Yes, Zeftronics seem to be recommended regardless of plane brand. The Mooney crowd loves them too.
I was unable to find the exact issue so far.
I think the best thing to do is to replace everything, since they would need replacement anyway sooner or later.
Is the Zeftronics the best choice as a voltage regulator? I wasn’t able to find the exact model for a G1 TB20, 14V.
I am sure after 40 years there must be more robust and modern units out there to replace the original parts. Any suggestion for alternator, voltage regulator, filter, etc. would be greatly appreciated.
If it helps, my plane is low tech. I just have an amperemeter. As I had an alternator failure in the past, I have the habit to look carefully at the indicator. Because of the very low consumption during flight (low tech I said) the pin is really near 0.
But just after starting the engine, as you just draw on the battery, pin goes frankly on positive way. This summer, I was surprised, when I switched on the alternator, the pin stay several minutes before moving (like it need to warm) but after that it worked. I flew nearly 5 months with this phenomena. (Never accept strange things in aviation) during a flight the pin was moving from + to 0… a bit like you and finally definitely to 0. I came back without alternator (I already did it).
The trick was a bad connection to the regulator…. since that time I have also a car tension indicator as a 12v plug. With this plug I can read the voltage to confirm charging is ok.
In your case such easy 12v socket lighter plug can help you to understand if it is becoming from your EDM or not. If not, bad connections can be on alternator or regulator.
Hope you will find
CPA (Cessna Pilots Association) recommends Zeftronics as being heads and shoulders above OEM regulators/ACUs, and strongly recommends using them whenever replacing a regulator. I’ve had one on my C172 for ages and they are very reliable. They make models for most SE GA aircraft, but I don’t know if Socata is on the list. Type in the p/n from the TB20 parts catalog and see if something comes back.
I have posted this a while back before the Covid madness started and forgot to press the ‘watch thread’ button… Sorry for this, maybe @Peter can move it there.
A lot of answers received and I will probably start by disconnecting the ALT breaker and measure the cables’ resistance, then measure voltage with a multimeter in various places to confirm the EDM readings… maybe a simple contact spray will solve an erroneous reading.
As @Airborne_Again noticed, there seems to be a relation between voltage and current (when one goes up the other goes down), is this a clear indication something must be wrong with the voltage regulator?
I’ve read the alternator is most probably an old 60s design for cars and Peter said the regulator should be a Lamar PWM. Most probably I would want to replace these anyway. Are the any new, alternate parts on the market?
A modern, solid state version regulator 10 times better and an alternator half the size of the original must already have appeared by now for sure…
AlexTB20 wrote:
The values are all over the place, and I don’t even know where to begin to find the cause.Can it be a battery issue? Or maybe the alternator or something wrong with a regulator somewhere? The engine starts normally and I cannot see any other abnormal behavior on the 5 years old battery.
It looks like the voltage is going down when the current is going up and vice versa. I suspect a problem with the voltage regulator.
I have some voltage/amperage indication issues on an EDM930 primary engine monitor, installed on a Socata TB20.
The values are all over the place, and I don’t even know where to begin to find the cause.
Can it be a battery issue? Or maybe the alternator or something wrong with a regulator somewhere? The engine starts normally and I cannot see any other abnormal behavior on the 5 years old battery.
It’s true I have added a lot of consumers on the avionics bus lately, on a system that maybe wasn’t designed for so many instruments.
Good. The Lamarsaurus is very susceptible to field resistance and the Hartzell troubleshooting chart will be useful, but I agree there is some weird de-phasing between current and voltage, if you are indeed measuring bus voltage.
In a TB20 (which is the type shown in the OP’s profile) they use a solid state Lamar regulator which PWM modulates the field current.
The ammeter displays the current going into or out of the battery (excluding starter motor current, for obvious reasons).
Peter wrote:
What concerns me is that the voltage goes down when the current goes up
This behaviour depends on where in the circuit you are measuring amps.
An oscillating voltage regulator is frequently caused by high resistance in the field wiring/connectors. A few sprays with contact cleaner and dis/re-connecting sometimes helps.
In your airplane this wiring probably goes from the Alt Field breaker to the ALT switch to the VR to the alternator.
Any resistance higher than a few ohms is cause for concern. If you can close the ALT switch with BAT off (some aircraft cannot), then measuring from breaker input (accessible in your airplane?) to VR input will factor ALT switch, breaker and associated connectors in one single measurement.
An alternate way is measuring voltage at the VR field input and output with engine stopped and BAT+ALT on (it should be max 0.5V less than bus voltage).
You can follow Hartzell’s troubleshooting flowchart assuming no/low ALT output and this will take you the long way down to the bottom of the chart. Further guidance here
