

reading that info on WJJeeps I am wondering if the BCM needs to be told to enable the auto on function

Is that a dealer only option do you know?

scrw · « **Reply #4 on:** February 04, 2015, 05:03:58 PM »

or someone with a DRB3 tool

gregwho · « **Reply #5 on:** February 04, 2015, 08:18:10 PM »

I don't suppose there's anyone around the southeast who happens to have a DRBIII tool and wouldn't mind me popping over armed with a thank you crate of beer? I'll also give my local dealer a call to see what they would charge to turn it on.

scrw · « **Reply #6 on:** February 04, 2015, 08:19:13 PM »

think Daggie has one

daggie · « **Reply #7 on:** February 05, 2015, 05:50:29 PM »

Indeed I do

however I don't recall seeing this feature

I'll plug it in one or two of our wjs to see if I can find this feature, i'll report back over the weekend

gregwho · « **Reply #8 on:** February 05, 2015, 09:16:27 PM »

Quote from: daggie on February 05, 2015, 05:50:29 PM

I'll plug it in one or two of our wjs

I love that you have more than one WJ!

Thanks for checking this and look forward to hearing what you find. I'm hoping if you don't find anything I can get the multifunction switch and my auto headlights will just work!

daggie · « **Reply #9 on:** February 07, 2015, 05:11:40 PM »

the 99 v8 hasn't got it.
i'll plug it into the 02,4ltr tommorow

gregwho · « **Reply #10 on:** February 07, 2015, 08:43:36 PM »

Quote from: daggie on February 07, 2015, 05:11:40 PM

the 99 v8 hasn't got it.
i'll plug it into the 02,4ltr tommorow

Thank you so much Daggie, really appreciate you checking and owe you a drink sometime!

daggie · « **Reply #11 on:** February 08, 2015, 04:53:16 PM »

Right, the 02 doesn't have it, the sensor is part of the imobiliser/alarm led
1 tried it on a 2000 model, no joy.
the only extras on the drb are
park assit
rain sensor, (the 02 has this)
Tyre pressure monitor.

gregwho · « **Reply #12 on:** February 08, 2015, 06:59:27 PM »

Thanks Daggie, so do you reckon if I get the multifunction switch and plug it in, it'll just work?

Jonny Jeep · « **Reply #13 on:** February 09, 2015, 10:57:11 AM »

Just been looking at the WJ FSM and you should be able to test to see if the auto headlamps will work fairly easily. I don't know if the auto feature should show in the BCM aside from an error code for a missing daylight sensor.

The headlamp switch is resistor multiplexed. Each setting at the headlamp switch will show a different resistance to the BCM which controls the lights. The two relevant wires are white/dark green (headlamp switch return) at pin 4, and yellow (headlamp switch mux) at pin 11. for the auto headlamps to operate the BCM needs to see 74-81 ohms between those two wires.

If you disconnect the headlamp switch and short those wires at the connector with a suitable resistor the headlamps should work on auto if the feature is programmed into the BCM. You may be able to get that resistance using one resistor but may need a couple in series or parallel due to manufacturing tolerances. If the auto feature doesn't work it's cheaper doing it that way than trying a new switch.

gregwho · « **Reply #14 on:** February 09, 2015, 02:08:41 PM »

Quote from: Jonny Jeep on February 09, 2015, 10:57:11 AM

Just been looking at the WJ FSM and you should be able to test to see if the auto headlamps will work fairly easily. I don't know if the auto feature should show in the BCM aside from an error code for a missing daylight sensor.

The headlamp switch is resistor multiplexed. Each setting at the headlamp switch will show a different resistance to the BCM which controls the lights. The two relevant wires are white/dark green (headlamp switch return) at pin 4, and yellow (headlamp switch mux) at pin 11. for the auto headlamps to operate the BCM needs to see 74-81 ohms between those two wires.

If you disconnect the headlamp switch and short those wires at the connector with a suitable resistor the headlamps should work on auto if the feature is programmed into the BCM. You may be able to get that resistance using one resistor but may need a couple in series or parallel due to manufacturing tolerances. If the auto feature doesn't work it's cheaper doing it that way than trying a new switch.

Thanks JJ, thats some great info. To make sure i've got this correct, in layman terms are you saying:

Headlight switch ----> White/Green wire pin ---->Resistor (between 74-81ohms) ----> Yellow wire pin ----> headlights should turn on

I dont have any resistors, is there any other way to put the resistance between the wires? If not, it'll have to be a maplins run and whatever horrific money they charge per resistor!

gregwho · « **Reply #15 on:** February 09, 2015, 02:22:19 PM »

Ok, so I shouldnt have knocked Maplin before I looked it up

prices aren't too bad.

If I get a 68 Ohm (http://www.maplin.co.uk/p/metal-film-06w-68-ohm-resistor-m68r) and a 10 Ohm (http://www.maplin.co.uk/p/metal-film-06w-10-ohm-resistor-m10r) and soldered them together to give me 78Ohms, would that be ok? For the wire I'm going to put on either end to plug into the pins, is there any particular gauge I should use?

Jonny Jeep · « **Reply #16 on:** February 10, 2015, 09:05:01 AM »

78 ohms using those resistors should be fine. They are 1% tolerance so will be 77-79 ohms which is within the range needed. Wire gauge won't matter much for this test so use what you've got. I've just looked at the price of those resistors, I remember when they were 6p each.

You have it down correct for the resistor between the white/green and yellow wires. It'd be nice if it works as you'd get the auto lights by just swapping the switch.

gregwho · « **Reply #17 on:** February 10, 2015, 10:12:06 AM »

Ta again! Glad my basic electronics knowledge is good enough!

I just wanted to check that the plug I need to access to connect the pins is where the multifunction (indicator/lights etc) switch plugs into the wiring loom behind the steering wheel? Just unplug switch and connect pins?

Jonny Jeep · « **Reply #18 on:** February 10, 2015, 10:51:12 AM »

Correct.

gregwho · « **Reply #19 on:** February 12, 2015, 11:59:40 AM »

Success!

So, i made my lovely (and so professional

) two resistor tool (see pictures), managed to get the cowling off the steering rack and found the switch plug. Connected the two pins and headlights turned on, along with a bulb on the dash. I thought that was a bit weird as it looked like the fog lamp indicator. Realised that the plug was upside down compared the the diagram in the FSM, so i'd connected the wrong pins. Swapped the wires over to the right pins, and nothing happened. No headlights turned on. I touched the light sensor (for no reason at all other than to see if it was there) and, lights turned on!! So, i'm wondering if I could have just put a bit of wire between the two pins and that the sensor provides the correct Ohm resistance?

Anyway, my thinking is that if I get the switch, my auto headlights should work....does that sound rational?

scrw · « **Reply #20 on:** February 12, 2015, 01:27:03 PM »

one way to find out......

Jonny Jeep · « **Reply #21 on:** February 12, 2015, 10:54:32 PM »

Looks like a new switch will do the trick.

You can't just short those wires as the body control module looks for different resistance values there to see what lighting option is selected, the electrickery in the BCM then does the rest. I'm not sure what type of light sensor is used, but if it's a simple light dependent resistor, when auto headlamps are selected the BCM will look at the voltage/resistance from the sensor to cross a preset threshold before turning the headlamps on or off.

gregwho · « **Reply #22 on:** February 19, 2015, 12:02:31 PM »

After much searching and emailing, it looks like the WJ's never had the option for auto headlights and both front and rear fogs (mine has both fog options, the switch end pulls out for fronts and then twists for rears). The switches available with auto only have a single pull out option. I was just wondering if anyone thinks that the pull out will combine both front and rears and turn them both on with the single pull out, or if I go for auto headlights, i'll lose my rear fogs?

Jonny Jeep · « **Reply #23 on:** February 19, 2015, 10:19:44 PM »

I shall need to check FSMs to see what's what there. What model year is yours just in case there are differences?

gregwho · « **Reply #24 on:** February 20, 2015, 04:24:40 AM »

Thanks JJ, mines a 2003 (2.7 crd)

Author Topic: Auto headlights on WJ (Read 9027 times)

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