Headlights And Ecu

[Vyker]

Hi All

I recently bought a set of HID bulbs and ballasts from an eBay seller.

After alot of mess with getting it all working, I reached a point where I had both bulbs working fine for a week, then the passenger side bulb failing.

Got the bulb replaced, but it now does not work on that side of the car. To reiterate, the bulb and ballast when connected to the driver side Lexus plug, would work fine, connecting it to the passenger side Lexus headlight plug, and it doesn't work any more, also to note, that when I plug my old halogen bulb back in, it works fine, just not the Xenon one.

After looking at the wiring diagrams i got off eBay, it shows that the control switch in the cabin passes through the ECU then to the lamps to switch them on.

I thought I would check, with my volt meter, the power going to each plug and found that the driver side reads 12.04v and the passenger side at 12.01v, a very very marginal difference, which has LED me to believe the following...

Could the bulb that died when it was working, "shock" the ECU into "limp" mode of power to the passenger headlamp bulb by limiting the amount of volts to that side, just enough to prevent my new bulb and ballast from firing up but enough for the older halogen one? would resetting the ECU help? [i'm reluctant to do so as i have no way of retrieving codes on there if any, and i dont want them lost]

Is there anything i can try to get it working? or anyone who has had this kind of problem before?

I know of a relay that you can buy to pick up power directly from the Battery [thanks Wozza] but there are so many others who have a set working that did not need to do so.

Any help would be grand

Thanks

Signing out, a puzzled Vyker

[Geoffers]

You are right in that .3 of a volt is marginal, but if the ballast is regulated, then that can make all the difference at the voltage you have. Usually, a 12v regulator needs 12.5+ to function correctly. Your output there should be 13v+

Was this measurement under load? Would you do it again with it under load from normal bulbs if not and report the readings back? Also, with the engine running and revs quite high and under load.

Although the lights are controlled by the ECU, they go through relays at the final stage. The only ones current controlled directly by the ECU are DRL's - do you have a US version of the diagram?

I would look at a connection issue, bad earth or even a low Battery. You shouldn't lose that much through the resistance of cable at that length. When you rev up, what voltage do you get at both sides - that does seem a bit low for both sides actually. Contacts could be oxidised at the relay.

Putting both hids back in, if you rev up and while your revs are high, switch on - do they light?

[Vyker]

Thats alot to take in there Geoffers, but im grateful for it all.

I'll head back outside and try all that you suggested.

I'll be back in an hour :)

Thanks again

[Vyker]

Back.....

I did as you said, and the volt reading with the engine on and with plenty of revs took it up to 14.33v on the passenger side.

But it still would not fire, to which my dad mentioned "will you just reset the damn ECU!"

I pulled out the 2 fuses, waited 5mins, put them back in again, started it up and it worked! :D

So it seems the ECU was doing something to stop the ballasts from firing, I wish i can tell you what it was that it was doing! :S

The problem i now have is the 2 bulbs are different colours, one is bluey/white, and one is green/white.... This HID mod is endless!

Geoffers, thanks again for your help!

[waynejordan02]

had a similar problem although mine just turned out to being the 10amp fuse blowing as each headlight has its own fuse under the bonnet

[sparkystav]

Glad you got it sorted mate,

but also does the standard wiring power the ballast or power a relay thats directly linked to the Battery to power the ballast?

If its the first version then that could be why as its drawing a much larger current through the ecu than normal.

Stav

[Geoffers]

but also does the standard wiring power the ballast or power a relay thats directly linked to the battery to power the ballast?

I'm confused over this too.

Really glad its sorted though mate.

I'm interested in the cabling. I've not known the ECU control the current to the lamps directly on any UK vehicle. Would you mind dropping over a link to the diagram you have? What happens if you take out the lamp relay? If the ECU is controlling it directly, you would have no need for this.

Also, when you flash your highbeams, do the HIDS flash too?

Its really puzzling this one. Are you getting the same voltages?

[Vyker]

The setup of the unit is as follows...

Lexus plug connects to the bulb, which has 3 further connectors that go directly to the ballast.

So there is never a link between the setup and the Battery.

There are units that you can buy which connect directly to the Battery in instances where there isnt enough power to use Xenons, however, I've not used one in this case.

Geoffers, the lamp relay must still be in use, but is next in line after the ECU, as in, once you flick the switch in the cabin, it passes through the ECU, then to the relay, then into the bulbs.

Could it be that the ECU would only pass a small enough current to the relay to prevent it from providing full power to the bulbs?

I will try to find a way of getting the diagram my father saw over to you, but it might prove difficult as he saw it in passing and its in a huge single PDF document.

I'm not sure about the flash question, i will try and get some one to come out with me tomorrow night to check to see if the HID's flash with the highbeams.

[sparkystav]

The high beams are a different bulb so the HID's wont flash.

See my setup works by, when the lights turn on, that operates a relay (part of the HID kit), that in turns links the Battery directly to the ballast to start it up.

Stav

[Vyker]

Also, when you flash your highbeams, do the HIDS flash too?

The high beams are a different bulb so the HID's wont flash.

checked this last night, and no, they dont flash with the highbeams.

Ill work on getting you the diagrams, it is an odd one this.

I personally never thought the ECU did as much as even this little problem!

I knew cars are becoming more complex... but this is just Windows! [iT Joke :P ]