Extraneous Appendage

2011/02/25

 

The Rans wiring diagram, while it has been updated over the years, continues to include a fuse on the regulator that is not specified by Rotax.

Here is how Rans suggests you wire the regulator:†††† RANS

 

Note the two fuses that Rans highlights with** directing you to see the Rotax diagram for the size of the fuses. One is on the C line between the regulator and the master bus; the other is on the combinedR and Blines before they connect to the battery +ve at the starter solenoid.

 

Here is a panel that followed this diagram. You can see thethe two big breakers on the lower right:

 

Now take a look at the Rotax diagram that Rans suggests you go to.This is how Rotax suggests you wire their regulator:††† Rotax

 

Rotax does not have the two fuses. It has one 25 amp fuse on the main power output from the regulator (the R and B).

 

You can see that the two middle power output wires (R and B) are joined up with the outer C sense line prior to going into the single power output fuse. This C line does not flow any current. Its purpose is to simply read the voltage in the system. Since the other side of the fuse eventually goes to the battery, the C line gets the voltage it needs and the power output of the two middle wires gets to the system through the fuse. Notice that the power goes directly to the main bus without passing through a switch. The power coming from the battery is switched.

 

Here is a simplified version of the Rotax diagram. I include a 25 amp fuse on the battery output so that the #10 lead going forward to the main bus is fused.

My Wiring

In my last installation I did not fuse the power to the starter switch. Master and starter switches were mounted beside the rear seat. Also did not include the battery disconnect.

 

The resetting automotive fuses I use are handy in that they come with mounting tabs and 8-32 posts for wire connectors (and they are a lot cheaper than the breakers shown above). This makes it easy to hook up the R, B, C, Capacitor and power to the indicator lamp all on one post on one side of the fuse and the cable to the master bus on the other.Here is a picture of one:

 

From the regulator connector, the two red are the R and B, green is C and white is L. The white L line goes down then off the right side to the lamp; the the second white line on the right from the lamp connects up with the green at the fuse. The other side of the fuse goes to the master bus which is on the other side of the plate.

 

Because Rans puts the starter solenoid with its 12V supply near the regulator on the firewall, it is convenient to dump the regulator output there and have it permanently connected to the battery. You can see, however, that Rotax does not do it this way. Rotax has a direct connection to the master bus and the battery power through a switch to the bus.

 

The other difference I have with the Rans wiring is that it would appear that they use the voltage on the Lamp, L line to drive the hour meter. I donít know if it could do both but my preference is to wire in the charging indicator lamp as per Rotax because it is a very useful device in that it shows when the system is charging and if you have left the master on after shutdown.

 

I am not an electronics guru, so if someone can spell out why Rans deviates from what Rotax suggests and puts in the additional fuse, I would greatly appreciate it but until I hear otherwise I will continue to leave this guy out and wire as per Rotax.

 

pcowan41at bell dot net