I had a recon. alternator fitted to my 1.7D Astra (Isuzu engine) at the week end. The relay in the footwell was changed and the wiring checked. However there seems to be a fluctuation in the output. I noticed yesterday that the rev counter was fine at 70 mph (approx 2700 revs) but at 40mph the pointer was not steady. When I first started this morning the charge light was flickering on at idle speed and when coming to work the dash lights were not steady until approx 60 mph. When I pulled into the car park at work I was able to see the lights in one of the windows and there was clearly an alternate dimming and brightening of the head lights.
I was always given the impression that the alternator should produce a constant output capable of covering all of the general electrics even at idle speed and this, to my laymans eyes, would indicate that there is an output problem. Before I check with the supplier have any of you guys experienced this problem?
Any advice would be appreciated
First thing I would do is check your battery terminals. Similar thing happened with my previous car, Mk2 Cavalier. In my case it turned out to be a high resistant joint between battery and terminal. It got so hot that the heat cracked the battery around the +ve post. The engine always started fine, but the charging light was always flickering, as were the headlights.
Thanks for the advice. Will check the battery terminals later but I changed the -ve terminal a couple of weeks ago, cleaned the +ve one and battery earth lead. My problem is the opposite of yours. The battery seems to hold less than half charge and it struggles to start. Another problem is that I only get live approx 15 mins from work so I am not sure that it is enough time to recharge the battery and it does not charge enough overnight on the charger. How can I check the output from the alternator and battery?
So what was wrong with the original alternator?
How old is Car/Battery?
Diesels do take a fair old whack of current to start them, more in winter of course, any poor electrical joints need need cleaning/tightening/layer of petroleum jelly on all surfaces.
Have you checked the pos and neg battery leads, particularly the neg one from engine block to chassis and battery?
If you have a voltmeter, you should be looking for approx 13.5 - 14.0 volts at the battery terminals with every electrical item on car switched on, and the engine running at a fast idle. Good luck.