Lovemyevo2

I've got a new problem, which is a regular flat battery. I've had the battery tested at my local tyre centre, who said it's fine.
In it's normal switched off state with everything plugged in I get 150ma across the terminals. When I unplug the (new) stereo and the (original) digital clock this drops to 130ma. When I unplug all the fuses one by one there is no difference. The only relay, when it's unplugged, that makes a difference is the headlight one, which is only 6 months old from Porsche. This drops it to 100ma.

Sometimes the battery drains over a few days. Sometimes in just 8 hours, while I'm in the office. It's not completely dead, just enough to not crank properly and start.

It might be a nasty coincidence but this started happening (after 1.5 years of regular use and no problems) when I had a new stereo installed, plus an amp and subwoofer in the spare tyre well. The installation was done properly, all fully fused and switches from the amp to the head unit.

Has anyone got any ideas of what might drain the battery at standstill, that's not fused?? Is the drain I'm quoting normal? Should the headlight relay take 30ma when switched off?

Any ideas or checks would be much appreciated. Mr Merlin, on review of your previous posts, I'll see if I can find someone with an IR gun - not sure where I'd find this though!

neilh

IR gun is an easy and cheap find:
http://www.ebay.co.uk/bhp/infrared-temperature-gun

A 100ma drain should not be killing you battery over a short period, around 30 - 35ma is normal, the amp and sub-woofer may be getting power all the time, i would pull the plugs on these as well and see what happens.

James Bailey

disconnect the power supply to the amp and radio...see what happens.

Bucko74

I have exactly the same problem. No so severe....would take a few days to flatten, but frickin annoying. I dont have an amp in mine at all either.

I'm no sparky so I had one spend nearly four hours pulling wires and waving his meter around. In the end for nought. I just fitted a isolator on the battery and left it at that. started setting the clock everytime I took her out, but I dont even do that now.

Good luck finding the problem.

snoz

^^^^ James abd Neil said exactly what I was thinking. Is the amp wired directly to the battery?

James Bailey

in this country sadly enough Radio installers usually are paid a flat rate per install....needless to say the do it very, very quickly. And never ever bother to even LOOK at a 928 wiring diagram let alone understand one..... They just fish around for a switched hot lead and splice into it NO MATTER WHAT IT HAPPENED to be !!

Alan

Yes.. start there disconnect the whole thing.

Other culprits are fried alternator diodes - simply disconnect the alternator and see what happens to the drain (both leads off). BTW do this with the battery disconnected - isolate the connections (insulate the wire ends) then reconnect.

Alan

gsmarrara

New stereo sindrome. Happened to me. Was using the new stereo at full volume to enjoy the investment, everything installed correctly. But the amp was draining 90 amps in a car with a 100 amp alternator. So, conclusion, the car never had the chance to really recharge the battery. Try to use in a lower volume in the last 10 minutes of your commute.

Lovemyevo2

Thank you all for your comments. The stereo and amp were all installed carefully and connected direct to the battery (conveniently positioned in the same tyre well!). We also pulled the amp fuse as part of the investigation - no change to current drain. gsmarrara - I don't play it too loud (having previously owned an E46 M3 with a factory sub, I like nice crisp bass, which it's very difficult to get with speakers that fit in the standard spaces!) it's certainly worth investigating the drain when the amp is running. On that thought it's probably worth checking the alternator output - although seems fine i.e. 13V on the dash meter. Thanks Alan, I'll check the drain with the alternator disconnected to see if it's a fried diode.
Thanks Neil - if all the above fails we'll start checking temperatures of components.
I'll report back in a week or so as I'm off on hols and leaving it with my mechanic!

SteveG

I'm also not an electrician, but I believe this statement is contradictory, and is the root of your problem; it should not be wired directly to the batt.

See Mr. Bailey's post, esp. "switched hot lead"

There are many threads on this subject, but I don't know if any of them recommend what switched circuit(s) are appropriate for an amp. Maybe someone could do that (sep thread) for the various years.

Alan

The amp SHOULD go direct to the battery (via a big fuse), The head unit should have both switched & permanent supplies - I'd check this next - just pull the whole head unit out - what happens to the drain.

You have to think back to when did this first start happening, and what other changes - if anything - preceeded that...?

Alan

Lovemyevo2

The amp is connected to the battery with the correct large fuse. I've pulled the plug out the back of the head unit and the results were as per my original post. Same as pulling the blade fuse from the amp. All the audio kit that has gone in is brand new and was fitted carefully, which is why I think it's coincidence. It also doesn't seem to be draining the at standstill wen switched off. I've not yet got the results of alternator output and drain when audio is switched on but this does sound interesting. I had the alternator refurbished about a year ago as it failed totally. I don't know what parts of this component were changed then. I'll report back when I've got these figures. Thanks Tim

tailpipe

Diodes are shot aka leaking in the alt.

Alan

BTW - normal drain is approx <30mA - ideally about 15mA. Aftermarket equipment - including audio - may make this ideal number impossible to reach.

The HL relay should take no current when it is not operating.

I really don't think its very likely that the timing is a coincidence... Did you install the audio yourself? I'd be checking for the secondary effects - screws for mounting things screwed into looms behind panels etc.

The B pillar passenger side by the woofer is a prime spot for this - did you change the speakers?, doors are another possibility - change those speakers? - how & where is the amp mounted?

Are you sure the connections in the colsole are to the right things? could there be a connection to the lighting circuits. Does the current also drop when you remove all the HL fuses (x4)? when you remove the HL motor fuse (x1)?.

Have you tried removing the extra connections at the battery positive post - most of these are unfused feeders.

Alan

Lovemyevo2

Mmmm, the drain from headlight relay is a worry. I haven't pulled all 4 / 5 fuses at the same time. But pulling them one by one didn't alter the drain at all. Previously I did have headlight problems (subject of a previous post), where the main lights wouldn't go onto full beam - bumper ones did. But after sorting a few sneaky loose wires in the CE unit whilst hunting for a horrible misfire problem (subject of yet another earlier post, which just turned out to be bad plugs!) this full-beam problem was sorted.

On the audio, If I rewind a bit, it might help: I had a very old head unit and standard speakers when I bought the vehicle. My company arranged for a Parrot handsfree kit to be fitted a year or so ago by a professional fitter, which because the head unit was so old, was connected direct to the speakers after the head unit. Worked okay for a while but the sound was rubbish as the speakers were clearly passed their sell by date. Plus an amp wasn't going to work well with this arrangement.

So, time for an upgrade for that crisp bass I wanted! My mechanic did the work (with me standing watching!) as he's got lots of car audio experience. We pulled out the parrot and the old head unit and replaced with a head unit with integrated Bluetooth. The standard loom from the dash to the front /rear fader **** (on the right hand side of the driver's seat) was only two channel in. So we took another set of wires back from the head unit under the driver's seat to bypass the fader and allow the system to operate as a proper four channel from the head unit.

I replaced the front speakers with some extra thin ones I found online that would fit without any alteration to the door. As it happens, once these were fitted the drivers side didn't work. It turns out that one of the wires between the speaker and junction by the fader didn't have continuity. So a new wire was used here in the door. The rear speakers were replaced with 6 inch ones as a straight replacement to standard
An MDF box was created to fit in the spare tyre well and hold the sub plus the amp is screwed to this box (so it's all one unit that just lifts in and out allowing simple access to the battery (lucky given how many times I've had to access it to jump start the car recently!!). Connectors have been fitted so the whole unit can be disconnected and lifted away if required. The audio feed and switch wire all come back to the amp from the head unit.

So not much has been changed from standard apart from bypassing the front / rear fader potentiometer, soldering into the audio loom (which seems like it's all been done correctly including the switched and constant lives), replacing the old speakers with direct replacements and adding a wooden box with the sub and amp into the spare tyre well…(i'll post some pics when I'm back from hols and the car is back from garage)

But, it doesn't seem like the problem is with the audio system as when the plug is pulled from the head unit it doesn't change the drain. I take your point Alan on the secondary problems that may have been caused and we'll double check, but we really haven't done much alteration to what was there before

Yup, we pulled the other feed off the positive post (think this goes direct to fuel pump) and no change to the drain.