DRL bulb failure

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Papa Bear
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DRL bulb failure

Post by Papa Bear » Mon Jul 27, 2020 8:48 pm

A few weeks ago I had the dash warning saying a bulb was out, was a DRL.
Replaced both with these
https://www.ebay.co.uk/itm/283047985879
2 days ago I got the warning again, checked and one bulb blown. Tried swapping bulbs side to side and holder to holder but the fault followed the bulb. Filaments look fine and work on sidelight. Contacted seller and they asked for a photo of th3 bulb so just been to take it out and now both aren’t working. Checked with a multimeter on the bulbs and they have continuity so maybe not blown. I’ll try them in the rear tomorrow but hoping one of you geniuses might have an idea what’s going on
Please :D
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Giddy
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Re: DRL bulb failure

Post by Giddy » Mon Jul 27, 2020 9:50 pm

If they are connecting to the contacts inside the sockets ok, then perhaps something to do with the bulb resistance. Maybe it's too low and the BCM shut the output off to prevent itself from blowing up.
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Papa Bear
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Re: DRL bulb failure

Post by Papa Bear » Mon Jul 27, 2020 9:58 pm

Cheers @Giddy, Could that happen on normal bulbs as opposed to leds?
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Giddy
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Re: DRL bulb failure

Post by Giddy » Mon Jul 27, 2020 10:06 pm

Yes, I've seen bulbs like this. They visually look ok and have continuity when measured, but do not light up.
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Papa Bear
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Re: DRL bulb failure

Post by Papa Bear » Mon Jul 27, 2020 10:08 pm

Ok thanks, off to Halfords in the morning to pick up some bog standard ones
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Stedlocks
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Re: DRL bulb failure

Post by Stedlocks » Mon Jul 27, 2020 11:01 pm

Sometimes if you spin em 180° they work?

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Papa Bear
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Re: DRL bulb failure

Post by Papa Bear » Mon Jul 27, 2020 11:12 pm

Offset bayonet, won’t fit the other way round, tried it :D
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Re: DRL bulb failure

Post by Stedlocks » Tue Jul 28, 2020 1:01 am

Ah...!
:D

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C Chis
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DRL bulb failure

Post by C Chis » Tue Jul 28, 2020 6:46 am

Hi [mention]Papa Bear [/mention]

A quick check on the resistance of the bulbs might help.

Assuming a 12 volt, 21w/5w lamp

Power = Volts*Amps
21w = 1.75 Amps
5w = 0.42 Amps

Resistance (Ohms) = Volts/Amps

21w = 6.8 Ohms
5w = 28.6 Ohms

So, you should be getting approximately the above resistance values across the filament between the +ve pin and the outer -ve metal casing

Short your multimeter leads together before taking the lamp readings and if it doesn’t read zero add the value on the display to any readings you take across the bulbs

Note: avoid touching the probe ends with your bare hands in case your multimeter range is on high or you can get false readings due to the resistance of your body


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Papa Bear
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Re: DRL bulb failure

Post by Papa Bear » Tue Jul 28, 2020 6:18 pm

Twin filament bulbs so first bulb
Between outside and one terminal about 6 ohms
Between outside and second terminal about 640 ohms
Between the bottom terminals about 700 ohms

Second bulb
Between outside and one terminal about 4 ohms
Between outside and second terminal about 1100 ohms
Between the bottom terminals about 1100 ohms

eBay seller says “I tend to hear back from customers about the caddy's having problems“
Have offered replacement but as one bulb didn’t work when they arrived and had that replaced already I’m thinking these are not a good purchase
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Re: DRL bulb failure

Post by C Chis » Tue Jul 28, 2020 7:09 pm

Yip, dud’s!

Most likely a crack in the sealing compound letting water in and causing resistance issues.

The resistance between the 2 bottom terminals should be the sum of both the readings as your circuit is made from terminal 1 through the filament to the casing and back through filament 2 to terminal 2.

I’d be sending them back asking for a full refund and try another manufacturer

Most other vehicles without the active error checking wouldn’t show any faults other than perhaps a dim bulb until the moisture had been driven off with the heat of the bulb.


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Papa Bear
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Re: DRL bulb failure

Post by Papa Bear » Tue Jul 28, 2020 7:39 pm

Thanks mate, asking for a refund now. Must find the post on here that recommended them and leave a comment :D
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Papa Bear
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Re: DRL bulb failure

Post by Papa Bear » Tue Jul 28, 2020 11:20 pm

Seller has come back with
“Hi the ohms on bulbs must be tested with running 12v through them

Many try to test resistance without any power and that is not correct for the bulbs”
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C Chis
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Re: DRL bulb failure

Post by C Chis » Wed Jul 29, 2020 7:46 am

Sellers talking rubbish!,

You can measure the voltage and the current of a live circuit and use those figures to calculate the resistance (Ohm's Law) by using the calculations in the previous posts, however you can't actually measure the resistance of a live circuit as the voltage will interfere with the reading (simple answer).

If they’re not willing to refund, I’d be putting in a claim via PayPal.


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Papa Bear
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Re: DRL bulb failure

Post by Papa Bear » Wed Jul 29, 2020 8:10 am

Pretty much what I said to them. It’s a shame I already left positive feedback
Waiting for reply from them
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