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Should the Ignition light stay on while driving

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Should the Ignition light stay on while driving
#1
bugn1967 John May
Kingsville, ON, Canada   CAN
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I was having problems with my Ignition light staying on while the car was off. So I changed the rectifier and regulator. Now it is off while the car is off but stays on the whole time I'm driving(from what I've read it should go off after 800RPM). Also it doesn't seem to be charging. With it running it's at about 12.10V, driving it's at 12.5 if I turn the lights on while driving I get 11.75V and then it goes back to 12.5V when I turn the lights off. I'm I missing something or is the Alt just toast.

Thanks
John

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Re: Should the Ignition light stay on while driving
#2
chanson Avatar
chanson C Hanson
South Florida, FL, USA   USA
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1973 MG MGB
No. That is not normal. It means that you aren't charging the system.

That light is wired to stay on if you are using more electricity than you are producing. Prime suspect is the alternator.

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Re: Should the Ignition light stay on while driving
#3
joron Avatar
joron Silver Member Michel Joron
Roxboro, QC, Canada   CAN
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1977 MG MGB "Victoria"
2018 Jaguar XE "Meghan"
Alternator is not providing enough voltage; the diode/bridge or the brushes are shot, replacement is required I'm afraid.

Go to a place where they sell batteries and they could test the alternator for free; then you know for sure.


1977 MGB Red 'Victoria' and 2018 Jaguar XE 'Meghan'
All Classics:
Married, 2 children, MG MGB May to December, Jaguar the rest of the year.

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Re: Should the Ignition light stay on while driving
#4
tbarker7815 Avatar
tbarker7815 Tom .
Knoxville, TN, USA   USA
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1979 MG MGB Limited Edition (LE)
Should have around 13.8 to 14V when running as I recall. I added a voltmeter to keep a watch on it after my last alternator failed.

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Re: Should the Ignition light stay on while driving
#5
mgguy1976 Avatar
mgguy1976 Michael Keeney
Fleetwood, PA, USA   USA
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1975 MG MGB
Time for an alternator- they can be rebuilt, just had mine done by a local shop, $100.00 with an one year guarantee, or, buy one for around $120.00 or so. Easy swap out.

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Re: Should the Ignition light stay on while driving
#6
bugn1967 John May
Kingsville, ON, Canada   CAN
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So it looks like a Bosch 55amp part #13107 from a 78-80 Ford Fiesta is a perfect match(in case I can't find one for a 1980 MGB) can anyone confirm this.
Sorry maybe I'm looking at the wrong one.

Thanks
John



Edited 1 time(s). Last edit at 2014-07-22 08:39 PM by bugn1967.

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Re: Should the Ignition light stay on while driving
#7
joron Avatar
joron Silver Member Michel Joron
Roxboro, QC, Canada   CAN
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1977 MG MGB "Victoria"
2018 Jaguar XE "Meghan"
The bosch from a ford fiesta was compatible, that was a long time ago. Normally it is just a
Lucas ACR18.

For more details here a list of compatible replacement/solutions:

http://www.britishcarforum.com/bobmuenchausen/17901.html


1977 MGB Red 'Victoria' and 2018 Jaguar XE 'Meghan'
All Classics:
Married, 2 children, MG MGB May to December, Jaguar the rest of the year.

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Re: Should the Ignition light stay on while driving
#8
ohlord Avatar
ohlord Platinum Member Rob C
A tiny Island off the coast of Washington State, N.W., USA   USA
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1957 Land Rover Series I "EYEYIYI"
1957 Land Rover Series I "OVRLND"
1971 MG MGB
1971 MG MGB "Bedouin 2"    & more
http://www.mgccars.com/

plug and play. If your'e not going to do the GM alternator conversion yourself (takes about 20 minutes) this is the way to go.
Your alternator is dead.


LNDRVR4X4.COM
Home of Project "INCARN8'


1957 Series 1 Land Rover electric VEHICLE CONVERSION

FIXITUPCHAP.COM
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RD3 Radar/ Electronic Warfare Technician
VIETNAM 1969-1972

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Re: Should the Ignition light stay on while driving
#9
ozieagle Avatar
ozieagle Gold Member Herb Adler
Geelong Victoria, Australia   AUS
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1958 Wolseley 1500 "Wooly"
1966 MG MGB "Bl**dy B"
1995 Toyota Highlander "Hi Ace Van"
2022 MG ZS
Before rushing off to buy a new alternator, as you've replaced the rectifier and regulator, I would double check you connectors. Maybe it is open circuit and just needs to be repaired.

Herb

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Re: Should the Ignition light stay on while driving
#10
spikemichael Avatar
spikemichael Platinum Member Michael Caputo
Canton, IL, USA   USA
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1973 MG MGB "Freebie"
1973 MG MGB
1974 MG MGB "Spike"
1976 MG MGB "Cecil"    & more
is it bright or just a dim glow?

flipping a diode inline will tell you if it is power going to the harness or harness to the alternator.
Advance Auto has the Lucas orig in their catalog, my local had one on the shelf!

Take a look here for the part numbers and so on:

http://www.mgexp.com/phorum/read.php?1,1526174,1526174#msg-1526174


Michael J. Caputo
'79, '77, '76, '74.5 (rubber dual SU), and '73 owner. Extensive experience in 12v Audio System design and installation. Vendor of Regalia and Promotional Products since 1993. Supplier of Accessories to MOSS. Forum Member since 2009; with a warped sense of humor since birth. Publisher of the annual MGB & GT Calendar, mailed worldwide.


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Re: Should the Ignition light stay on while driving
#11
ingoldsb Avatar
ingoldsb Silver Member Terry Ingoldsby
Calgary, AB, Canada   CAN
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1971 MG MGB
If the lamp is on, it means the alternator is not energized and is not producing electricity. The question is why?

The problem is almost always the rectifier pack - but it can also be due to a fault in the windings of the alternator. If you have checked the connections, and are sure you installed the new rectifier correctly, then you may have a more serious problem and it will be easiest to just replace the alternator.


Terry Ingoldsby
terry.ingoldsby@DCExperts.com

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Re: Should the Ignition light stay on while driving
#12
ErnieY Avatar
ErnieY Ernie Y
Albatera, Alicante, Spain   ESP
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1976 MG MGB GT
Don't forget the brushes too.

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Re: Should the Ignition light stay on while driving
#13
bugn1967 John May
Kingsville, ON, Canada   CAN
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Well I was able to get an old alternator from the person I bought the car from and problem fixed. When running it shows about 13.8V and driving just over 14V and no Ignition light on.
So is it work changing the brushes in the alternator that doesn't work to see if I can get it working right or should I just write if off and buy a new one.

Thanks
John

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Re: Should the Ignition light stay on while driving
#14
ChuckoldNavy53 Avatar
ChuckoldNavy53 Gold Member Chuck Green
Annapolis, MD, USA   USA
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1969 MG MGB MkII "Bee"
Changing the brushes is pretty easy. If you can change the diode stack you can change the brushes. While you are at it, make sure the insulation on the windings is still good and not cracked. This is fairly common on old alternators. It can cause some strange symptoms. Also don't forget to check the bearings on the alternator. As far as replace or rebuild yourself, a lot of it comes down to the cost and the time. Do you have the time available to rework it. For myself I bought a new alternator and then rebuilt the old one myself as a ready spare, when I had the time.
take care;
Chuck

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Re: Should the Ignition light stay on while driving
#15
ingoldsb Avatar
ingoldsb Silver Member Terry Ingoldsby
Calgary, AB, Canada   CAN
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1971 MG MGB
Quote:
Don't forget the brushes too.

When brushes wear they usually cause the light to not come on at all - basically they no longer make contact with the commutator and don't serve as a ground for the warning lamp.

The one exception is when brushes are almost worn out and still touch for part of a revolution. Then they conduct for long enough for the bulb to glow, but not long enough to energize the alternator.

There is also the possibility that you got a bad rectifier or damaged it when you soldered it. Soldering of diodes needs to be done quickly so that they do not overheat.


Terry Ingoldsby
terry.ingoldsby@DCExperts.com

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