Stereo losing power completely when switching ignition off

M

Martynt74

Member
Supporting Member
Joined
Apr 13, 2023
Messages
73
Location
Spain
I bought my TJ with a Kenwood aftermarket stereo, it always reset with the ignition, and so never stored any data for the clock/settings etc which was annoying. It was also horrifically flashy.

I bought a Blaupunkt Madrid 200 which looks a little more muted. The wiring harness was already fine and so i connected it all up and it works fine. However the same thing happens where the stereo loses all memory with the ignition.

I've read a few things regarding the yellow wire needing to be switched, but i'm not 100% sure what i need to do here.

It's worth noting that the car was modded with a 12v cut off box which has a key that when turned will disconnect the battery completely. However i rarely (if ever) actually use that.
 
  • Like
Reactions: Jerry Bransford
Car radios need 3 power wires... a ground wire, a constantly live +12 v, and a switched +12 volt that turns the display and radio off & on. The constantly live +12 lead keeps the clock and the station presets alive.

From your '98 TJ's radio wiring harness its colors are:
Constant +12 volts is a pink wire with a white tracer running down the pink.
Switched +12 volts is a solid pink wire.

The radio gets grounded through its mount plus usually a braided ground strap that connects to a bolt on the back of the radio.

Here's a wiring schematic...

Radio.JPG
 
  • Like
Reactions: Rut Row, CreepinDeth, Apparition and 1 other person
Brilliant.

Thanks both. I also have a weird issue where the Bluetooth makes a screeching sound, but only occasionally and cycling the ignition often fixes it.

The weird thing is that the FM radio/aux input work fine at all times so that’s an odd one!
 
Martynt74 said:
Brilliant.

Bluetooth makes a screeching sound, but only occasionally and cycling the ignition often fixes it.
Click to expand...

Both radios?

Cheap unshielded spark plug wires can cause radio interference.

So can bad grounds. The factory radio is grounded with a braided flat copper cable to a spot under the gauge cluster.

-Mac
 
macleanflood said:
Both radios?

Cheap unshielded spark plug wires can cause radio interference.

So can bad grounds. The factory radio is grounded with a braided flat copper cable to a spot under the gauge cluster.

-Mac
Click to expand...

The first didn’t have Bluetooth which was a big part of replacing it.

I’ll look to improve grounding. There’s certainly no braided cable in there anymore.

It’s been sat a few months and whilst mechanically it’s been fine since starting it back up and done around 1500 miles in a month the electrical side has been dodgy.

1. Had the rev counter and Speedo drop to zero
2. Battery spiked to 20v before dropping back to normal
3. Randomly lose the lighting to the dash

They all seem to come back on after a while which suggests a bad connection.
I have been pulling out a few aftermarket devices spliced into the 12v rail so every chance I’ve knocked something!
 
The volt meter spiking to 20 volts is likely nothing more than a bad connection at the battery since the volt meter is actually measuring the voltage out of the alternator. The alternator will keep raising its output voltage if it doesn't see a good 12 volts from the battery. Remove both battery connections then use a wire brush or a wire battery brush to clean both the battery posts and the inside of the connections. Then securely reinstall both battery connectors, tightly enough that you can't move either with even considerable hand pressure.

This type of battery brush works well, it includes both a male and female wire brush which makes this job quick and easy.

battery brush.jpg
 
  • Like
Reactions: CreepinDeth and tr21triton
Or…there is a parasitic draw larger then they considered acceptable in the deck and it killed their battery. So they removed the 12+ constant

So if you decide to hook it up correctly, be sure to check the parastic draw on that circuit afterwards

Typically, the normal amount of parasitic draw is between 50 and 85 milliamps in newer cars and less than 50 milliamps for older cars.” A parasitic draw above this threshold is considered excessive. Over time, excessive drain can stress your battery, drawing it down quicker and shortening its life.
Click to expand...
 
CreepinDeth said:
Or…there is a parasitic draw larger then they considered acceptable in the deck and it killed their battery. So they removed the 12+ constant

So if you decide to hook it up correctly, be sure to check the parastic draw on that circuit afterwards
Click to expand...
Even the PCM places a constant draw on the battery. It's smarter to just keep a battery maintainer on the battery if it's not going to be driven enough to keep the battery charged.

This is what stays permanently connected to my battery, its AC cord is accessible through the grill for easy access to plug it in for when I won't be driving it. I have it mounted permanently to the top of the air filter box. https://www.amazon.com/gp/product/B0000AXTUY/?tag=wranglerorg-20
 
  • Like
Reactions: macleanflood
Yes, hence the language “larger then they considered acceptable”. Obviously anything that holds settings has a parasitic draw, and u need to ensure its within range

Meaning, its defective to a degree and pullin more load then it should. This is a common issue people troubleshoot and realize their stereo has a short somewhere constantly pullin more load then it should while off

Thats why I told the OP to check the parasitic load to confirm its in the acceptable range if he hooks it up to eliminate that possibility for it being left disco’d
 
Top Bottom
Back