Strange electrical issue

[ta240]

Hi, I have a 2012 Mazda3 with the 2.5l engine.

We were driving along for about 15 minutes and the interior light suddenly turned on and then faded out like it does when you shut off the car and get out. About 10 minutes later we slowed down in traffic to nearly a stop and as we accelerated the door locks cycled like they do for the automatic locking when we hit 5 mph; but that had happened already quite some time ago.

I have added daytime running lights that just connect to the battery and sense when the car is running to turn on; they have been on it for over 5 years. One of the things they have always done is when we turn the car off and exit they shut off and then as the relays in the engine click off they turn on for a half a second before staying off; apparently the switching of the relays makes them think the car is running.
We got to our destination, parked and about 5 minutes later we were walking back to the car and we saw that the daytime running lights were cycling on and off as though something was switching on and off in the car and triggering them to think the car was running.

Due to where I tap in for power for the DRLs I can confirm that the ETV fuse under the hood was getting power with the car off and it shouldn't.

Any ideas what to check?

 

[concept]

The first thing I would do is look for a loose connection - either connector or ground. A thorough visual is in order.

 

[ta240]

excellent idea. I'll check all the connections and clean the grounds. I pulled and reinserted all the relays in the fuse box. All the connections on those were clean.

 

[Gus75]

Hi, I have a 2012 Mazda3 with the 2.5l engine.

We were driving along for about 15 minutes and the interior light suddenly turned on and then faded out like it does when you shut off the car and get out. About 10 minutes later we slowed down in traffic to nearly a stop and as we accelerated the door locks cycled like they do for the automatic locking when we hit 5 mph; but that had happened already quite some time ago.

I have added daytime running lights that just connect to the battery and sense when the car is running to turn on; they have been on it for over 5 years. One of the things they have always done is when we turn the car off and exit they shut off and then as the relays in the engine click off they turn on for a half a second before staying off; apparently the switching of the relays makes them think the car is running.
We got to our destination, parked and about 5 minutes later we were walking back to the car and we saw that the daytime running lights were cycling on and off as though something was switching on and off in the car and triggering them to think the car was running.

Due to where I tap in for power for the DRLs I can confirm that the ETV fuse under the hood was getting power with the car off and it shouldn't.

Any ideas what to check?

My son upgraded his Toyota Corolla lights to LED's and paid a handsome buck for no doubt Chinese LED kit from some online site. Then he called me with problems with his lights and wiring getting HOT. This add on junk for lights if not well made or installed correctly will BURN your wires in places you cannot access or see! On newer cars, best not to mess with the electronics. Anyway, to cut a long story short, i told him to take it all out. And he was fine after that. If there is an IMBALANCE in electrical load, ie can occur if one light bulb burns out and load increases on the other opposite bulb, thus causing weird problems until burnt bulbs changed. I have had this troubling is on GM cars as well, and dealer fixed it by just changing both headlight bulbs. I tested everything and all looked good, but dealer told me that this is the type of problem you get from something so simple. Always replace bulbs in sets, even if only one is burnt. The filament gets thinner as bulb gets older and that changes resistance in total circuit.

 

[negusm]

Did you calculate your DRL load to the new circuit and verify the relays and the power feed are within spec? As was noted, aftermarket electronics wreck havoc on modern cars. Circuits are spec'ed at the factory and built for specific current loads.

Regardless, these DRLs appear to be failing and I wouldn't trust them. Remove them. See if the problems correct themselves.