Topic: 77 750 electric issues. Voltage drain

[ryani]

I just recently got my 77 750a to start yesterday!!!!!  It took a little convincing but it fired!  After it warmed up the idle was uncontrollably high and wouldn't come down.  Air leak?   

So today I went out to work on the prob and the battery is dead.  I have 11.5 volts until i turn the key on and then it drops to 8.5v  Parasitic drain i suppose.   I rewired using the ford voltage reg trick found here and the small 3 phase rectifier also found here.

I'm just looking for a good place to start when I start troubleshooting.

Thanks for all the input

[OldSchool_IsCool]

Put the battery on a charger and let it charge fully.  Once charged, let it sit unconnected overnight.  Next day, check to see if your battery has enough charge to start your bike (a simple voltage measurement won't do it, needs to spin the starter).  If it doesn't, then the battery is toast. 

If she does start your bike (or at least spins the motor good 'nuf to start), then leave 'er connected to your bike overnight.  Make sure the key is in your pocket.  If the battery is dead in the morning, then you have a parasitic drain somewhere.

[ryani]

Sounds like a good start.  I got the battery charging on the bench as we speak.  I will pop it back in tomorrow and see if it starts.  If it does run I'll check running voltage also.  The battery is new so I hope I didn't fry it.

[gsnorcal]

If you have a multimeter, you can switch it to DC amps and put the leads between one battery post and the cable from that post (disconnect the cable). This will tell you how much current is being drawn by the parasite. Then you can start removing fuses to see what circuit the draw is on, etc.

Do this with the bike/key OFF. You can blow the small fuse in your meter if large draws are present.

Dave

[ryani]

Thats a good idea.  Thanks!  I have the headlight circuit on a switch right after the breaker so that i've eliminated that as a the problem.  I'm not sure if the led's I put in all the indicator lights would have any affect on my prob.  I'll get the battery charged up and start trouble shooting.

Merry Christmas!

[ryani]

Well I got out to the garage quick.  Didn't spend alot of time because my fingers were freezing.  Anyway I did a quick amp check with the key off and found when I unplugged the voltage reg the amp draw went to 0!  I wired it up as per the instructions but I'll have to do some investigating tomorrow.  Might have to plug the stock one back in and see what that gets me.

[TwoTired]

The voltage regulator drives the alternator (magnetic) field coil.  It is on whenever the battery falls below 12.6V (ish).
As the coil is about 7 ohms, it will draw 1.8 amps whenever the Vreg "thinks" the battery needs charging.  However, with the key switch off, no power should get to the Vreg/Field coil.

If you have points ignition, usually one of the coils is on when the engine isn't turning (again assuming key switch is on.

If you want us to better help your troubleshooting, we will need details of switch positions to make sense of what you are actually measuring.  Further, all modifications to the electrical from stock must be stated.  We only have reference to the stock wiring diagrams.
Custom wiring needs a custom wire diagram, for "outsiders" to analyze.

Cheers,

[ryani]

Got some testing done.  It's not the battery.  Holds a charge.  I did an amp draw off the battery and get .08 amps dc.

I think I found my drain problem.  It has something to do with the ford voltage reg.  When I disconnect it my amp draw falls to 0.  Its back feeding some how.  Maybe a diode in the ignition   (black lead) will take care of it.

Still up for suggestions.  Would going back to the old reg be the easiest remedy.  I would pull my hair out but I don't have any!!

[scottly]

 My guess would be you've got something wired wrong. If the ignition switch is off, there should be no power supplied to the reg, and no drain, at least with a stock reg. Did you add a wire directly from a terminal on the Ford reg to the battery +?

[ryani]

I put the wire from the first terminal on the ford reg to the positive battery terminal.  I still need to check if the ign (black) wire has voltage on it with the key off.

I'll check that tomorrow.

[scottly]

I put the wire from the first terminal on the ford reg to the positive battery terminal. 

That may be your problem. There is no direct connection on a Honda reg to the positive battery terminal. Does the Ford reg have 4 terminals, or three like the Honda?

[ryani]

The ford reg has 4 plus a frame ground connection.  Only three of the wire connections are used.  One for a positive battery connection one wire for the the field (white) wire and one for the ignition (black) wire.  I'll do some checking today. Fired up the furnace in the garage. Letting it warm up as we speak.

[scottly]

I recalled that there was something funky about the four terminal Ford regs from when I wired my Cobra replica, so I hit the books.. (too cold to get much else done; it was 34 inside the shop today!)
Ford used 2 different wiring schemes, depending on whether the car had an idiot light or an ammeter.
The first terminal should be marked I, and have no connection. The second term should be marked A+, connected to battery +. The third, marked S, connected to the black/wht from the ign sw, and the forth, marked F, connected to the white field wire.

[Spanner 1]

With the key 'off' the regulator should not pass voltage to the white wire ( field coil ). See if any voltage on the 'F' term. when the red wire ( A+ ) is connected to the battery. I think the field coil is 'on' all the time =  dead battery PDQ.   Wonder why you took-out the stock reg./rect. ??

[ryani]

Scottly thanks for the info!!  I'll wire it up according to your specs and check for drain.  Might have to wait until sunday though.  It's -4 and we have a wind chill of -25.  Got to love South Dakota winters!!

The reason I needed to use the ford reg was for space. I made the battery/electrics box to fit under the seat.  I cut the reg out of its metal case.  I soldered a wire to it's ground tab for "case" ground.  It's actually very small when it's out of the case.