weird electrical fault

Laura_t · Postby **Laura_t** » Sun Mar 08, 2015 7:01 pm

OK,
Last night on the way home from work, the battery and airbag lights came on, the radio stayed on but had no sound, the lights dimmed and the engine had no power. To keep the car running I had to turn off the radio, heater, driving lights, basically everything electrical except the headlights.

My husband checked the voltages at the battery today and had 12.4v engine off and 14.3v engine idling. We started turning things on, radiot, headlights, heated seats etc and the voltage dropped to 12.8v but everything seemed OK.

The only thing not working is the passenger electric window.

Anyway heading back to work today about 15mins into my drive at 100km/h same thing happens. Had to turn off anything electrical again.

We have no idea where to look for the fault.

pezchops · Postby **pezchops** » Sun Mar 08, 2015 7:40 pm

those symptoms fit a bad alternator ,
i know you say your hubby checked voltages but i still think you have a bad alternator

if you are in the RACQ call from home and tell them how you broke down .
even if it starts when they get there, tell them what has happened previously ..
they will check your electrics and should find the fault for you.
they wont fix

wait for a post here confirming my thoughts first, because im no mechanic.
just from experience with a life of owning older cars.

Laura_t · Postby **Laura_t** » Sun Mar 08, 2015 7:49 pm

We were wondering if it had something to do with the passenger window which now doest work.

Is there a easy way to test a alternator?

manga_blue · Postby **manga_blue** » Sun Mar 08, 2015 9:24 pm

I'd start by pulling the fuse for the power windows. If everything else starts working OK then it means there's a serious power drain somewhere in the windows circuit. No idea where that fuse is in an NB8A though: check the owners manual

pezchops · Postby **pezchops** » Sun Mar 08, 2015 10:56 pm

Laura_t wrote:We were wondering if it had something to do with the passenger window which now doest work.

Is there a easy way to test a alternator?

The following is for a Honda civic i owned that did the same as your mazda is doing.
The test i found when i researched the Honda forum.
have the motor running then disconnect the battery.
if the motor keeps running the alternator is ok...if the motor stops the alternator is no good.
I did this and the motor stopped so i replaced the alternator.
then when i repeated the test with the new alternator in the motor kept running.

the battery is only suppose to start your car...the alternator keeps it running.
just be aware when playing with the battery it is easy to stuff things up...my civic was bit of a heap so i didnt care

maybe better and safer you see an auto electrician

Laura_t · Postby **Laura_t** » Mon Mar 09, 2015 8:14 pm

Hi

Thanks everyone for your help. Last night the car died on the freeway and my husband came and towed me home. This morning the car started fine from the battery.

Once running we disconnected the battery and the car stayed running even with radio on. But as soon as you turn on the headlights or revved the engine, it would die off. Is this an alternator issue as the alternator was still putting out 14.3v when disconnected from the battery.

Thanks
Laura

project.r.racing · Postby **project.r.racing** » Mon Mar 09, 2015 9:13 pm

did you check the windows?

whatever the husband is checking the volts with, can if check amps?

Laura_t · Postby **Laura_t** » Mon Mar 09, 2015 9:28 pm

Windows are working fine again.

His multimeter doesn't do amps, and his electrical gizmos only do ac.

He thinks the alternator is breaking down and isn't putting out its maximum current.

Thanks
Laura

Mr Morlock · Postby **Mr Morlock** » Mon Mar 09, 2015 10:38 pm

It's weird that both of you are persisting in something you nothing about and no one is going to be able to trouble shoot it. Just do what is needed. Ie RACV for breakdown service and auto electrician to fix it. You did not mention how the car was towed ie on a tandem trailer but certainly not a tow rope which is not legal anymore. An intermittent electrical fault is going to happen again and its potentially dangerous.

Laura_t · Postby **Laura_t** » Tue Mar 10, 2015 12:47 am

Mr Morlock wrote:It's weird that both of you are persisting in something you nothing about and no one is going to be able to trouble shoot it. Just do what is needed. Ie RACV for breakdown service and auto electrician to fix it. You did not mention how the car was towed ie on a tandem trailer but certainly not a tow rope which is not legal anymore. An intermittent electrical fault is going to happen again and its potentially dangerous.

Thankyou Mr Morlock
I thought i would try posting about the problems i have been having with my 5 and most of the members that have taken the time to reply have been very helpful.
I was very im pressed considering this is the first time i have posted on the forum with how quick the reply came in and where very helpful confirming what i had thought the problem might be ,
yes the alternator is at fault so thankyou to them for there advice.
Mr Morlock thankyou for informing me of how to tow my car home and yes i could have called the RACV i,m sure they would have shown up 2 hours later only to tell me what i already knew
that i would need a tow then they would of happily left me alone on the freeway at 1am for another two maybe three hours for the truck to show up .
RACV might be great for some but i for one dont trust them they do not care about leaving people on the side of the road for extended amounts of time .
As a female its not a nice feeling being stranded in the middle of the night.Been there had that treatment from them.
As for mechanics absolutly last resort i,m afraid , no one touches my 5.
I have had my car for 8 years , not once has it failed me till now and i pretty much know it inside and out, why because i am not stupid i know how to work on every part of my car and have pretty much done all my mods, services and upgrades myself.
Its nice that you have tried to help me but i feel all you have done is try to be little me.

taminga16 · Postby **taminga16** » Tue Mar 10, 2015 9:06 am

Hats off to you.

Greg.

Mr Morlock · Postby **Mr Morlock** » Tue Mar 10, 2015 2:19 pm

They have breakdown services for cars because there is a demand and it is safer for the public. RACV do provide an excellent service esp Total Care and saves a lot of angst . I guess I fit into the category of believing that a trained mechanic or auto electrician knows more about their trades than me though basic work I am happy to do. Pezchops put it far less bluntly than I did "maybe better and safer you see an auto electrician"

bruce · Postby **bruce** » Tue Mar 10, 2015 3:15 pm

RACV guy told me my alternator was dying when he gave me a zapp last time. I replaced it. Then my battery died (but it was old).
I imagine it would be easy-ish to swap out an alternator on a north/south engine.

hks_kansei · Postby **hks_kansei** » Tue Mar 10, 2015 3:18 pm

When a car develops electrical issues, and you can't narrow it down quickly, it's best to go see a witch doctor, or an auto electrician. They both specialise in black magic and things that make smoke.

As for the problem you have, have you tested if you can make the problem occur whiel stationary? (ie: rev it in neutral up to the same RPM it sits on at 100kph ~3100rpm)

If you can do that in the driveway then you can put the multimetre onto the battery and check that the Alternator is still putting out the correct voltage (perhaps the voltage regulator is not working and it's over-charging..... not sure if that would cause the issues mentioned though)

I still think you should try disconnecting the windows and see if that makes a difference. Either find and remove the fuse as said earlier, or just remove the door trims and pull the plug from the motor.

I still think the witch doctor is the best option though.

hks_kansei · Postby **hks_kansei** » Tue Mar 10, 2015 3:21 pm

bruce wrote:RACV guy told me my alternator was dying when he gave me a zapp last time. I replaced it. Then my battery died (but it was old).
I imagine it would be easy-ish to swap out an alternator on a north/south engine.

From memory 2 or 3 bolts, and I think two plugs.

The hardest part is getting the new belt on since even with the adjuster backed right off it's tight.

if the OP does put in a new alternator be aware that NA and NB alternators are not interchangable.
The NA has a voltage regulator built into the alternator, the NB does not (NB regulates voltage via the ECU)