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Any Skyview users actually crank your engine yet? Problem...

Bill_H

Bill_H

Well Known Member
For full details/diagnostics of the problem, see here, just posted:
http://www.vansairforce.com/community/showthread.php?t=82782&page=14

The short version is I cranked my engine for the 1st time today. It cranked for 4 SECONDS then stopped. (This was NOT a starting test - bottom plugs were out, no fuel, no ignition.) The AV-50000A power distribution box normally has a fan running full time when the master is on, it stopped when the cranking stopped ad has not come on since with several power cycles. Most (not all) of the other electrical systems have continued to work fine.

This may have been the first non-Van's cranking test using the new avionics and this box power distribution box. Please indicate if you have cranked! 3-25-12

On the plus side, my fuel system pump rate and leak tests went just great!

Bill H.
 
Bill it sounds like you and I are on the same page. I started mine yesterday. It went OK no issues as you describe. The only issue I have is the installation seams noisy. I don't like the way the prop feels when I just pull it thru. Sounds like rubbing in gear case. It does seem to work fine. I may just have to get used to it.
I am still having audio issues. The intercom does not work and I can just barely hear com radio. Nothing on music in or anything else. I got 5.1 followed hook up but did not need extensions.
On my way to FL maybe I will get some answers there.
 
I have found when there is a 50/50 chance to do something right, 80% of the time I get it wrong. Audio issue fixed.
 
What was your solution? My intercom (on first, quick test) is "squealy." But I am not bothering to get all of the pots adjusted until I find out if I am getting a replacement AV-50000A. The Skyview voice does come through the intercom so it is prewired for that!
 
PROBLEM SOLVED - We think it was just a "weak" 2A fuse in the starter circuit. After replacing that fuse, several engine cranks with no further problems. Bill H.
 
Bill I just had some wires in the wrong place. Looking at connector backward. Got to follow those directions.
 
Blew another 2A starter circuit fuse today. Working with Vans on checking the starter relay circuit. On a trip, will take a few days.

Any other reports of this phenomena welcome.

Question for existing RV-12s - I imagine the starter circuit is identical EXCEPT that the new Skyview Van's AV-50000A power module box has an internal fan that is also powered by this 2A starter circuit. Did the prior (D-180/100) power distribution system have a fan? (I do NOT mean the two fans in the panel base powered on the fuel pump circuit. I mean in addition to that.)
 
Did the prior (D-180/100) power distribution system have a fan?
Click to expand...
No, there are no fans on the 2amp starter circuit of the original avionics package.
There are two major causes of fuses blowing: short circuit and overload. As part of the troubleshooting procedure, I would temporarily replace the 2amp fuse with a 3 amp fuse. If the 3 amp fuse blows, then I would suspect an intermittent short circuit. If the 3 amp fuse does not blow, then that would indicate an overload condition was blowing the 2 amp fuse.
Fuses are sized to protect the wires, not the load. Even 22awg wire is able to safely carry 3 amps.
Perhaps the normal load is high enough to intermittently blow a 2 amp fuse.
Joe Gores
 
Van's is putting together some troubleshooting tips for me for when I get back. They think the starter relay should only be taking about 0.5 amps on the switch side.

From my understanding, normally a Rotax starts up within a second or two. I've been doing longer cranking to charge the oil system (Ignition off, lower plugs out, no fuel, crank 10 seconds, look for oil pressure. Still looking but that is another story I will report later...), and the two fuse blows have been at the 5-second mark. The 2 fuse blows were each on the 1st crank of the day (70 deg F ambient), 2 days in a row. After replacing the fuse, subsequent cranks (about 4 more) went fine that day.

So I was thinking that most RV-12s have never experienced current draws for multi-second start cranking, and maybe that draw is higher than thought, and maybe the new additional fan is pushing that even closer to the 2amp mark. I will report after the testing.

Bill H.
 
On the old set up.

Ive cranked my for up to 30 second s with out any problems on the old system.:)
 
A Rotax starts up quickly when you run it frequently. Not so quick when it sat f ro a while or when it's bitter cold. I cranked my older ROtax on the RANS S-12S quite a while in the winter (with the upgraded starter motor that is now standard) before it would roar to life.
Why don't you just measure what the current is that is drawn through the fuse? If the fuse holder pins are somehow accessible, put the amp meter in series and let the current run through the amp meter, then crank and see what it shows ...
 
UPDATE! This is on the 2A starter fuse blowing problem. In working with Van's, I got out the multimeter. Looks like a bad starter relay and here's why.

First, the starter circuit draws 0.22 amps to power the AV-50000A fan with the spar pins properly in. It would draw a bit more if the spar pin warning light was on. Just useful to know, because these amps are ADDED to whatever it takes to power the starter relay.

Then I did this.
I disconnected the Rotax starter power supply wire from the starter relay. This is so I could do the test without the prop spinning.
Battery is reading 12.5 V.
I put a 3 amp fuse in the starter circuit.
I wired the multimeter, set for 10 amps, in between the male spade plug on the starter relay and the female wiring that connects to it. (I made some scrap 18 gauge extension wires with cheap spade-type lugs to connect up the multimeter.)
I turn the starter switch on.
I immediately get 2.7 amps!!!
No wonder the 2A fuse is blowing.
Several tests of the starter switch give the same result.
As a test, I swap out the 3A fuse for the proper 2A fuse and repeat the test. Sure enough, it blows after about 10 seconds.

So something is up with the relay!
My relay was unmarked. Van's say they come from ROTAX. They are theorizing it is either a bad relay or a 24V relay - since it is only supposed to draw about 1.4 amps.

I measured the OHMS from the tab to the body of the relay. It is 4.6 OHMS.
Per good old V=IR, 12.5 VOLTS divided by 4.6 OHMS = 2.7 AMPS! (I don't remember the formulas to take into account DC through a coil...)
So it seems that the OHMS on the relay should read more like 9 OHMS.

So Vans is checking. If you can conveniently get at your relay, you might want to check it's resistance also.

In thinking about the above, I would think that the 24V relay theory is wrong. A 24V relay with 4.6 OHMS would draw 5.2 amps in a normal condition. That's way high. A 24V relay would seem to need MORE resistance built into the coil than a 12V relay, not less. Oh well...

More when it is concluded...
 
Final Resolution - Starter Fuse Blowing

Scott at Van's investigated the issue with starter relays they have on hand, supplied by Rotax. The relays (and there has apparently been some sort of unannounced change by Rotax) are like mine, with similar resistance, and do draw well over 2 amps.

Van's is making inquiries to Rotax. They also say "Our engineers have evaluated the circuit and it will handle 3 amps continuously so intermittent starting draws near 3 amps should not cause any problems." So if you have issues, use a 3A fuse."

They also say Auto fuses will function fine. The fuses Van's supplies with the avionics kit (3 amps and above) actually light up when they blow so if you want that type, you can order them from Van's or source them elsewhere.

+++
One other RV-12 owner guy has told me he has a 3A fuse installed since
a similar problem when new and has never blown it.

I understand the Rotax starts so fast - and the fuse seems to take
more than 5 sec to blow - that the problem is rarely encountered.

Note - 2.7 amps for the starter relay, plus .25 amps for the fan
(as tested) is still right at 3 amps.
 
Bill_H said:
Note - 2.7 amps for the starter relay, plus .25 amps for the fan
(as tested) is still right at 3 amps.
Click to expand...

Bill,
Testing just done on N412RV showed that the start circuit (with control modual fan operating) draws about 2.5 amps. in rush, and then settles at about 2.3 amps after a couple of seconds.

This would be exceptable margin for a 3 amp fuse.

I am wondering if you had a battery charger connected to your battery while you were doing your engine cranking and the amperage testing? If so, this would bump the amperage up enough to be a factor.
 
No, I always disconnect the battery maintainer before I ever turn on the master switch. Did you happen to measure the OHMS on your relay? As noted, mine was 4.6 ohms.
 
Bill_H said:
No, I always disconnect the battery maintainer before I ever turn on the master switch. Did you happen to measure the OHMS on your relay? As noted, mine was 4.6 ohms.
Click to expand...

The coil resistance of the relay in N412RV measured 4.7 ohms.
 
rvbuilder2002 said:
The coil resistance of the relay in N412RV measured 4.7 ohms.
Click to expand...
So with Ohm's Law this results in:

I = 12V / 4.7Ohms = 2.55A

or with a power supply or a fully charged battery

I = 13.8V / 4.7Ohms = 2.94A

As this is a coil in the circuit you can expect the resistance to be higher when switching on, so the current should always be below 3A, Darn close though, so make sure it's slow fuse or use a fast one at a higher rating, slightly above 3A.
 
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