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Charging Problem - alternator conversion

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AlamedaMGB

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OK, so my 77 B died on the freeway.. just plum ran out of juice for the fuel pump.. but no charge light!!

Sigh.. so I took apart the dash and found that the charge light has an intermitent connection in the socket.. Are there any replacements? Has anyone looked into a replacement socket? Does the charge light circuit have a resistor across it in 77 so that the alternator can get excited?

the light has never come on in the past, so I'm not surprised... Now that I've got the ligh working, it wants to stay on most of the time, so I guess it's time for a new alternator.. Should I go with a lucas replacement..

Anyone here have an experience with the Fiesta alternator swap, or the Saturn swap? I am looking for any personal experience or opinions.

Thanks in advance.

Jeff
 
Fiesta swap is almost a bolt-in swap... minor filing of the alternator housing to make it bolt in. Some people have mentioned possibility of needing a spacer to move the alternator up about a 1/4" to keep the belt lined up with the other pullies... nothin difficult mind you. Porbably the toughest part is the wiring, but that's not hard to do either. I apparently got ahold of a bad refurbish Fiesta alternator or I'd be using one right now. Fortunately, my Lucas is still good.

All your electrical connections between the alternator and the battery good and clean? If I'm not mistaken, the charge light will be lit if battery is low or if the alternator is putting out low power. Best to check both and ensure the connections between the two are solid.
 
For goodness sake take the alternator some place and have it checked before you go further. They free to check and cheep to fix.
 
You might already know this, but the 'ignition' light only comes on when a voltage difference exists between the alternator output and the battery output. Turning the key to the 'run' position will cause this on startup, for example.

Any auto parts store (Advance Auto, Autozone, et al) would have an alternator tester and would test it for free. It can tell you within a couple of minutes if your alternator is on it's way out.

Also, check that your drive belt has the proper tension; a slack fan belt would cause the alternator to not deliver a proper charge, thus setting the ignition light on. Don't get it too tight, or you'll wear out your alternator/water pump bearings quickly. I believe the proper tension is 1/2" in the longest run between two pulleys.

Try those two things before you shell out for a new alternator. Hope this helps.
 
...But in the MGB charging system I know...


If the connection to the light isn't working, Then the alternator will NOT get that initial bit of voltage needed to start charging. IE: If the light is blown or not connected correctly, The alternator will not start charging.
 
Thanks for the replies..

I should have stated earlier that I am sure it's the alternator and have diagnosed it by trying to excite it directly with jumpers.. I used to work in the auto industry and would never trust my lucas alternator to the part time employess at the local Kragen to connect ANYTHING to my alternator ( seen too many fried, and far more tested as 'bad' when they were not )


Checked the tension when I noticed and replaced a bad water pump. THat's OK.

I haven't checked the connections at the battery, I'll check that as part of the drill.

I'm still concerned with the charge light socket, as the light is very touchy with the key in the on position..

Thanks again
 
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