Technical 500X 2015 DRL Failure - Melted Bulb Holder

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Technical 500X 2015 DRL Failure - Melted Bulb Holder

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So my first failure out of warranty. (4 years+) Sadly not just a blown O/S bulb but a melted bulb holder. The holder connector pins to the cable female connected were all OK. Instead the bulb base was welded due to heat into the bulb holder.

Good news is that the holder is available from Fiat at £12 and you don't have to purchase a complete new unit.

I've ordered two new holders and when I come to fit them I'll check the N/S for signs of over heating.

I have some potential theories:

1) Normally 21W bulbs are not 100% duty cycle and used for brake, indicator and periodically rear fog.

2) The other day I left the car idling for 20 to 30 mins so there would have been no air circulation in the inner wing areas.

I'll be checking the N/S DRL for signs of overheating.
 
So my first failure out of warranty. (4 years+) Sadly not just a blown O/S bulb but a melted bulb holder. The holder connector pins to the cable female connected were all OK. Instead the bulb base was welded due to heat into the bulb holder.



Good news is that the holder is available from Fiat at £12 and you don't have to purchase a complete new unit.



I've ordered two new holders and when I come to fit them I'll check the N/S for signs of over heating.



I have some potential theories:



1) Normally 21W bulbs are not 100% duty cycle and used for brake, indicator and periodically rear fog.



2) The other day I left the car idling for 20 to 30 mins so there would have been no air circulation in the inner wing areas.



I'll be checking the N/S DRL for signs of overheating.



I just had to replace both DRLs after about 50k miles, but fortunately there was no mention of damaged bulb holders and both DRLs have performed faultlessly since the change
 
I'll be looking at the N/S today to check for signs of over heating but also to check on the bulb holder design.

I'm unsure as to whether in innards of mine broke on extracting the welded in bulb but once I got the bulb base out there was ONLY one 180 degree bulb side electrical contact strip.

If this is the case then the plastic side wall of the bulb holder that melted was in direct contact with the bulb base side wall and being pressed against it by the 180 degree contact strip in the other side. If this is the case then it is a silly cost reduced design as there is no additional hot spot heat distribution that is provided by the 180 degree metal contact strip like on the other side.

If so the I think I'm going to copper slip the plastic side surfaces (and bulb). This should help distribute heat from any hot spot and if not hopefully stop the bulb base getting stuck to the plastic housing when it does heat up.
 
I'll be looking at the N/S today to check for signs of over heating but also to check on the bulb holder design.

I'm unsure as to whether in innards of mine broke on extracting the welded in bulb but once I got the bulb base out there was ONLY one 180 degree bulb side electrical contact strip.

If this is the case then the plastic side wall of the bulb holder that melted was in direct contact with the bulb base side wall and being pressed against it by the 180 degree contact strip in the other side. If this is the case then it is a silly cost reduced design as there is no additional hot spot heat distribution that is provided by the 180 degree metal contact strip like on the other side.

If so the I think I'm going to copper slip the plastic side surfaces (and bulb). This should help distribute heat from any hot spot and if not hopefully stop the bulb base getting stuck to the plastic housing when it does heat up.

Well N/S checked and no obvious signs of over heating.

I can confirm that the bulb holder ONLY uses a single sided 180 degree semicircle side body contact.

I've now copper slipped both N/S and O/S holders on both the plastic side wall and the contact strip. Will see how we get on.

Whilst on the job I took the opportunity to test a Halfords (off road use only) 382/P21W Super Bright LED Bulb (172449).

The bulb appears to work without triggering a dash board light warning when in normal headlamps off and headlamps on modes.

When the headlamps are turned on the LED bulb does dim but not by much. This is because the driver electronics would appear to be doing their best to keep the constant current flowing.

IMHO it is too bright for day and especially night use (headlamps on).

Was always intending to stick to the normal non LED set-up (one less thing to tell the insurance company about) and now even more so. Just had to try anyway while I was "in there".
 
Probably wise. I did succumb to bending the rules when I had my 500X by fitting an led reversing lamp. They were cheap in the "managers clearance" bin at the time. A worthwhile improvement, but only from "useless" to "fairly pathetic"!
 
Probably wise. I did succumb to bending the rules when I had my 500X by fitting an led reversing lamp. They were cheap in the "managers clearance" bin at the time. A worthwhile improvement, but only from "useless" to "fairly pathetic"!

I did as well. I wrote in another thread in quite some detail about reversing light regulations (or almost lack off) and I could see no show stopper reasons regarding legality. Also told my insurance company I was doing it as the existing set-up was useless and risked accidental vehicle damage on not being able to see anything when reversing in the dark.

https://www.fiatforum.com/500x/450881-500x-drl-led-upgrade-2.html?p=4300370
 
Well I've just done it.

Removed the combo light out of interest, changed the bulb and created a little guide!
 
Last edited:
As per the guide arekp just posted.

However for bulb and holder replacement you do not have to remove the wheel or mess with the wheel arch liner. Just remove the cover flap and reach in.

Grasp the back of the bulb holder and gently turn anti-clockwise.

If the bulb is stuck/welded into the holder then:

1) smash and remove the glass bulb
2) with a pair of wire cutters/tin snips cut the bulb metal casing vertically down as far as you can to the edge of the holder
3) with a pair of long nose pliers grasp the bulb metal casing and then gently twist and roll inwards the metal working your way around

Go gently and the bulb will come out and you should be able to re-use the holder OK.
 
Nearly would have had an MOT failure tomorrow.

Yesterday checked all the lights with the help of the boss. All OK as I was expecting.

Today checking the wipers blades and washer the dash signalled a DRL failure. Grrrrrrr.

As before two+years ago the bulb was black, filament worked OK (once wobbled) and the hold melted as before. Clear overheating.

Decide to fit new bulb anyway and the bonding on the glass envelope to the base failed and the bulb split.

This is clearly a rubbish design.

Have check with my friendly Fiat parts manager and he holds plenty of the bulb holder in stock and has confirmed the original part number of 7736732 has not been changed/superseded so still the original bit of rubbish.
 
replaced both DRL bulb holders today because driver side had melted, was giving intermittent blown bulb error
part number: 0077367320-001
also, new bulbs
20231012_drl.jpg
 
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