Peculiar alternator charging/ign light on

Post by **PSL184** » Wed Oct 29, 2008 7:46 pm

Ha ha.. well the b*****s will have anything if they can... but every little bit helps !!!

Post by **M_Temple** » Wed Oct 29, 2008 9:59 pm

Back to the original problem......

Some very weird developments (aren't they always electrical)
The original problem of the ign light went away (they never do) and the light went out quickly on starting, but I had a dodgy fuel pump (arm kept 'sticking' with contacts open), and no amount of adjustment would change it so needed to replace it. Fitted new SU one today, went for drive 8mls no problem. Stopped outside my garage on return to check no leaks before I put the car away, and on restart problem with ign light reappeared (they always do) and pump keeps 'ticking' - about once every 20secs as long as ign is on. No evidence of leaks from pump or carb. Checked volts again 12.4v across battery with engine stopped, 14.4v with engine ticking over and ign light glowing.

Anyone any theories how these two things could possibly be related? If they are coincidental anyone any idea why the fuel pump would operate in this way?
Dodgy ign switch?? This seems to be the only link electrically between the fuel pump and the charging circuit.

???????????

Post by **bmcecosse** » Wed Oct 29, 2008 10:14 pm

Pump ticking like that is normal enough. With these volts readings it appears alternator is charging - but perhaps earlier excursions with possible bad connections have now damaged the diode pack that controls the red light!

Post by **M_Temple** » Wed Oct 29, 2008 10:26 pm

Just to be clear the pump 'ticks' when the ign is on, but the engine isn't running. Surely this isn't normal - if it was the only problem I'd suspect the tank inlet pipe connection to the pump is leaking some air in...

Post by **bmcecosse** » Wed Oct 29, 2008 10:28 pm

Well - you shouldn't have ign ON when engine not running anyway - it will fry the coil! But yes - a tick every 20 seconds is normal enough.

Post by **M_Temple** » Wed Oct 29, 2008 10:37 pm

Well it was only for a minute or so while I took some voltage measurements!!
Anyway I am reassured by your comments that I only have one problem - that of the ign light/charging. I will swap the alternators on the two Travs over the w/e and see what happens.

Post by **bmcecosse** » Thu Oct 30, 2008 5:43 pm

Two Travellers !! Good idea to do the swap - will be interesting!

Post by **M_Temple** » Sun Nov 02, 2008 5:30 pm

Did the swap today. Good news and bad news (as always!)

Good news: Putting the suspect alternator (Lucas 11AC from MGM 18mo ago) from the '62 Trav on the '69 Trav produced the same ign light effect - including the same 14.5v across the battery with the engine running. Putting the Quinton Hazell (from Bull Motif earlier this year) version on the 62 Trav and all functioned normally - light went out quickly on engine start. So 'good news' is that problem appears one dimensional and simple (if costly) to fix - get another alternator.

Bad news: replacing an alternator after 18months and probably <1000 miles (the 62 has drum brakes, no servo, no separate indicators and so is a bit risky for everday town use in the SE - although the 948 sings like a bird and it handles much better IMHO than the 1098 '69)

Apparently there's a bloke in Redhill who specialises in dynamos and alternators - I think I'll take the dodgy one in to him to test and see what's what (given the fault on it is intermittent) as well as seeing if he has a reasonably priced replacement. If anything interesting comes out of it I'll post another response. Thanks to all.

PS. I agree with the comments re battery isolator and fuel pump switch. I installed both on the '69 (the isolator through the bulkhead above the parcel shelf as advised on this forum - works really well and easy to access).

Post by **PSL184** » Sun Nov 02, 2008 8:55 pm

Glad you've sorted the problem and the "new" alternator could have been "kippered" by that isolator bar you were using. My local "little old man in a shed" recons alternators for about £17 so if you have someone similar it shouldn't be too painfull.....

Post by **bmcecosse** » Sun Nov 02, 2008 10:02 pm

Ahhh - 11AC alternator you say - pity you didn't give that information at the start of all this !! As far as I know that alternator has to be wired up with a 4TR unit, and a 6RA relay. They don't have all the gubbins inside like the 16/17/18 ACR units. I think you need to check that out with MGM (surely a Film Co ???) - pretty sure that's where the problem lies! Since the other alternator works fine - the problem IS obviously with that alternator!
Edit - Indeed it does - here's a site I found that explains all http://drcwww.uvt.nl/~%20bogaard/manual/engielec/4.htm

Post by **M_Temple** » Thu Nov 06, 2008 6:21 pm

Went to 'the Alternator man' - great bloke 85 yrs old at Humphreys & Willis in Redhill (recommended to any other 'locals' for any starter/alternator/auto-elec problem). Proper motor factors place with expertise and stock to match.

Turns out it is not an 11AC, but the modern equivalent (LRA100), and it has an integral regulator. However it was kippered - overcharging, showing up to 20v output on his test-bed, and very erratic. He was surprised it hadn't burnt out the bulb in the speedo light, and it explains why the battery volts were as measured.
Replacement new LRA 100 unit £30 + vat. V. reasonable I thought.

Will fit over w/e to confirm, but if no more posts assume the tale has ended.

Post by **bmcecosse** » Thu Nov 06, 2008 9:15 pm

Good - thanks for coming back with the update. I did wonder about the 11AC - they haven't been 'common' for many years now ! That's a good price for a recon alternator, you did well there!

Post by **M_Temple** » Thu Nov 13, 2008 7:16 pm

Just to complete the story - fitted the replacement alternator yesterday and all returned to normal behaviour.

Post by **bmcecosse** » Thu Nov 13, 2008 10:07 pm

Great success!