Rotax 912ULS Rectifier/Regulator

[Flyinglion2000]

Hi, has anyone ever had any issues with their rectifier /regulator on their 912ULS?

 

Mine appears to have given up the ghost. I have checked the alternator and I have 15-17V AC going in, but there is no recorded voltage increase on the output side (measured at the battery terminal on the solenoid) - its a constant 12.4V whihc is only indicating the state of the battery.

 

Ive checked that the rectifier/regulator is earthed, that the 50AMP fuse is not blown, but still the low voltage warning light is lit up and the voltmeter is only readung 12V.

 

Must be the rectifier/regulator?

 

 

[nomadpete]

If you have verified that all crimped connections are low resistance, and the box is well grounded, then it follows that you should have charge coming out. However, the input voltage seems a bit low to me. Unloaded, at 2000rpm or so, you should expect maybe excess of 20volts AC coming from the charge coils. When you replace it, make sure it is located somewhere in airflow as these regulators dissipate quite a lot of power and if they are allowed to get hot it will shorten their life a lot.

 

 

[rick morawski]

Hi, has anyone ever had any issues with their rectifier /regulator on their 912ULS?Must be the rectifier/regulator?

Check also the continuity of the wire from the "C" terminal, which goes to the key switch(check switch connecting) and then to batt +ve, if it's not connecting it won't charge, and if it doesn't disconnect it will discharge the battery. (from memory, wont hurt to check though)

 

Cheers

 

Rick

 

 

[Flyinglion2000]

Thanks Guys

 

Rick, I checked the wiring in my Sav S and to the wiring diagram. My "C" terminal is connected to the voltmeter (white w red stripe wire). My "B" terminal connects (through 50amp fuse) to the starting solenoid terminal whihc connects to the battery +ve.

 

Is that right?

 

 

[Mick]

I've had one go after only about 100 hours.

 

I can't remember the numbers, but it was putting out only what was being used, so while it would run everything, no charge was being put into the battery. Every time we started it took a little more out of the battery that was not getting put back in while running. So after so many starts there would be nothing left - flat battery. Put a charger on it and the battery would come back up fine, but after another X starts would be too low to start.

 

After replacing it we took all of the resin out of the back to expose the circuit board and found a dodgy solder joint.

 

 

[Kyle Communications]

Did you fit the 22,000 uF capacitor that is"recommended" to the wiring?. If you do not fit this is you happen to shut the engine down with the master switch and NOT the mag switches first it will toast your regulator.

 

 

[Kyle Communications]

It is in the rotax manual…BUT NOT SUPPLIED

 

 

[rick morawski]

Thanks GuysRick, I checked the wiring in my Sav S and to the wiring diagram. My "C" terminal is connected to the voltmeter (white w red stripe wire). My "B" terminal connects (through 50amp fuse) to the starting solenoid terminal whihc connects to the battery +ve.

 

Is that right?

Yes it's right, it gets disconnected from +ve by the R lead thru the switch. I agree with the others, that it is cooked. Order one from Floods and get a capacitor if you don't have one. Also be aware you can damage the sprague clutch if you try to start up with an under charged battery, so charge your battery up before starting.

 

 

[Flyinglion2000]

Well I checked all the wiring again and it looks fine.

 

Restarted and everything works - charging at 14v low voltage light out. Went for a hours flight no problems.

 

Next day not so good - low volt light on and no charge to battery (as indicated on plane voltmeter).

 

Grrr.

 

So will check all wiring again..

 

any other suggestions before I send the regulator off to Floods?

 

Mark - no I did not see the Rotax recommendation for the capacitor. Did you also instal one for your fuel pump like they suggest?

 

Where can I buy these (and brand soec etc) from around Brisbane or is it best to shop online?

 

Cheers

 

 

[cscotthendry]

Well I checked all the wiring again and it looks fine.Restarted and everything works - charging at 14v low voltage light out. Went for a hours flight no problems.

 

Next day not so good - low volt light on and no charge to battery (as indicated on plane voltmeter).

 

Grrr.

 

So will check all wiring again..

 

any other suggestions before I send the regulator off to Floods?

 

Mark - no I did not see the Rotax recommendation for the capacitor. Did you also instal one for your fuel pump like they suggest?

 

Where can I buy these (and brand soec etc) from around Brisbane or is it best to shop online?

 

Cheers

Hi:

The Rotax manual specifies a capacitor of at least 22,000 uF with a 25V rating. You can source these from RS components

 

http://australia.rs-online.com/web/p/aluminium-capacitors/3818999/

 

You'll also have to buy a mount for it

 

You could probably also source one directly from Bert Floods.

 

BTW, The reccomendation for the capacitor is on Pg 7 of the Rotax engine installation manual. You can download the pdf from Rotax, or Rotax Owner

 

BTW, the capacitor should be connected to the regulator such that it cannot be disconnected even when the main switch is off.

 

HTH

 

 

[Kyle Communications]

Scott has taken care of it…I get them from RS or element 14…I have a couple here and bases I keep for the local guys I usually just sell them at cost especially if you fly a Savannah

 

 

[Flyinglion2000]

Thanks Scott, Mark and everyone.

 

I will go to RS at Archerfield on Monday on my way to work.

 

I am thinking the problem may be with the connectors to the regulator, on close inspection of the male tabs on the regulator I can see evidence of arcing on one of the male tabs that connects to the alternator.

 

cheers

 

 

[Flyinglion2000]

Ok I now have the capacitor but not being an electronics person I don't know how to wire it in.

 

From the Rotax manual one pin of the capacitor is earthed / grounded but the other pin is wired to ???? Any photos if possible greatly appreciated.

 

Also why was a 50amp fuse supplied but the manual suggests says 25amp fuse?

 

Cheers

 

 

[cscotthendry]

Ok I now have the capacitor but not being an electronics person I don't know how to wire it in.From the Rotax manual one pin of the capacitor is earthed / grounded but the other pin is wired to ???? Any photos if possible greatly appreciated.

 

Also why was a 50amp fuse supplied but the manual suggests says 25amp fuse?

 

Cheers

How you wire in the capacitor depends a bit on how your aircraft is wired. Some aircraft have a master switch that carries all the current from the charging system to everything else. Some have a relay that does that and the master switch only activates the relay. If you have a wiring diagram for your airplane you should be able to see where the connection from the regulator goes to the the element that controls the master current. In the Rotax manual, they show the R, B+ and C pins of the regulator connected together and that joined connection is the "output of the regulator to the system. If you have something like that, then that is the point where the + terminal of the capacitor should connect. The - terminal of the capacitor should connect directly to the common ground bus on your aircraft NOT just to the frame of the aircraft.

I've attached a diagram from the Rotax manual and the capacitor is number 14 in the diagram. The important thing is that the capacitor is connected directly to the output of the regulator before the output switching. The other important part is that the - connection of the capacitor should be connected to the common ground bus on your aircraft, NOT the fuselage.

 

To do this, you might have to do some detective work through the wiring. I haven't attached a pic of my setup because my reg is forward of the firewall and the capacitor is on the back of the firewall inside the cockpit. My setup probably wouldn't relate to how your plane is wired anyway.

 

I wired my plane with a relay as the master switching unit and my "master" switch just controls the relay. I did this because it is cheaper to buy a 30 amp relay than a 30 amp switch. Also, that is how it is shown in the Rotax diagram. On that diagram, the relay is item 19 and the master switch is item 16. If you have a heavy current master switch instead of a relay, then the output wire from the regulator will go directly to one side of that switch instead.

 

In my case, the wire from the regulator goes to the + side of my capacitor, and another wire goes from the + side of the capacitor to my master relay.

 

HTH. PM me if you get stuck and we'll delve further into it.

 

 

 

[Kyle Communications]

Everyone usually mounts the cap on the strip that goes across the firewall that the top of the nose leg attaches to just in front of the reg the cap from memory goes direct to the reg connection

 

 

[Kyle Communications]

goes to R and B+ usually you want it not far from the regulator or of course if it is easier to the input side of the fuse. My main battery earth goes to the base of the solenoid then off to the motor the cap earth goes under that same bolt for both earths

 

 

[Kyle Communications]

You can see mine here just in front of the reg and beside the starter solenoid

 

 

 

[Kyle Communications]

Has anyone out there got a 4 wire and or a 6 wire with soft start that do not work anymore and want to donate them so I can make a better new improved much much cheaper version that will be almost bullet proof ?. I have the 6 wire one all stripped but need the 4 and the 6 with the soft start as I want to make 1 unit only that does all versions of the ignition module...it makes more sense to just make 1 unit that can be wired differently between different engine versions

 

Mark

 

 

[IBob]

How you wire in the capacitor depends a bit on how your aircraft is wired. Some aircraft have a master switch that carries all the current from the charging system to everything else. Some have a relay that does that and the master switch only activates the relay. If you have a wiring diagram for your airplane you should be able to see where the connection from the regulator goes to the the element that controls the master current. In the Rotax manual, they show the R, B+ and C pins of the regulator connected together and that joined connection is the "output of the regulator to the system. If you have something like that, then that is the point where the + terminal of the capacitor should connect. The - terminal of the capacitor should connect directly to the common ground bus on your aircraft NOT just to the frame of the aircraft.

 

I've attached a diagram from the Rotax manual and the capacitor is number 14 in the diagram. The important thing is that the capacitor is connected directly to the output of the regulator before the output switching. The other important part is that the - connection of the capacitor should be connected to the common ground bus on your aircraft, NOT the fuselage.

 

To do this, you might have to do some detective work through the wiring. I haven't attached a pic of my setup because my reg is forward of the firewall and the capacitor is on the back of the firewall inside the cockpit. My setup probably wouldn't relate to how your plane is wired anyway.

 

I wired my plane with a relay as the master switching unit and my "master" switch just controls the relay. I did this because it is cheaper to buy a 30 amp relay than a 30 amp switch. Also, that is how it is shown in the Rotax diagram. On that diagram, the relay is item 19 and the master switch is item 16. If you have a heavy current master switch instead of a relay, then the output wire from the regulator will go directly to one side of that switch instead.

 

In my case, the wire from the regulator goes to the + side of my capacitor, and another wire goes from the + side of the capacitor to my master relay.

 

HTH. PM me if you get stuck and we'll delve further into it.

 

[ATTACH]18669[/ATTACH]

Just lighting up the electrics in the Sav build here:

 

The Sav wiring diagram shows the regulator B output connected to one side of the starter relay (*), and from there to the battery +

 

This is the only connection to the battery +

 

Regulator R goes to the master switch.

 

Regulator C goes to the Low Fuel Indicator, also the Charge Indicator light.

 

I have connected my capacitor between (*) which is regulator B and battery plus......and the battery negative cable I ran.

 

On connecting the battery, I initially get a spark at the battery terminals: this makes sense as the capacitor is permanantly in circuit with the battery, and is receiving an initial charge.

 

Is this correct? Should the capacitor be permanently across the battery???

 

 

[facthunter]

Why not . If you have two batteries in parallel each is across the other. Nev

 

 

[IBob]

I'm trying to understand the intention, Facthunter.

 

The diagram shown by cscotthendry above shows a situation where the output of the regulator may be isolated from the battery 20 if the relay/switch 19 is opened. I'm not sure how this then risks blowing the regulator, but the capacitor as shown there would act to smooth the output voltage and current drawoff while 19 was opening.

 

In the Savannah, however (and assuming the circuit diagrams are correct), the output of the regulator is permanently wired to the battery+

 

So turning off the master switch while running will remove the load of the various instruments, lights etc, but the battery will remain in circuit with the regulator.

 

Why not leave it in circuit? Capacitors do fail. And I suppose it's instinctive to want to have everything isolated when you turn the power off...

 

 

[facthunter]

Yes the only time it's totally safe is when all sources of electrical power are removed from ALL the circuitry.. This includes all batteries and any operating generator/alternators (engine running) and charged condensers. Batteries and condensers can fail internally but we can't do much about that once it's installed. I consider the condenser to be pretty much like a battery but holding a lot less energy in it's own right , but is a risk in a live circuit, (as you say). Condensers usually fail in a transitory voltage overload or leakage /heat situation. Batteries are becoming more dangerous with more critical charging regimes for newer offerings, in all kinds of applications. and probably more of a risk than a good quality condenser .Nev

 

 

[Downunder]

Not sure if this is a help. Shows capacitor connected to "C" and earth.

 

And 40 V capacitors are much better than the 25v....

 

[/url]http://pointsforpilots.blogspot.com/2012/12/testing-rotax-912914-generator-and.html

 

 

[IBob]

Thank you Downunder. That's a really nice write-up too!

 

I've done some searching/reading of other sites and threads, and the principal intention (as stated here and elsewhere) does seem to be to protect the regulator from sudden loss of smoothing/load if the battery is disconnected from the regulator while the engine is still running.

 

The Savannah is wired in such a way that the battery is permanently connected to the regulator, so this would seem to be less of an issue.

 

(NB: see Below)

 

However a secondary issue is the amount of noise/ripple at the regulator output, and the effect this may have on avionics etc. Once again, having the battery in circuit goes some way towards smoothing this out, but since the battery in the Savannah and many aircraft is some distance from the regulator, a capacitor at the regulator will provide improved smoothing. On that basis, I will install the capacitor.

 

ideally the

 

As noted here and elsewhere 22000uF 25V is a very skinny minimum spec. 40V or higher is less likely to fail. And ideally the capacitor should have a high temperature rating too: that hadn't occurred to me when I ordered my capacitor.

 

And NB: Below

 

Lots of pics show the regulator with C, B+ and R outputs jumpered together. This obviously works fine BUT:

 

IF the aircraft is to be wired so that the battery is permanently connected to the regulator (as the Sav is), it looks as though these outputs have to be wired separately, otherwise the battery will discharge through C when the engine is not running.

 

I haven't followed this through, this is just from the odd comments I picked up from other threads.

 

In the Sav, B+ is wired to the starter solenoid and the battery only, R is wired to the master control switch, which then feeds the instrumentation etc. And C goes only to the Voltmeter and the Charge Indicator.

 

 

[merc]

" AeroElectric Connection" by Bob Nuckolls is an excellent reference.

 

Thank you Downunder. That's a really nice write-up too!

 

I've done some searching/reading of other sites and threads, and the principal intention (as stated here and elsewhere) does seem to be to protect the regulator from sudden loss of smoothing/load if the battery is disconnected from the regulator while the engine is still running.

 

The Savannah is wired in such a way that the battery is permanently connected to the regulator, so this would seem to be less of an issue.

 

(NB: see Below)

 

However a secondary issue is the amount of noise/ripple at the regulator output, and the effect this may have on avionics etc. Once again, having the battery in circuit goes some way towards smoothing this out, but since the battery in the Savannah and many aircraft is some distance from the regulator, a capacitor at the regulator will provide improved smoothing. On that basis, I will install the capacitor.

 

ideally the

 

As noted here and elsewhere 22000uF 25V is a very skinny minimum spec. 40V or higher is less likely to fail. And ideally the capacitor should have a high temperature rating too: that hadn't occurred to me when I ordered my capacitor.

 

And NB: Below

 

Lots of pics show the regulator with C, B+ and R outputs jumpered together. This obviously works fine BUT:

 

IF the aircraft is to be wired so that the battery is permanently connected to the regulator (as the Sav is), it looks as though these outputs have to be wired separately, otherwise the battery will discharge through C when the engine is not running.

 

I haven't followed this through, this is just from the odd comments I picked up from other threads.

 

In the Sav, B+ is wired to the starter solenoid and the battery only, R is wired to the master control switch, which then feeds the instrumentation etc. And C goes only to the Voltmeter and the Charge Indicator.

" AeroElectric Connection " by Bob Nuckolls is an excellent reference for wiring aircraft, a must have if your building.

 

Also Google "Matronics E mail list and go to the AeroElectric forum for every wiring question you ever thought of and plenty that never entered you head.