Conference terri::cars_uk

    I had this symptom on 2 cars :
    
    1. Vaux Belmont. Replace bad fast-on connector on Alternator,(looked
       OK).
    
    2. Talbot Horizon. Replace fuse-carrier due to high resistance pin.
    
    Both times the fault never re-occurred after corrective action.
    
    Tony.

	A couple of things:

	(1) sounds like a bad connection somewhere, I'd guess that the alternator
	connections are ok (based on garage visit this morning), but I'll
	check them anyway.  Indeed, I'll be checking all of the connections
	that I can get my hands on.

	(2) how do you end up with a high resistance pin?
	
	Dave

    The first place to look is the alternator. If the alternator fails to
    charge then the the running voltage typically drops from between
    13.5-14.5 to 11.5-12.5V. Some instruments, notably some types of water
    temperature guages, oil pressure guages and fuel guages require a
    stable 12V supply, sometimes derived from a solid-state or bi-metal
    strip 12V regulator behind the dashboard. When the alternator ceases to
    charge, the voltage drop will often cause a drop in the output voltage
    from  these regulators, so some or all of the above guages may give
    strange readings.
    
    Virtually all modern cars (post '75 ish) use alternators with in-built
    regulators which are self-energising. This means that there are only
    two connections, one large output connector, and one small connector to
    the warning light. It is worth checking that these connections are
    tight. The symptoms that you give suggest that the highest probability
    is that there is a loose connection inside the alternator, particularly
    if the symptoms reoccur on cold wet mornings. If this is true then the
    problem will get worse, which at least has the benefit of making it
    easier to track down!
    
    There are other possibilities, mostly loose connections in other
    places, but they would typically result in other problems occurring in
    addition to those stated. 
    
    Brian

    I also forgot to mention the brushes. If the alternator has seen good
    service, typically 50,000 miles +, the brushes, which supply the
    energising field to the rotor via slip rings, may be worn or sticking.
    This can cause the symptoms that you observe. The accessibility of
    the brushes varies considerably from alternator to alternator. But, an
    hour's work and a couple of pounds for new brushes is a lot cheaper
    than a new alternator....
    
    Brian
    

	When the chap measured the battery this morning he quoted figures of
	11.5 when idle and 13.5 when revving (mildly).  Is this too low?
	The alternator is just over 5 years old and has done 23000 miles.

	I'd also prefer to fix this *before* I break down!

	Dave

    ...High resistance pin...
    
    A fast-on spade connector had a pin on the other end which was badly
    crimped into the fuse block motherboard, causing arcing/volt drop.

	I've discovered part of the problem.  As with all intermittant
	faults, it became permanent last night.  On the way home, the 
	ignition light came on and stayed on, my indicators stopped
	working, my fuel and temperature gauges read nil.  When I got
	home, upon inspection I discovered that the relevant fuse was
	corroded (how?).  Once I'd cleaned up the contacts and inserted
	a new fuse, everything was OK.  Well, nearly OK, the ignition warning
	light is still occasionally glowing.  Its intermittant (ie sometimes
	nothing) but the intensity of the light varies with the revs (high
	revs = bright light).

	I suspect either the alternator, or the connections to it, so I'll
	be dismantling the alternator this weekend.

	Dave

       >>As with all intermittant faults, it became permanent...     
       
    Oh how I wish this was true!
    
    
    Phil Gill.
    Field (customer) service.

	I think that I've fixed it.  Yesterday I had the alternator apart
	and it looked just fine.  So, I re-read the (Haynes) manual and
	noted that it said:

	"...before you attempt to repair the alternator make sure that 
	the fan belt is correctly adjusted and that the battery is 
	correctly topped up."

	I had already considered the battery and topped it up to the 
	required �" above the plates.  However, in desperation I made
	up some distilled water and topped it *all* the way up this 
	morning.  About half way to work the ignition warning light
	went off.  Nothing I could do provoked it to come on again.
	
	So, maybe I've fixed it and maybe you'll be reading another
	reply...

	Dave