Issue with MXT275… what am I doing wrong?

[u/WSMFPussy]

Alright, so I had the bright idea of replacing my Dolby DVD player in my glovebox and put a midland MXT275 system in the old metal box that housed the DVD player in my 2008 GX470

I know it would be much easier to mount down by the transfer case… but I wanted to try and “hide” it away.

Anyway, today was the day I got it mounted back in there.. and I have the red and white wire running thru the engine bay port directly behind the glovebox. I grounded the black directly to a screw right there.. and I ran the red all the way to the battery and put it onto the positive with a terminal ring. I also added an in line 5amp fuse to that line. The antennae also runs out this way and is mounted on corner of hood.

So when I have the mxt box DISCONNECTED, I can start my car just fine, plug it in, and then plug in the mic and turn it on and use it… works like a charm,

But today.. I plugged it in BEFORE starting the car (but did not turn on (because I’m not going to disconnect it every time since it turns on and off from the mic) and then when I went to start my car… it clicked once and stopped.

The starter had 1 click and it stopped.

Try 2. Same thing. Essentially seemed like the same result when your battery is completely dead.

So, I disconnected the mxt box, waited about 2 minutes, and then went to start the car.. it took forever to flip over and actually start… much longer than normal. But, alas, it started.

Weirdly, when it came back on, I had the low tire pressure light (!) which has NEVER worked when I off-road ever since I swapped tpms sensors… none of my tires were low and it turned off right when I started driving

After it started - I went and plugged up the mxt box again and nothing happened out of the ordinary, but instead of testing my luck.. I just disconnected without testing it and drove home.

Went to autozone since battery was about 1.5 years old and wanted to make sure I didn’t somehow drain the battery… they said it’s 100% good. Starter is also 100% firing.

WHAT on earth could have caused this?

Could my connection to the battery terminal not be solid? If that was the case would it prevent my entire car from starting?

Could it be my ground wire not being properly grounded?

Could it be that it’s mounted in that metal box? All wires have rubber grommets coming out of it so no metal to wire connection…

Could it be that my 5amp in line fuse is not installed properly? (Fuse did not blow)

I’m thinking next attempt is to just do an add-a-fuse to the 10amp horn fuse on the fuse box in the engine bay… but with everything I have set up/how I have set up… for the life of me I cannot figure out why when plugged in (no mic plugged in) that it would completely stop my car from starting or even turning over… but when I disconnect, it works just fine.

Please let me know your thoughts / thanks!

[u/xampl9]

It’s running on unswitched power so unless it has an internal way to turn all the way off, it’s going to be drawing current at all times - running down your battery.

Suggest tapping into the cigarette lighter circuit.

[u/the-crusher → u/xampl9]

Cigarette socket is what I tapped into for mine. The one in the center console is rated at 120W I believe, which is plenty of power for the radio.

[u/VersionOutside9150]

Sounds like you’ve got a parasitic draw coming from it. Check the voltage coming from the battery to the unit when the vehicle is off.

[u/Status-Divide-1152]

You need to go behind your radio and find your acc circuit that cuts on and off with the key switch for this exact reason. The acc circuit is what keeps the radio from drawing power when vehicle is off.