Have I fried my alternator and how can I tell?

[Andy Best]

I put my engine back in at the weekend all seemed OK then the ignition light came on after about ten minutes running .

 

How can I check what has gone wrong all seems to be wired correctly, been back through the build manual as a double check, I've searched the archives but struggled to find any direct advice .

 

The car is 97 1.6K with a standard two wire Rover alternator, I need an idiots guide to checking the alternator circuitry. If the regulator has gone is this a swap out item or is a new alternator needed, I'm a bit unsure of putting a new alternator on until I find the fault.

 

Thanks Andy

[John Howe]

Take your alternator to your local auto re-wiring firm (see yellow pages). They will be able to tell you instantly what is wrong and most likely fix it within 24 hours

..

 

JH

Deliveries by Saffron, the yellow 222bhp Sausage delivery machine

[philwaters]

With the engine running put a voltmeter across the battery terminal and check the voltage. If the alternator is running ok then you should see 13.4v or so... it does vary, but it will be higher than with the engine off.

If that checks out then it might just be the wiring to the light in the dash. Sounds more like the alternator though... and second the above.

 

Phil Waters

You mean you can drive these?

I thought it was just there to polish 😬

[Andy Best]

Thanks,

 

For your replies, if I need to check the wiring to the lamp how is it possible that the lamp lights and the alternator is charging?

 

I ask as I could have dislogged some wires under the dash.

 

Andy

[Andy Best]

Update,

 

Started tonight cold, no alternator light and volts higher at battery as described above then after 5 mins dropped to 12v and light came on which I thought was all a bit strange.

 

I waited for everything to cool down and tightened every nut on alternator and earth straps, looks like all is OK now (Needs a fingers crossed smily).

 

Thanks

Andy

[philwaters]

Sounds good Andy,

 

I should have added.... try putting the lights on and then the heater (if you have one) and see what, if any difference that makes. The alternator should compensate for the load and if it can't the light may come back on. However, the heater draws a lot of current so the engine may need a few extra rpm to spin the alternator fast enough.

The initial high then dropping voltage might just be the alternator having replaced the starting load/draw and returning to 'normal' running.

 

Hope it is all ok.

 

Phil Waters

You mean you can drive these?

I thought it was just there to polish 😬