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MG MGA - Radio drains battery?????

I installed a radio and 4 speakers in my MGA 2-3 weeks ago and I've noticed the starter "slowing." Today the car started, drove to the store, but would not start for the ride home. Luckily good Samaritans were more than willing to help me jump start the car.

I have 3 theories:

1. The radio draws power from the battery while the car is not running to retain the programmed channels. But... the radio only turns on when the ignition key is turned on...just like the fuel pump. So how can the radio draw power? And yet the radio channels do remain programmed. hmmm...

2. If I am playing the radio while I drive then there is less power from the alternator to recharge the battery. So over time the battery drains. hmmm... doesn't really seem that plausible.

3. As I began to charge the battery I noticed the cells were low on water... quite low actually. The reduces water is the reason for the slowly dying battery.

Unless there is a definitive answer I'll recharge the battery and observe more closely.
gerard hutchinson

I would say nothing to do with the radio unless you left it blaring while you were in the store for half the morning! Either a poor connection in the battery leads or a dying battery would be my first port of call.

Often I have traced the cause of an apparent bad battery/bad starter motor to the connection between cable and clamp at the battery. Found this now on three different cars with twin 6 volt batteries! Removing the terminal connectors, cleaning everything up and refitting solved the problem. Also found similar symptoms with a loose connector at the starter motor.
Neil MG

If the "water" level in the cells is below the top of the cells the battery will not provide the cranking amps. If this level is topped up to the appropriate level in all cells and the battery is put on charge to gain a FULL charge all should be good. If, you find the "water" level keeps going down on a regular basis, your charging system may be over charging the battery, and the regulator (control box) cut out may have to be adjusted to cut out at 14.5 V.

The other reason for cells or one cell to keep using "water" would be a weak cell or the battery is reaching the end of its useful life.

You did not mention what type of radio you installed. The newer type that have a clock in them usually have one lead that is wired directly to 12V which is "live" all the time, and a lead that is 12V switched. The "live"
circuit is to keep the computer alive and the switched is for radio power.

Vintage style radios usually have only one 12V lead and are usually tuned with an analogue faceplate. These have no use able circuits that have to have power maintained to them for proper use, just straight off and on.

The parasitic power drain with modern radios is very small but is enough to drain a weak battery in a couple of days or so.

Hope this helps..... CR
C.R. Tyrell

This thread was discussed on 08/05/2015

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