battery drain issues and alternator wiring

[GazzaG60]

guys

a couple of questions for the electrics specialists

one of the last things I had to do was wire up the alternator.

I know the s2 wires go from the alternator to the fuse board. on the 16v it went battery to starter. I have wired it back from alternator to starter. see 14.x v when running.

is this right or should it go to the fuse board and for what reason.

second question

I have an old amp and a set of audiobahn components in the back with x overs. when I tested it yesterday after about a couple of mins of running the battery was flat.

why would it flatten the battery so quick? happens with it running or not.

I don't usually have amp and speakers amped in my car. never did in the s2. last use was in my corrado and never an issue.

battery is brand new and 750 amp.

cheers

[Pirvu Eugen]

couple off minutes?!!!!
750 AMP?? And no fire?
Something is really bad there!!
Short circuit!!

[GazzaG60]

sorry battery spec is

Amp Hours: (Ah): 72Ah
•Cold Cranking Amp: (CCA): 720CCA


no fire no heat. all looks normal. battery is at like half (on charger) but charges to full again in minutes

I have a stereo with a touch screen and was running movie from usb stick.

never had this before stereo refitted. would fire up for a week or so with no alternator. not driving it yet. would run alarm for 3-4weeks

suspect amp?

[RichLV]

Disconnect the amp and check again. Had a similar issue in my UrS4.

[GazzaG60]

will do. its gotta be the amp. it must be like 12-15 yrs old now. what did you do replace amp? saloon sound is so poor. not that I use it much anyway or can hear it for the exhaust.

how about the alternator wiring?

any ideas. I presume using the fuseboard helps stop the lights dimming etc when stuff is turned on?

how about the second wire to the dash? I don't get a battery warning with it not connected?

[RichLV]

I replaced the amp wiring. It was wired by, terribly sorry, cripples, I rewired it completely properly.

Are talking about an S2 or VW wiring? If S2, then it should be wired like projected at the factory, because Audi's have a load reduction wiring contacts after the start. I don't remember on the S2 but if I remember correctly it was contact (relay) 75x on the C4 chassis.

[GazzaG60]

what was wrong with amp wiring. what did you do to fix? I have battery in boot and wires going to amp from battery.

audi 80 16v Quattro converted to s2. 16v used an older style battery-starter-alternator wire.
aby uses battery-starter and battery-fuseboard then alt-fuseboard.

im happy to do without amp. also I will rewire the alternator at some point but want to try to get the car on the road and moving so I can see what else needs looking at. just want to make sure im charging battery. I presume I am cos I get at battery 14.x when running and 12.x when not?

[RichLV]

Amp wires were too thin and no fuse for the positive wire. Besides, the amp control wire, which should be wired to the radio, was wired to a seat heater button and was controlled from it. Forget to set the seat heater to 0 and car doesn't start the next day because the amp does not go offline.

I would wire it as ABY requires.

If you would not charge the battery, a light would come on the dashboard. If the battery terminals show more than ~13.4 volts when the car is running, you're good, it is charging.

[GazzaG60]

I think my amp wires are too thin for sure but they don't get hot. wiring to amp trigger is good I put that in when trim was out. ill disconnect it for now

battery is charging then. so im good to test. I get no light on dash with alternator disconnected but if battery goes below say 11v it comes on?

I will put the proper wires in once I make um up.

[RichLV]

You should get the dash light if the blue (charging) wire is disconnected from the alternator. I cannot say more, because I haven't seen the 16v wiring.

[GazzaG60]

i have aby wiring looms for engine and dash. rest is 16v.

16v had the single blue wire in the loom for it. the aby doesn't have it in the looms or I cannot locate it. in the wiring jungle.

I looked at the diagrams for aby and its a single wire back to the clocks. ill look for the wires after my first drive of the car. hopefully later today.

[Tonybolony]

guys

a couple of questions for the electrics specialists

one of the last things I had to do was wire up the alternator.

I know the s2 wires go from the alternator to the fuse board. on the 16v it went battery to starter. I have wired it back from alternator to starter. see 14.x v when running.

is this right or should it go to the fuse board and for what reason.

second question

I have an old amp and a set of audiobahn components in the back with x overs. when I tested it yesterday after about a couple of mins of running the battery was flat.

why would it flatten the battery so quick? happens with it running or not.

I don't usually have amp and speakers amped in my car. never did in the s2. last use was in my corrado and never an issue.

battery is brand new and 750 amp.

cheers

Can I ask you about the battery? - A 72Ah battery has got a fair amount of grunt, but only if it's well charged. I bet the bloke who sold it to you, told you it was fully charged on the shelf?
For my business we buy 110Ah batteries, usually 10 at a time and customers regularly ask if they are fully charged. The answer is No, and my suggestion is always to charge them for 3 or 4 Days before use (These are deep-cycle caravan batteries, and if put immediately into service on a caravan Not connected to 240v, then they won't last long; whereas a battery that's been sold and fitted to a vehicle, and the vehicle then started- the battery is on charge immediately, and will slowly reach a high state of charge over the ensuing days of use.)

My guess is that your battery was in a relatively low state of charge to start with (enough, maybe to start the car once, at which point the alternator does it's stuff), in which case I would suggest slowly charging it for 3 or 4 days, regardless of what the charge status is shown on the charger, before doing anything rash with the car or ICE.

Just because it was bought New, please don't assume (as one would with a Duracell) that it's charged

[GazzaG60]

when I say new I mean nearly. I got it a couple months back. its been charged a couple of times. charger may be a bit iffy.

its on charge now. has been for a day.

hopefully you are correct and its just not charged enough.

didn't test it today. will do tomorrow. hopefully itll be better then. ill start without the amp which to be honest is the least important bit for me.

it was more the rate of discharge that concerned me. from a quick turning starter to basically nothing.

im sure it doesn't help that I am not driving the car. just testing and the when flat recharging it.

[Tonybolony]

Unless you have good quality, calibrated test equipment it's easy to assume incorrectly....
A 'New' battery that is fairly discharged can show a good reading on an average digital meter. Ie 12.8v is well charged but closer to 12.0 is flat (obviously off charge or load), the difference is that given the sort of load that the Amp is taking, starting from 12.8v the voltage should hold up well for some time, but starting from 12.0 (or below) it'll drop like a stone.
Just one other question- you hinted that the battery wasn't fresh from the factory?
Is it possible that it has been left flat, on a concrete floor, in your shed during below zero weather? If that is the case, then it's life will have been seriously shortened

Leave it on slow charge until Monday, and give it another go.

[GazzaG60]

got the battery a few months back. its an exide premium 5 yr version. its been on the car for alarm and electric testing during the build. first start was about 3 weeks ago. it started the car fine every time unless flattened by me doing stuff. same prior when testing. id then charge it for a couple of days and it would be good for another 3-4 weeks.

will do. I plan to run the car either tomorrow or over weekend. its not been left flat for sure but not exactly conditioned properly.

agree just cos it shows 12v don't mean its got the power to do much. it pretty much always shows 12v even if its not a "goer".

ill post some pics and a video of its first venture to the road in nearly 3 years over the next few days.

cheers