New car radio flattened my battery

[njc]

Car: 1996 Fiat Punto 55SX
Stereo: LG LAC3700R - £50 from Halfords on half-price offer

I installed the LG stereo to replace a dying Fiat original unit.
Worked fine, but I noticed the car was reluctant to start once or twice, and then today it wouldn't start at all.

I checked the current drawn by the LG unit when it was off: about 140mA (!!) which seems ridiculously high to me.

Now, my car battery may not be in tip-top condition but I reckon 140mA would kill even a fully healthy battery in pretty short order.

Anyway, the only caveat on all this is that Fiat Puntos (at least the Mk1 type) don't tell the stereo that the ignition key is out (i.e. the stereo has to be switched off manually). I guess there aren't so many cars out there that are set up this way?
So it seems possible to me that the LG unit might behave badly (i.e. 140mA draw) when it reckons the key is in (but why?) and then drop to a sensible draw when the ignition input is off (like <10mA I guess?).

So... I've already returned the unit for a refund, but I still need a new stereo and am a bit concerned that other stereos on the market might not like the Punto's behaviour of pretending the ignition key is always in...

I suppose I could attempt to rewire the system but I suspect the Punto's ignition assembly simply doesn't have the concept of an accessory position (though I could maybe use the ignition position somehow?).

Any comments/thoughts/tips welcomed.

thanks
Neil

 

[Gees]

You need a radio that has a a connection to the normally dead side of the electrical system. This "sense" wire tells the radio the ignition is Off and switches the unit accordingly. When you turn the ignition back on the radio comes on... The wire as you said above is usually wired to the ACC on the ignition switch so you can have the radio on while not running the engine.

 

[KingboyD]

140mA is not a big draw by any measure and would take some time to drain the battery! Have you checked the drain at the battery??

 

[Steve]

I fitted a new stereo to a Punto Mk2. It was fine. There's normally a yellow wire and a red wire. IIRC, the red wire is permenant pos, and the yellow is ignition pos. The yellow tells the stereo when the ignition is on. What you've possibly done is connect both pos wires from the stereo, to the permenant pos from the car. Most stereos come with this option, for cars without an ignition pos, and will allow the stereo to run continuously.

I know my punto had a strange ignition setup though. When you turned it off, it shuts off all the electrics, even the lights. If you needed to park with the sidelights on, theres a setting beyond off, to get into this position theres a button bext to the ignition to allow the key to turn, and you can then remove the key in this position too.

(think on the ignition, it goes III - II - I - 0 - P)

 

[GasMan1965]

I got 2 FTO's, 1 for the wife and 1 for me and bought 2 dvd head units which I wired exactly the same so they can be used with ignition off,, Mrs FTO started going flat regularly with a brand new battery so unplugged her head unit and low and behold its all fine after so have now wired to the switch live so ignition must be on and all fine now

 

[Stivino]

I think you'll find that on aftermarket stereos the yellow wire is for the memory so needs to be live (+12V) constantly. The red wire is the one that's switched (+12V) from the ignition.

 

[njc]

Thanks for the replies guys.
Some more thoughts and an update...

I agree 140mA doesn't sound like much at all, but if you work it out, it's about 3.5Ah per day. Car batteries don't seem to be sold by Ah any more, but a wee car like a Punto probably has a ~ 40Ah battery. Given that it's not brand new, maybe it's now 30Ah (maybe 3 yr old battery). The killer is that it won't start the car if it's not fairly full - I think I recall being told that 2/3 full is about the threshold for a lot of cars.

So now you've only got 10Ah you can safely lose, and about 3.5Ah per day drain. Not so long before you need the jump leads...

I did a lot of googling, and most car makers for whom I found a stated position on the subject say that the "parasitic" drain should be really small (like a few mA typically) with 20 - 30 mA being the limit above which the car is deemed to have an electrical "problem"...

Anyway
After returning the stereo, I thought "nah, can't be right, my car's not the only one like this", and called LG. They said the unit should be compatible with any car, and after consulting tech support (and their repair agents) the consensus was my unit must have been duff.

Bought another.

Identical problem.

Miniscule current when I remove the ignition wire, 140mA when I leave it in.
(Not sure I can face installing new wiring to pick up the ignition position directly.)

LG are looking into it for me...

 

[Spark123]

I have seen on a couple of occasions now getting the red and yellow wires the wrong way around can cause a flat battery.

 

[njc]

I have seen on a couple of occasions now getting the red and yellow wires the wrong way around can cause a flat battery.

On some cars I guess that's possible (and indeed LG asked if I had the wires the right way around).

However, on the Punto it doesn't make any difference, as both wires are at 12V, *all* the time. Herein lies the root of the problem

(And I presume it's the same for any car which doesn't kill the power to the stereo when the key is removed...)

Also I just checked which wire carries the current when it's drawing the 140mA and "off": it's actually the permanent wire to the battery, not the "ignition" wire. That surprised me a bit, but I don't know which one is fused in the main fuseboard. When the stereo is on and drawing 0.5A or more it's also still all flowing through the permanent wire. A bit odd, as the Punto has a fat wire to the "ignition" and a skinnier one to the permanent battery connection...

 

[Spark123]

Yeah, car manufacturers like to do things like that. The only other test I would have carried out would be to see how many amps the permanent live connection took whilst the switch live was disconnected.

 

[njc]

Yeah, car manufacturers like to do things like that. The only other test I would have carried out would be to see how many amps the permanent live connection took whilst the switch live was disconnected.

Yup, already did it. My multimeter was on the 10A range (didn't want to blow the fuse by using the 200mA range), and I couldn't see anything at all except a small short pulse of current on first connection, a few tens of mA probably. It's a pretty basic meter, so the current was less than about 10mA and beyond that I can't say

 

[Spark123]

Which means the key to the problem was having the switch live on power all the time. If you had somehow managed to connect this to the ignition then you probably wouldn't have had a problem.

 

[njc]

Which means the key to the problem was having the switch live on power all the time. If you had somehow managed to connect this to the ignition then you probably wouldn't have had a problem.

Indeed. But is it reasonable for a stereo to draw so much current when "off"? It makes it unusable in cars like mine (without modifying the car's wiring)...

 

[Spark123]

If it is designed to be connected to a cars ignition system then it is designed to take that current only when the ignition is on i.e. mostly when the engine is running and charging then it seems reasonable to me.
Would it be a big mod to take a wire from somewhere that is only live with the ignition on?
Another alternative would be to run a switch specifically to switch it on and off, however you'd need to remember to open the switch otherwise you'd get a flat battery which is why ignition is preferable.

 

[njc]

Hmm, maybe we're talking at cross-purposes here.

To clarify:
1. There are cars out there that do not cut the power to the ignition wire in the radio harness when the key is removed (of which my Punto is one).

2. LG assert that their stereo is compatible with any car.

I can't reconcile these two statements, given that the unit draws so much current when off.

Couple of reasons why I don't just mod the wiring myself: I haven't yet worked out where I could pick up an ignition signal; I haven't checked which wire is fused from the main board; I kind of like being able to run the stereo with the engine off; and most of all it's just a bit of a pain

I'm hoping (in vain no doubt) that LG will email me a firmware update to burn from a CDR. Fat chance!