Braking kills your head unit? How not to be slow to the draw like me.

BLUF: having electrical gremlins? Get a battery test instead of wondering what the heck is going on but not doing anything more than your own diagnostics and unplugging stuff.


Wall of text follows.

So...I installed a new dashcam with a hardwire option to grant parking mode after the truck is off. This sources from the battery until it reaches a specified voltage. My unit adjusts from 11.8 to 12.4V in 0.2V increments.

Shortly after, I noticed my head unit would completely power off, then immediately power on, right after braking. I have an OR model which has an electronically assisted brake pump. My leading theory was using the pump was putting load on the electrical system such that the voltage and/or amperage reaching the head unit was too low.

My problem was, I could not get this weird reboot to reliably occur. It tended to happen most often when the battery was likely on the lower side with regards to voltage, i.e. I hadn't driven it recently and/or very far. However, even then I still couldn't get this issue to reliably occur. I unplugged the dashcam, auxiliary switches and stuff, and still would sometimes have the issue, sometimes not.

Well, I was on the road for a few hours, stopped to fuel up, then got back out there. I braked while turning onto an on ramp and the reboot occurred. "No big deal", I thought, as this has happened before (narrator: "It was a big deal"). But as I accelerated, my entire electrical system must've been salty, because the MFD, all dash lights, and all guages kept fluctuating between power states. Truck seemed to be fine but I wasn't taking that chance. I immediately pulled over to diagnose but couldn't get anything to reproduce so cautiously went on my way.

Never had an issue again until yesterday when I went to start er up and it was hella ded. Jump started myself then drove to an Autozone for a battery test. It immediately failed the test. For reference, it's a 4+ year old OEM 24F battery. I knew it was on its way out, but having never witnessed this kind of electrical malfunction before, and given the fact that the vehicle was otherwise fine and started without fail (with this occurrence being the sole exception) I thought it was something I did. Replaced it with a Durolast platinum 24F and drove around. No issues. Connected everything back up the next day and drove around. No issues. Also worth noting, a voltmeter I have in the bed was measuring ~12V (11.8V was the lowest I saw) with the OEM battery. Measures 12.7V now (both measurements when truck was off).

Anyway, all this to say, get your battery tested if you're having weird gremlins like that. It's free. Would've saved me some heartache. Another tool added to be troubleshooting toolbox, as an old instructor used to say.

 

Is your new battery an AGM?

If so you need a charging voltage booster.

 

It is not. I was already researching a replacement but given the spontaneity of this scenario, opted to go the simple route. I will be upgrading to a dual battery setup down the road and will likely go AGM (and get a tune to up the voltage).

 

https://www.tacomaworld.com/threads/braking-causes-electrical-issues-radio-shuts-off-solved.684475/

 

Well I'll be damned. I didn't do a thorough search before posting so that's on me. But I seldom miss a chance to declare my dumbassery.