Alternator Ripple Test Help

The car in question is a rally car with bespoke wiring. It is an old school car so no OBDII. It runs a Davies Craig electric water pump & fan with associated electronic controller.

I noticed the DC electronic controller flashing random lights on it which meant it wasn't happy about something. Also, the relay for the engine fan (that it controls) was clicking rapidly at times.

To investigate I decided to take a close look at the alternator. I hooked up my Picoscope to the alternator BAT+ and alternator chassis (ground). At idle with minimal load on the alternator, battery fully charged I got this picture;




A very ugly picture me thought. I had a spare regulator for the alternator so I installed it and tried again. I got this picture;




Although it looks better it is still ugly. I can pick out repetitive peks and troughs but I still have the major spikes and the sharp negative peaks indicated by the green arrow.

I then decided to measure the alternator current, with car lights on, using the 600amp probe and got this;




I am not sure what to make of this. It appears to be clean and repetitive but the sharp peaks worry me. I was expecting a more rounded profile.

Can anybody with the necessary skills tell me what I am looking at please????? I am starting to think that I DO NOT have an alternator issue but I cannot explain the spikes I am getting in the voltage pictures. Maybe the diodes are now OK due to the regulator replacement but maybe one or more of the windings are faulty (new alternator required)??

As a final check, I decided to connect the scope to the fuse that feeds the Davies Craig controller (I guess I could have used any live wire in the system to get the same picture). This is what I got;




To be honest this horrifies me. 16v peaks!!! I am not sure if these spikes relate to the AC spikes from the first picture but regardless, the controller would not be happy!

Although my scope is a great tool I am finding that I am constantly asking questions beyond my knowledge. I love to learn but currently I am constantly trying to catch up!!!!! Heeeelp.

This a "normal" alternator voltage ripple pattern from a Denso alternator on a high mileage tin top.
The spike on it is from an ignition firing event.

In this case voltage spikes are from ignition firing events.
You could try to suppress the interference from the water pump motor with a capacitor between the + and - terminals wrong but I suspect something with the pump motor such as worn brushes.
That is is the limit of my knowledge on these pumps which I must confess as an former club racer from the old school I am more than a little bit cynical about.

Thanks for the input Andy.

What are looking at to think there is intererence from the water pump motor? The spikes on the last picture?

My ripple test post regulator replacement picture has big spikes. These you would say are from the ignition system??? Take those out and maybe it looks much more normal and correct?

I should have also said fit a suppressor to the alternator to the alternator to filter out the spikes that are synchronized with the alternator ripple.

I agree with Andy about the spikes, definitely ignition interference. This is very easy to see while you're scoping stuff under the hood, especially unshielded circuits. Without the spikes, those waveforms look pretty normal.

How many wires are connected to this electric controller? Mostly thinking about monitoring power/ground at the controller during the light flashing, OR monitoring the relay control side during the rapid switching.

I replaced the alternator and the ripple test looked great. Very few spikes and what were there were much smaller peak to peak. I tested the quality of the 12v feed (14.2v actually) and it was lovely and clean. Very happy.

Looks like those horrible peaks were not ingition related but something to do with the poor condition of the alternator.