Friend wants to take out my headlight relay and try it on his broken headlight

You have the power over your own destiny. If you feel like this is a bad idea, then it's a bad idea. Stick with what you want, be firm.

Anything can go wrong when you disassemble things. Nothing is 100% harmless and safe. You can strip bolts/screws putting things back together. Anything can happen.

Why not have him buy a new one and put it on? If it still doesn't work, he has 30 days to return it.

 

Your friend needs to check the fuse which supplies power to the right headlight. The relay is not at fault; if it were then the left headlight also would be inoperative.

If the fuse is good then trace 12V to the headlight ballast. If the voltage is good at the ballast, and the HID bulb is known to be good, then the headlight ballast is at fault, as it is not providing a reliable high voltage source to the bulb.

In general there would be no problem in swapping relays; assuming a reasonable repair technique. If your friend guarantees to repair any damage he causes to your car then I suppose you might allow some reasonable swapping depending upon how good of a friend you wish to be. However the relay is definitely not the problem, given your description of the issue.

Usually parts sales will refuse the return of electrical parts to prevent people from doing as you suggest.

 

MacMaster05 – IMHO, a friend asking you to “Cannibalize” parts and pieces from YOUR electrical system to troubleshoot THEIR car is too much for a friend to ask. You may well end up with a “Fried” MacMaster05 headlight relay or lighting system.

Read and heed JC91006’s “Anything can go wrong when you disassemble things. Nothing is 100% harmless and safe” caution, and have your friend follow Patrick Wong’s DIY troubleshooting advice for resolving your friend’s “Popeye Eye” headlight problem with the car’s HID lighting system.

 

Basically testing relay is very low risk thing. But in this topic we already know that it’s not the problem. So before your friend does tests like that he has to know more. Basically you should know every possible way part can fail when doing this and what can break in disassembly and reassembly.

I have twice done test by taking parts off my friend’s cars but those were cars that I did all the maintenance anyway.

 

Can I be your friend?

 

After checking the circuit diagram "for some reason I cannot load" If one headlamp works the relays cannot be at fault. The headlamps however are fused separately. This confirms Patrick's words.

The bulbs can be changed without removing the bumper. Admittedly there is not much room. I have large hands, and I can change the bulbs. The only thing that needs to be removed is the air intake snorkel.

John (Britprius)

 

Yes but a bit too long way to just go hang out together. Or it would be pretty expensive repair work even if you only paid me my trip to there. But if you ever get here I can show you around.

 

This is truly a test of friendship. Yes it's probably not going to cause any damage but if it does come down to something going wrong, this could ruin your friendship if the friend refuses to fix a problem. I don't like to get myself into situations like this.

It's almost like lending friends money, the answer is should always be "NO". True friends will give the friend "in need" money and not expect anything in return. Because if you expect the money to be returned, then most likely the friendship will be lost when the "in need" friend has no money to pay back.

 

There is little risk in doing this, but it definitely is not the problem.
The HID bulbs when failing will usually light when first turned on but after a time "could be up to 30 minutes" will go out. Turning the lights off and back on will bring it back on. This could be why the bulb appeared to work when moved.
Disconnecting the ballast and checking for a 12 volt supply at the cable connector with the car in ready and lights turned on will prove if it is supply failure (fuse, broken wire, or poor grounding).
Check the fuses with a meter not by site marked Headlamp LO left hand and LO right hand. These are the fuse that feed the two ballasts.

John (Britprius)

 

If your friend doesn't know how to check fuses, you really don't want him messing around with your car.