Alternator woes?

[Downlands]

I noticed recently that the ignition light has been glimmering intermittently whilst driving and on Sunday, during a trip out where I got stuck in traffic for a long period with the radiator fan on, the engine died. The AA came out, said I had an alternator issue, gave the battery a quick boost and I was able to get home.

I've now checked the battery voltages. Whilst idling, the voltage at the battery is only around 13v suggesting the alternator isn't working. However, if a rev over 1500rpm, the voltage reads 14.2v which I believe is about right.

Does this mean the alternator is fine and I just need the alternator to run quicker when the engines idling? 

I can't see what type of alternator I have but it's on a 2007 Duratec 2.0. It's a 3 month old Banner battery.

Thanks in advance.

Tim

 

 

 

 

 

 

[Tom_Arundel]

I`ve had that happen on a Sigma more than once. The Banner has quite low capacity, it`s ok for normal running but won`t last under high loads e.g lights and wipers on and running below 3K rpm.. If i`m driving with lights etc. on I run in a lower gear to keep above 3K and make every effort to avoid traffic but I realise that is not always possible. So yes there is a problem keeping the alternator running fast enough to charge the battery when it is under load in traffic. The problem is how to avoid over speeding the alternator at high rpm., a smaller pulley may fix the low speed problem but cause a high speed one. Keeping the revs up may help.(or a much bigger battery)!

There have been several posts recently about glimmering ign. lights

[Jonathan Kay]

Private Message sent.

[aerobod - near CYYC]

My R400D alternator has always struggled under high electrical load at idle. At 1,000RPM idle with minimal load it manages 13.0V (slight charge to battery), with fan and lights on it drops to 12.5V to 12.7V and requires 1,500RPM to bring it back to 13.0V, peaking between 13.7 and 14.2V above 1,500RPM depending on battery state of charge. Haven't had any issues with flattening the battery, but I also haven't typically run at idle for more than about 10 mins at a time with the fan running and lights and/or wipers on too.

I'm using a slightly higher capacity (32Ah) AGM battery though, that can tolerate deeper discharge with no ill effect compared with the Banner battery.

[Geoff Brown]

A member in my area who has a R300 Duratec was recently marooned due to the same snag even down to the volts increasing above a certain RPM when checked out after recovery.

The alternator was removed & bench tested & found to be 'nominal' but as a precaution the alternator was replaced as he & I  suspected that the regulator pack &/or something else in the alternator was suffering heat stress.

Unfortunately the under bonnet heat of a Duratec cannot be simulated during a bench test.

The alternator is either a CM550R or 551R right hand mounted when viewed from the front of the engine.  These are just about the best value: http://www.cambridgemotorsport.com/alternators?field_brand_tid_selective=37

[Downlands]

Thanks everyone for your thoughts and for the link Geoff. Will have to investigate further. By the way, I didn't receive your PM Jonathan just in case you're wondering why I haven't replied.

[Jonathan Kay]

It's still there... I'll send again.

[Piers300]

A warning light that is dimly lit, is often a sign of a diode failing and giving half wave rectification. I had exactly this on one of my old cars. You could have the alternator repaired and some repair shops may be able just to replace the diodes.