Crazy charging voltage

[skids]

When checking charging voltage with a multimeter, I get readings all over the place. I have tried 3 different meters. I have tried two different regulator/rectifiers. I tried 2 external regulators with the stock rectifier hooked-up. The diodes in the rectifier checked out OK in each rectifier using diode setting on meters. The readings are crazy (9, 2, 14, 6, 12, rapidly changing). The rpms do not play into the problem. I have cleaned the connections, including the white wire clip and field coil clips behind the fuse panel. The field coil tests at 3.5 ohms, the stator tests at 0.45 ohms. I checked voltage while running at the field coil clip and it jumps around just like measuring at the battery terminals.

Any ideas? I really don’t want to needlessly add another regulator rectifier to the collection. One other observation. I bought a new multimeter and when it is set to volts and the leads approach the accessory lugs, it registers voltage in the air! Do the erratic readings perhaps come from the dyna coils???

[Bax]

Hi Skids, Not a lot to go on here but when you have your DVM set to VDC the readings usually are erratic in the millivolt range until you touch the leads together, this should be zeroed rather quickly. Have a make and model number of your meter? A pic of your test setup would help as well.

[bikerphil]

I had the same problem with my bike with the Dyna coils, without any suppression, the multimeter goes crazy with the engine running but OK with it off. An analog meter should work OK or try resistor spark plugs.

[skids]

Bax, Three different meters were used, each in the zero to 20 volt DC range. Thanks Phil. I will try resistor plugs and see if it helps. Problem is, the bike is now winterized. Tank and carbs drained and dry. I will try it next spring.

[3Phase]

Sid, does it do it only at idle or at all RPMs? Wandering voltage at idle is usually crusty connections and grounds.

Check the grounds on the frame at the Regulator/Rectifier.

Do a Full Field test by grounding the Green wire to the Black wire (or the frame, if you like) at the R/R harness connector and check the voltage at the battery or the battery bolt on the Starter Relay

There's a test procedure in The Book for the rectifier bridge but it never worked for me; good one checked bad and vice versa... seriously annoying but it's a good way to waste time if you're bored, can't dance and it's too windy to stack BBs.

Make sure the alternator-to-harness plug isn't getting toasty or melted behind the right-hand side cover.

Make sure the wires from the alternator aren't pinched or sliced and diced from $something unpleasant.


(Thinking cap ==ON)

The '78/'79s were the only ones to use the Yellow neutral wire from the alternator to close and latch the Headlight Relay so bypass it to make sure the relay is good or pull it and stash it in the parts pile.


That's about it for now!


Regards,

Scott

[Bax]

Hi Skids, I would expect if you had induced voltage on the leads (in air) this would be suppressed when measuring a voltage at contact points. Guess this will pick up in the Spring when the bike is out of hibernation.

---Bax

[3Phase]

Heh, could be a loose battery cable but that'd be way too easy and no fun to troubleshoot.



Regards,

Scott

(Need to make a sig file)

[bikerphil]

Skids, with your Dyna coils, you are probably running the DW-200 wire kit which are non-suppression. Another option would be to run the DW-600 kit which are noise suppression wires.

[skids]

On 7/19/18 Installed Dyna DC1-1 3ohm coils and bypassed (and removed) ballast resistor. Installed new Dyna plug wires. I don't know what wiring kit I used. I used the one that came with those coils. I can't remember testing charging volts since the conversion to Dynas, but I generally always use the accessory lugs to test non-running battery volts. I am pretty sure that I can just use a set of silicon plug wires and resistor plugs. Gee, I suppose the spark power is going to take a hit but I assume there is plenty to spare. Scott, yes I looked at all of the wiring that I could get to and cleaned clip connectors and battery connectors. I also checked the resistance between the VR and the battery negative (zero). Like I said, I checked the diodes in the bridge rectifier. I wonder if a shorted battery could cause this condition? (I doubt it) It does charge up with a battery maintainer to normal, but bleeds down.

[3Phase]

Hey, Sid, I've run several kind of coils on my my '80G and never had that happen but apparently Phil's seen it with the Dynas sooo... I dunno. (Gallic shrug)

I have a set of 3.0 Ohm Accel Supercoils and they just work with no wandering voltage readings and even with the idle RPMs turned down to a pre-stall lope the voltage never went below battery voltage.

The type of spark plugs or plug wires for the Secondary never made any difference in the Primary voltage on any vehicle I've owned when I checked it with a DVM or analog voltmeter but I'm all-in for learning something new whilst avoiding Dyna-anything if the Secondary plugs and wires mess with the Primary enough to freak out a DVM.

If you have a spare set of stock coils, try them and see if it's the Dynas or a charging system problem?

[bikerphil]

Ok fellas, I just hooked my DVM up to the bike with Dyna Coils. While testing it at different RPM's, the voltage is mostly steady like it should be. I have resistor plugs (BPR6ES) with the DW-200 non-suppression solid core wires on it. Last time I checked it, the meter was unreadable, but I had the BP6ES no resistor plugs in. I'm fairly sure it's the spark interference that causes the DVM issue when running Dyna coils. My other XS has Accel coils (140403's) with Dyna non suppression wires and non resistor plugs. That one is fine with the DVM.

[3Phase]

Thanks, Phil, the RFI from the Dyna Secondaries makes sense!

I've used both and I don't really grok the pining for the non-suppression wires and non-resistor spark plugs thing.

[bikerphil]

Yep, Dyna's are half the price compared to Accel's, so undoubtedly the preferred choice for many of us here.

[3Phase]

Heh, I got my Accel kit in a bucket-o-parts when I bought my '79 Special so the coils and the enormous and ludicrously bright yellow 8mm Accel solid core wires were 'free' or I'd probably have some Dynas too.

I had a pictorial post on dot com about NGK spark plug caps and how they installed the different resistors for variable suppression/non-suppression in the plug caps, maybe something about the wires.
I'll have to see if I can find the posts and restore the pictures for it or make a new post.

[skids]

Hey, Sid, I've run several kind of coils on my my '80G and never had that happen but apparently Phil's seen it with the Dynas sooo... I dunno. (Gallic shrug)

(Snip)
If you have a spare set of stock coils, try them and see if it's the Dynas or a charging system problem?

Scott, the readings change so fast that you can hardly read them while using any of my digital multimeters and at any rpm. This is so when measuring at the accessory lugs, the battery posts, the regulator output. I figured the battery would buffer any variations like that. I do have a buggered set of stock coils I could swap out but with the mods made for the Dynas, I will just go with resistor plugs and see what happens (next spring). The bike is in cold storage till then.