battery, alternator or starter motor?

[richardpalinkas]

hey, for a while now i have noticed this problem, when i start my car from cold it starts perfectly with no trouble. however, when the car has heated up, the car will have like 3 realy slow cranks before it will start, and its slowly getting worse, today it nearly did not start.

i checked the voltage of my battery when car is off, which was around 12 ish, and when running it was at high 13's, but during the period when i crank it over and the car is hot, voltage dropped down to like 7, 8, 9 volts.

just wondering what the normal voltage drop should be, and what i should look at replacing. the battery is only a year old, and i dont want to replace anything that i dont need to.

thanks for your help.

richard

 

[showbags]

get your battery tested. sounds like it's just about dead.

 

[wortus]

The battery voltage will drop to around 9 volts when cranking as the starter motor draws a lot of current. You can take it to an auto elec and get it load tested.
If the car is hard to start when it is cold check the electrical system look for spark plug leads that have too much resistance, worn or fouled plugs etc.

 

[richardpalinkas]

thanks for the quick replies. like i said before, when the car is cold, it starts perfect. it is only when it is hot i seems to crank slow, like a dead battery, but i dont know why it would be when its hot only.

 

[axemurderer101]

maybe put a charger on the battery for a while then see how it goes

 

[keza87]

I have noted a few VT/VX commodores that do this including my own. I put it down to a bad earth somewhere but CBF finding it just yet.
Car still starts without fail and this is also with a brand new battery, old battery did the same thing!

 

[PRAVX II S]

You say that when you start the car when cold it starts fine and when it heats up it struggles to start.
There could be a loose connection on battery,starter motor,Earth wire. When these connections heat up and are loose they cause high resistance.
So check the battery terminals clean them and tighten them and check the starter motor wires clean them and tighten them.
And 9 volts drop when cranking is normal drop

 

[richardpalinkas]

ok thanks for letting me know the voltage drop, i have checked the battery connections, havent checked the actual earth cable as it is all with the other cables and cant see where its bolted to. ive checked the starter connections, might try and clean them and see if that helps.

 

[BerlinaBen]

Checking all the cables would e my first place to start as well. The cables to the starter motor is where i wpuld pay particular attention. If not the cables, then my next bet would be the solenoid on the starter motor.

 

[accentstencil]

When I had the same symptoms I replaced the starter motor which fixed the problem.