electrical issues

Thanks to John Weimer, Kimberly, et. al. my 78 is now running again. And it is in the 70's today; last day of extended summer before we really get Fall and lose 20 degrees and get rain. This Board is great !

Of course, every project is two steps forward, one step back. The clock and the courtesy light above the radio and the radio itself no longer work. I do not recognize a fuse for these on the electrical diagram. I have lights, gauges, headlamps, engine. Just these minor items are now out. Is there a fusible link somewhere ? Or fusible wire ?

Also, while investigating the ignition relay and environs during the fix of the original problem, I noticed there is a blue capacitor by the ignition coil. One end seems to be grounded at the strap holding the coil on. The other end goes to a black wire suspended in thin air. Whatever it did (noise suppression?) doesn't seem to affect operation (or if it does I haven't noticed).

And the third point is also another mystery wire. Three wires are coming from the wire bundle that goes to the back of the alternator. There are wires going to the alternator plug itself on the rear of the alternator. These three end in a white block connector. Their color codes are white, white with black stripe, and white with blue stripe. These wires are long enough to rest down by the engine mount. I can't see where they go, if in fact they have ever gone anywhere in the four years I've owned the car. But of course I'm curious.
Again, they don't come from the alternator, they break out of the cable bundle where other wires break out to go to the alternator plug.

Jeff

As the wise and sentient entity and resident ignition Guru, Jeff , kindly pointed out to me in a like situation, that's likely the old distributor trigger wiring, which plugged into the old distributor (the connector reaches the distributor base, n'est pa?).
It doesn't serve any purpose now but to maybe return to original distributor setup someday.
Also, I think the blue nub is (or was) the ignition voltage ballast.

Len

Yup. The connector with the 3 wires went to the 45E dizzy. Not used (at least not on my Pertronix). The blue thing is a noise supression condenser (capacitor).

1) I thought my 78 MGB had the original distributor. Does your comment mean it isn't original, or is that just a leftover connector from an earlier distributor type that was installed on prior models ?

2) Regarding the blue capacitor, since it is noise suppression that is why it doesn't matter. But where would the loose wire go anyway ?

You will have to look to see how your radio is wired. Radios are after market add ons and were wired the way the individual installer wanted to.

The courtesy light and clock are part of the purple circuit.
Find the components on the wiring diagram and trace them back to the fuse. If you have looked at the wiring diagram, you would know that there are no fusible links in the stock loom.

Sorry about the blue-colored noise supression cap, my mistake, not Jeff's.
So I CAN smash it!

Len

jeff great to see some one from hartford in here. if your ever in a jam and need parts stop over. i am in or on the "list"

I am getting used to the symbols schematic you referred me to (I have printed it out in large format in color). More experience with electronic ones versus British automotive ones. I assume by the icon near your member name the electrical things are your expertise. I will check the fuse (terminals 7-8 on the block) which seems to be for all the items that run even when the ignition switch is off. However the problem is now intermittent - sometimes those items are on and sometimes not. So the issue being just as simple as a fuse might not be it. Will know tonight.

dbster Wrote: