my battery light comes on when i brake. i've noticed it gets brighter with light on or wipers or elec windows are pressed.

my rev counter also reads a lot lower than the actual rpm when i for the first 20-30mins or so after the car is started...i've changed the rev counter a few times but always had the same issue.

could it be a dodgy alternator???

anyone had the same problem? whats the best way to go about diagnosing the issue?

cheers
ste

 

yes you have a voltage issue probably a dead alternator
the reason the light gets brighter is your using power operating the windows etc
get a multimeter on the battery with the engine running you should be seeing 14volts if not the alternator isn't charging

steve

 

That is not true, old charging systems never make anywhere near 14V, despite what others may tell you, the typical voltage is around 13.5-13.8V IME.

I would say your alternator is fine, as said though the first thing is to see what power you are getting.

The fact the rev counter reads lower means it is probably means it's not getting the supply voltage it needs, (are the warning lights also dim?) I would check the voltage to the cluster etc with the engine running, chances are it's ALOT lower than the power that is at the battery, this is usually due to crappy old fusiable links (I suspect Escorts have at least one). It could also be there is a bad ground.

The way the warning light works is that it has equal potential on both sides, when stationary one side of the bulb is grounded and when running, thus charging, it becomes live, hence the bulb extinguishes.

If the either side has lower voltage than the other the bulb will illuminate, hence it could be the supply voltage that is lower rather than the charging side, it's a crude operation and it isn't foolproof!

Martin

 

martin, thanks very much, thats great. i'll get my mutimeter out tonight
ste

 

I take it 12.65 across the battery with the engine running is too low then? just checked and thats what its reading

cheers

 

How old the battery ! Is it the right amps(when i bought mine feller said to me i just put a new battery on it! It was!! Just wasnt the right ampage got fucked in no time!) dont assume it ok swap it over with one from a motor without any issues ! Try it if still has problem then get your muilti out!

 

Yes, that is not actually charging and I am surprised you haven't had the battery going flat, the voltage needs to be above the open circuit voltage of the battery for it to be charging, next measure the power at the output terminal on the alternator itself, what is it? But yes, in this case it does sound like the alternator itself may be faulty or the 'regulator'.

@ "the fox" the amperage doesn't really make no difference, it simply means how much current it can supply before being discharged over a period of time, measured in (AH), the higher this figure is the higher capacity of the battery, remember when running the alternator supplies all the power and charges the battery in addition. CCA can be a factor though, but then it's not like an RST has a big, high compression engine.

Martin