Alt Field switch squawk

Webb · #1 11-09-2008, 02:48 AM

N32WW had it's maiden flight yesterday. Taking care of a few squawks and I have one that doesn't make sense to me. It is on the alt field.

Open alt field switch (off position)- alternator charges. Closed alt field switch (on position) - no alternator charge.

Here's where my confusion is coming in. The switch is a 5 amp circuit breaker. It is the same style and type as all my light switches. It is installed in the same orientation that my other circuit breaker switches that work correctly. It would be a major PITA to flip it since one of the terminals that is slanted is connected to the buss bar. The other terminal goes to the master switch. When closed (on position) the master switch properly closes the master solenoid.

In summary, closing the circuit turns off the ALT FIELD. Leave it open, the alternator puts out. What gives?

noelf · #2 11-09-2008, 04:51 AM

Congratulations on your first flight!!

I agree, your ALT switch issue does seem strange. Here is what I would do first. Remove the field wire at the alternator, turn on the Master sw, and with a voltmeter attached to the disconnected Field wire (at the alternator end), see if +12V is present when the ALT FLD switch is on, and not present when turned off.

Hopefully, this will point towards the switch/CB or the alternator as the misbehavin component. And, if it turns out to be the switch, you get to verify that it is really installed in the desired orientation.

Again, CONGRATULATIONS!!...

dhall_polo · #3 11-09-2008, 06:34 AM

Put pancakes at EAA690@KLZU on your post-phase1 agenda! First Saturday morning every month...

Mark Burns · #4 11-09-2008, 06:53 AM

Quote:

Originally Posted by Webb

N32WW had it's maiden flight yesterday. Taking care of a few squawks and I have one that doesn't make sense to me. It is on the alt field.

Open alt field switch (off position)- alternator charges. Closed alt field switch (on position) - no alternator charge.

Here's where my confusion is coming in. The switch is a 5 amp circuit breaker. It is the same style and type as all my light switches. It is installed in the same orientation that my other circuit breaker switches that work correctly. It would be a major PITA to flip it since one of the terminals that is slanted is connected to the buss bar. The other terminal goes to the master switch. When closed (on position) the master switch properly closes the master solenoid.

In summary, closing the circuit turns off the ALT FIELD. Leave it open, the alternator puts out. What gives?

Hi Webb,
Most master relays (solenoid) are wired in such a way thet you ground one terminal to make it energize. That way the wire feeding the master switch is not hot. It's a little early in the morning for me to think about what may be happening, but think about what I said as to how the master switch works.

Mark

Webb · #5 11-09-2008, 08:23 AM

Quote:

Originally Posted by noelf

Congratulations on your first flight!!

I agree, your ALT switch issue does seem strange. Here is what I would do first. Remove the field wire at the alternator, turn on the Master sw, and with a voltmeter attached to the disconnected Field wire (at the alternator end), see if +12V is present when the ALT FLD switch is on, and not present when turned off.

Hopefully, this will point towards the switch/CB or the alternator as the misbehavin component. And, if it turns out to be the switch, you get to verify that it is really installed in the desired orientation.

Again, CONGRATULATIONS!!...

Thanks,

When I first engerized my panel, The master switch worked fine but was upside down. I rotated it so it would be off in the down position. This means the jumper from the alt field is now reversed on the switch position. I'm beginning to believe that may be it.

This picture is before installing the panel. The alt field breaker switch is just left of the master switch and the master switch had not been rotated.

I don't think it can be the orientation of the alt field switch. Since it is a circuit breaker, and same make as the light switches, I don't think I could mess that one up since the others are wired correctly. In the picture below, the left 4 are strobes, nav, taxi, and landing lights.

Somehow I think it is tied to the master switch in some way.

Worst case - I put a label on it for the backwards position for the time being but would rather fix it than live with it.

noelf · #6 11-09-2008, 09:09 AM

Putting a backwards "label" on the Alt Field switch...well, I wouldn't do it. If you think it is wired correctly, then you should understand why it works backwards first before changing the labels. At this point, something does not seem right.

From your picture post, I could not figure out which switches you were talking about. Can you describe again using the big round OFF Mag L/R Start keyed switch as a reference? I was looking to see how many wires went to each switch. The MASTER SW position (dependent on your wiring philosophy) has two wires, a B+ hot side on the input, and the other side of the switch would go to the Master Solenoid (relay). When energized, this solenoid supplies power to the voltage distribution bus, and B+ should appear to the "input" side of the Field Switch.

Turn on the field sw, and B+ voltage should pass through this switch and appear at the alternator field terminal.

If your design is other than Van's internal regulator unit, or if you have included an "essential bus", there may be some differences in the overall scheme, but the basic idea of getting the field voltage to the alternator is the same.

Also, I am assuming that you are using the individual units with combined function switch/ circuit breakers, and not the red split rocker sw (ala Cessna) in the master / alt circuits.

noelf · #7 11-09-2008, 09:18 AM

OOPS!! My BAD!!

The battery side of the Master Solenoid is always HOT. Internal to the Solenoid is the circuitry that activates the solenoid when a ground is applied to the control terminal of the solenoid.

This ground comes from the Master Switch. So, one side of the master switch is wired to the solenoid, and the other side of the switch should go to ground.

Sorry for the misinformation in my previous post...

Webb · #8 11-09-2008, 09:37 AM

I figured it out. Went to the spare parts box and pulled out a 5 amp switch breaker. Notice the white letters on the bottom of the alt field switch and the light switches don't.

Letters are on the load side. I've got that switch upside down.

Any mystery solved. 2 hours of ponderment, 5 minutes of fixing.

Thanks everyone.