Offroad-Express

Hi there, I have a 95 mistral (square headlight) td27 auto and my battery voltage reads 14.4 at idle, but with increased revs upto 1500rpm it seems to get up to 15.6v and is increasing. With moisture around the battery caps, I'm guessing that it's overcharging due to a faulty voltage reg. In the alternator? . Any thoughts or advice would be great. I can change it if it is, but want to know if this is correct and then if so, where to go to get a voltage reg. That won't cost a small fortune.
I'm also guessing my battery is stuffed due to it being almost completely flat after a 20 minute drive. I'm in Christchurch. Cheers.

I'd say its over charging because your battery is fooked. not the other way around.

sounds like you have a crook cell or three in the battery so there is no way for the alternator to tell so it goes to full charge as it is started.

Get your hydrometer out and test each cell.
Also make sure you top up your battery with distilled water.

Crash bandicoot wrote:I'd say its over charging because your battery is fooked. not the other way around.

sounds like you have a crook cell or three in the battery so there is no way for the alternator to tell so it goes to full charge as it is started.

The battery condition has nothing to do with over voltage from the alternator unless the battery is open circuit. The hitachi units on these will over charge for 2 reasons, either the sense wire is not connected or the reg is shagged. The dampness on the battery is because it is being boiled and this will have done damage to it.
Depending on which alt you have it shouldn't be too expensive to get it repaired.

ChurchurDan wrote:

Crash bandicoot wrote:I'd say its over charging because your battery is fooked. not the other way around.

sounds like you have a crook cell or three in the battery so there is no way for the alternator to tell so it goes to full charge as it is started.

The battery condition has nothing to do with over voltage from the alternator unless the battery is open circuit. The hitachi units on these will over charge for 2 reasons, either the sense wire is not connected or the reg is shagged. The dampness on the battery is because it is being boiled and this will have done damage to it.
Depending on which alt you have it shouldn't be too expensive to get it repaired.

you answered it with the first sentence. and if it's a mistral it will be a bosch unit unless it's been changed again since it was imported.

If the battery was open circuit he would not have been able to start it then drive it till it went flat. Also if it was open circuit the voltage would be high from the time it was jump started and the leads got removed.
I have never seen a bosch alt on an early mistral, they all have the 60 or 70amp vac pump hitachi unit. Bosch starters I have seen on them but not an alternator.

Yes its an hitachi LR160 type and yes the battery is stuffed and I'd say it's been doing it for a while

I have removed the alternator and replaced the voltage regulator, re assembled and refitted to truck.

Same fault, battery goes from 12.4v to 15.7 within 30 seconds .

Removed and dis assembled alternator, replaced rectifier
Re assembled and re fitted, replaced battery.

Now all seems to be good, I'm getting a constant 14.2 on battery terminals when running ad it doesn't increase with the revs like before. Thanks for the advice as always guys.

Cheers, stevo