Voltage drop at idle

Dras · Post by **Dras** » Wed May 27, 2009 11:59 am

As of just recently I have started to get voltage drops while my car is idling. The voltage drops below 12V for about a second and the radio cuts out.

My initial thought was the alternator. I removed it (that was a fun job) and had it reconditioned (new genuine Mitsubishi reg, bearings and brushes). I also replaced the car battery while I was at it.

Unfortunately, the problem has not gone away. The voltage seems to fluctuate at idle from high 11V to about 14V. The voltage is definitely lower when under load but the radio never used to cut out before.

The car is a tip GR with 160,000 on the clock. Besides increasing the idle speed, is there anything I can do?

Post by **Bennoz** » Wed May 27, 2009 2:24 pm

Could be bad earth .Try checking the earth connections from the battery.

Dras · Post by **Dras** » Wed May 27, 2009 2:28 pm

Thanks, I will check both ground and + connections.

I have checked battery voltages and I don't seem to be having any issues with the battery charging.

FTEvolution · Post by **FTEvolution** » Thu May 28, 2009 8:08 am

Bad earth or something arcing... if you can't track it to the earth, get it to a sparky. A car up in flames isn't something anyone wants to have to deal with

Dras · Post by **Dras** » Thu May 28, 2009 9:40 am

I couldn't notice anything loose or arcing but over the weekend I was going to measure the voltage drop from the alternator to the battery terminals (I read it should be less than 0.2V while the car is running). If that doesn't turn anything up I will take it to an auto electrician.

MuMan · Post by **MuMan** » Fri Jun 26, 2009 8:30 pm

You'll probably find it's the idle stepper motor. When the idle drops you may hear a relay cut in that unloads the alternator charging circuit to raise the rpm. Will normally drop to around 11v or fluctuate below 12v until you rev it.

payaya · Post by **payaya** » Sat Jul 04, 2009 4:00 pm

What is your idle speed when warm?

Dras · Post by **Dras** » Sat Jul 04, 2009 9:26 pm

I just replaced the o2 sensor and the idle stepper motor.

Idle when warm seems right to me, the needle sits just above half way between 0 and 1000 rpm.

The voltage still drops to 12V with the headlights and the A/C on at warm idle.

Post by **I8A4RE** » Mon Jul 06, 2009 9:43 am

Its probably the gauge itself. I wouldnt rely on it too much. Check voltage at battery and if thats sweet dont worry about it.

koolio1234 · Post by **koolio1234** » Tue Jul 07, 2009 2:25 am

I have been getting a voltage drop as well lately. It usually happens after sitting and idling in traffic with the music up. Not a big deal but I also get the flickering of my dash lights during idle. Off course it goes away when I start driving though.

Does this smell like the alternator is shitting itself? Anyone?

Post by **I8A4RE** » Tue Jul 07, 2009 9:03 am

koolio1234 wrote:I have been getting a voltage drop as well lately. It usually happens after sitting and idling in traffic with the music up. Not a big deal but I also get the flickering of my dash lights during idle. Off course it goes away when I start driving though.

Does this smell like the alternator is shitting itself? Anyone?

Yeah it does mate.

KaGe · Post by **KaGe** » Mon Jul 20, 2009 1:17 am

Had this with mine, turned out to be the regulator in the alternator. Does the alternator seem to get overly warm? If it does it's a sure sign. Total prick to remove the alternator as most of you will know. And around $700 to get it overhauled as it's computer controlled (4-pin). Make sure you find a decent auto sparky that knows his sh*t.

Post by **I8A4RE** » Mon Jul 20, 2009 8:00 am

^^^^^^ $700 dude thats way toooooooooo much. Buy 2 brand new ones for that price

midi · Post by **midi** » Mon Jul 20, 2009 10:04 am

koolio1234 wrote:I have been getting a voltage drop as well lately. It usually happens after sitting and idling in traffic with the music up. Not a big deal but I also get the flickering of my dash lights during idle. Off course it goes away when I start driving though.

Does this smell like the alternator is shitting itself? Anyone?

My FTO currently does the same koolio. I'm avoiding night driving until I can get it fixed as the constant start/stop of traffic lights can quickly drop the battery gauge to under 12v.

Although I must admit watch the gauge with the indicators on is almost hypnotic

justbecause · Post by **justbecause** » Mon Jul 20, 2009 1:41 pm

Yup Bad Regulator...

its like 60 bucks in my country to fix that..... or should i say about 27 AUD ..... lol....

to prevent that I use voltage stabilizers..... very cheap and effective....

I never had voltage problems in my cars.... my friends do.....