Fiat 500 Forum banner

Interior light fuse blowing

42K views 42 replies 22 participants last post by  yaygull 
#1 ·
THe other day my overhead lights stopped working, so today I change the fuse. With the car off, I put the new fuse in and immediately it sparks and blows the fuse. I went through 5 fuses. Has anyone seen this before? The thing that really sucks is that I just hit 50k, so no more warranty.
 
#2 ·
I have not heard of this issue until now, did you upgrade to the LED interior lights or make any other changes that could affect it? I haven't checked but what else is tied in with the interior lights (if anything). I can look it up if needed but I assume you have at this point during your troubleshooting process.
 
#5 ·
Certainly sounds like a fault or short somewhere, hopefully no other portions of the electrical system begin to suffer the same fate. I understand you are out of warranty but it wouldn't hurt to at least talk with the service department and see what (if anything) they'll say that might be useful. Really depends on the relationship you have with your dealer though how that plays out.
 
#7 ·
I can't recall if anything exists in the doors or hatch that are in the int. lighting circuit, but one common place for shorts in vehicles is in the wiring loom going to doors/hatches. In extreme cold the wire and insulation can become brittle and crack during the bending taking place as the door is opened/closed. Manipulating the looms at those points might lead you to the short. A short finder is easy to make and use. It consists of a small flasher relay and wire and clips, along with a compass. You hook up the flasher relay in circuit at the fuse location, and follow along the wiring path with the compass. Flasher sending intermittent current makes the needle oscillate. When the needle stops and points solid, due to the magnetic field set up at the short to ground, you've narrowed down the location and just need to examine that bit of wiring. I seem to recall hearing of someone with a short in the loom leading from the body to the hatch door.

I hope that helps some. Sears has a short finder listed. I purchased what I think was a Lisle brand short finder at Pep Boys.
 
#8 · (Edited)
I explained it wrong at one point above, sorry. The compass will oscillate due to the magnetic field pulsing through the wiring, as you travel out from the power source. When the needle stops oscillating, you've passed the point of the short to ground. At the point you lost the signal is near where the short is.

i also mistakenly called it flasher relay. You want a five amp resetting circuit breaker
 
#12 ·
I have come across this problem before and it is only on the early build 2012 500 with the oil viscosity sensor in the oil-pan. The sensor is shorted but is not used by the p.c.m. anymore so no codes are set. Raise the vehicle, remove lower shield & cut the red/orange wire on the 3-wire connector of the oil-visc sensor on the passenger front corner of the oil-pan. This will remove the short from the light circuit, not cause any problems and fix the blown fuse problem.
 
#15 ·
Just bought a 500 C and we are having this same issue. This post caught my eye in particular because when we had our mechanic inspect this, he commented on the "new" sensor in the oil pan.

I wonder if the place I bought this car from saw the cut wire and replaced the sensor....

However, I can't find any other link online that offers this same cause/solution (maybe my powers of Google-fu are weak today...)

Can anyone confirm this oil sensor issue as being related to the interior lights fuse?

This car is a 2012.

Thanks.
 
#18 ·
Hi bryanintowson,
It would depend on the type of extended warranty you have and the cause of the issue. I'd be happy to look into this if you'd like!
 
#20 ·
This ended up being a multi-faceted issue for me.

The oil viscosity sensor was indeed blown and causing a short. This was replaced - and the BCM was replaced as it showed up bad on a diagnostic run by my studio. They also discovered a leak in the rubber boot that covers the wires that go into the hatch that also caused them discover a frayed wire in that bundle. They sealed up everything, mended the wire and put everything back and so far so good. Another symptom that showed up was my dome lights going out and not working.
 
#30 ·
I can confirm that cutting the red wire solves this issue and doesn't seem to harm anything. My wife's 500 Sport kept blowing fuses for the dome light immediately, so I took the advice I found in this thread (plus in a related thread elsewhere talking about why the oil viscosity sensor is no longer used) and cut the red wire.

I was just going to pull the sensor and disconnect it, but I couldn't get the thing free, even when prying with a screwdriver while pushing on the little tab. When I opened up the wire protection sleeve, I found that the red and purple-ish wires had somewhat melted together and created a short. At first, separating the wires allowed me to put in a 5-amp fuse without blowing it, but as soon as I buttoned everything up and lowered the car, I noticed that the dome light had stopped working. (Hopefully this saves someone else a headache later!) I went ahead and cut the red wire, wrapped both ends in electrical tape, and put it all back in the plastic sleeve. We drove the car around this evening with no engine problems, and the dome light continued to work.

I'm attaching a picture of the snipped wire as proof for anyone worried about cutting it, and for future reference in case anyone needs another view. Hope this helps someone like you guys have helped me!
 

Attachments

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top