GT6 Mk 3 alternator, replace or upgrade?

[BrendanD]

Some advice needed. My GT6 mk3 has an LRA100 alternator fitted. It mostly does short trips, so I'm concerned to give the battery a sporting chance of a charge. The car is stock apart from H4 halogens.
Noticed a couple of things over the winter:
- wet night, in traffic, heater fan, demister, lights and wipers going, everything slows to a crawl if the revs drop below 1000.
- idling at 700, nothing else on. the ignition light comes on intermittently, goes off if I blip the throttle, but may come on again (not like its always on at idle, just 30% of the time). Indicators don't flash at idle but stay on, start flashing if I lift the revs.

Q1. Is my Alternator on the way out? (its about 3 yrs old)
Q2. Should I try and fit something a bit more powerful, I think the LRA 100 is 34A? If so what? The GT6 is kept under an apartment block in central London, so I won't have access to a vice or facilities to go fiddling. It needs to be a straight bolt on and off with a pulley fitted.
Tx

[piman]

Hello Brendan,

that alternator should be large enough for a standard car ?  I would initially check the fan belt for condition and tension, and also make sure that the main body to engine earth cable is sound. A larger alternator would not  necessarily put much more in your battery on your short trips. If your car starts easily then the battery shouldn't have a hard life anyway?

I have the same alternator on my P.I, which also has a pump to run and don't experience the symptoms you describe.

Alec

[BrendanD]

Tx Alec,
Fan belt tension etc is fine, earth cable is fine, and the the car starts well, I'm just concerned that at idle the alternator is not putting enough juice in and I'm going to eventually kill the battery.
Sounds like the alternator is not giving of its best, and needs replacing.....

[piman]

Hello Brendan,

it may be worth checking the brushes, they are very cheap?. Alternators are normally good at low revs, certainly better than a dynamo?

Alec

[Rich_s]

First thing i would check is the voltage at the battery on tickover, and then with the revs slightly increased, i have a brand new 18acr on my spit1500 and it charges at almost 14v when first started but drops to about 13 - 13.5 soon after and stays there even on tickover, have driven through the winter with halogen lights, wipers and heater going and all seems fine, might slow down slightly on tickover but not much, never had a problem with the indicators though.

rich