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No Joy with Diagnosis of Negative Amps & Declining Volts

Tony,

Thanks for this. Two questions:

1. Is D-Sub pin 13 now an open unused pin, or would the new fuse wire share that pin with another wire that's already attached?

2. In your photo, it looks as though the Ignition Harness is routed through a black tube, just below the red shrink wrap, and that the black tube is much narrower than the D-Sub. If so, how would I get the Harness out of the plane and then back in again. Or is the "tube" actually part of the D-Sub itself, so that once I get access to it, I'll be able to take it out without passing it through anything?

1. Pin 13 is a used pin. It is the connection that carries the voltage from the 1 amp fuse (that burned out) to the Master Switch. When the master is ON that voltage then goes out through Pin 14 to the VR sense wire. Pin 13 has a white/yellow wire. The new fuse wire could be spliced to that wire and the D-Sub's at either end of the harness would not need to be disassembled.
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If I were doing this I would disconnect the battery first. Use a ohmmeter to check continuity from the new fuse wire to pin 13 and also pin 13 to pin 13 on each end of the harness. The pin numbers can be read on the end of the connector but they are really small. Be careful reinstalling D-Subs so as to not bend any pins.

2. There is no black tube, just a D-Sub connector at each end of the short WH-00030 harness. The red shrink wrap just goes into the D-Sub.

P.S. If you are new to this it would be good to review Section 5-21 (Electrical) of the KAI which is downloadable from Van's website.
 
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My soldered-in fuse experience

On one of our student-built planes, the notorious fuse discussed above blew during flight, such that the amps display went negative. We diagnosed the root cause and did the work around of tying the C input to the battery, sacrificing the master switch light function in the process. Several months later, the main battery voltage and amperage displayed on the Garmin G3x went non-functional. This was traced to yet another blown soldered in fuse in the AMPS A or AMPS B signal on the same AV-5001 module. This motivated us to replace all three soldered-in fuses on the board with small ATM fuses placed on the edge of the card for easier replacement if any were to blow again. We did not un-do the workaround--kept the C input jumpered to the battery--this jumpering is the preferred wiring in the Rotax engine manuals, and we didn't want the voltage regulator going non-functional if the fuse ever blew again.
 
On one of our student-built planes, the notorious fuse discussed above blew during flight, such that the amps display went negative. We diagnosed the root cause and did the work around of tying the C input to the battery, sacrificing the master switch light function in the process. Several months later, the main battery voltage and amperage displayed on the Garmin G3x went non-functional. This was traced to yet another blown soldered in fuse in the AMPS A or AMPS B signal on the same AV-5001 module. This motivated us to replace all three soldered-in fuses on the board with small ATM fuses placed on the edge of the card for easier replacement if any were to blow again. We did not un-do the workaround--kept the C input jumpered to the battery--this jumpering is the preferred wiring in the Rotax engine manuals, and we didn't want the voltage regulator going non-functional if the fuse ever blew again.

Did you, by any chance, take photos of the board after you installed ATM fuses on its edge? If you did, I'd love to see them.
 
This is specifically addressed to Scott. Do you have the specifications, make, model, etc. for those 1 amp fuses that are mounted on the switch module circuit board. I would like to replace one and it will be easier if I know I am ordering the correct fuse. The circuit boards have Van's numbers for those parts, ES-00190. I don't know where there is a table to convert VAn's numbers to a part number for a supplier. If I can get a part number, it will be easy to buy some fuses and replase the one bad one.

Thanks.

John D.Young
 
I want to replace the 1 amp fuse that powers the VR. To do so, I need to know the correct part number, not Van's part, but the manufacturer part or type. I am attaching a picture of the circuit board. The brown item on the far right is the fuse for the VR. The other two brown items are the fuses for Amps A and Amps B.

Can anyone help me fine the correct fuse part number and type?
opT.jpg
 
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This is specifically addressed to Scott. Do you have the specifications, make, model, etc. for those 1 amp fuses that are mounted on the switch module circuit board. I would like to replace one and it will be easier if I know I am ordering the correct fuse. The circuit boards have Van's numbers for those parts, ES-00190. I don't know where there is a table to convert VAn's numbers to a part number for a supplier. If I can get a part number, it will be easy to buy some fuses and replase the one bad one.

Thanks.

John D.Young

Sorry John
I never saw this post or I would have replied.
The correct Van's part # for the fuse is ES-191.

The ES-190 is a fuse socket/holder that late in the design process was deleted because it did not hold the fuse tightly and there was concern about vibration influence over time. Soldering them in made it much more secure but it does make it a little more of a pain to replace.
If anyone ever wants to purchase a fuse from Van's and replace it your self, you should be able to do that using the ES-191 #.

The manufacturer info for the one used is -

Little Fuse / Fuse 1A / Manuf. Part # 38511000440

The one that Brian linked you to is slightly different. It has traditional long leads that that can be bent over which will make it easier to keep in place while it is soldered. The original part has heavier leads that were intended to insert into the socket that is not being used.
The long lead version will work fine as long as you make sure you get the 1 amp value but I recommend that especially with the long (soft) lead version, you re-apply hot melt glue to stabilize it from vibration.
 
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Scott,

Thanks. I didn't think Van's would sell these fuses. I got that number off the drawing thinking it was the fuse number. I appreciate your giving me the details.

Also I saw something on the circuit board around the fuses that I couldn't identify. I guess it is the hot glue. I already order some fuses so I will just use one of those.

This is a total curiosity question. The circuit board and the wiring diagram also have an optional LED and 1K resister not far from where the fuses are. They are not installed. Do you know what that was going to be?

Thanks for your help.

John
 
The circuit board and the wiring diagram also have an optional LED and 1K resister not far from where the fuses are. They are not installed. Do you know what that was going to be?

Thanks for your help.

John

It was an attempt to plan ahead for potential future enhancement.

There was originally consideration to having a face plate that would have back lighted placarding text for each of the switch functions. Because the cost of producing it on the pcb was basically zero, it was added to the initial design because making a change does have a measurable cost.

I think there is a very low chance that would ever be implemented now at this point, but because of the cost point I mentioned above, there is really no good reason to delete it.
 
Also I saw something on the circuit board around the fuses that I couldn't identify. I guess it is the hot glue.

Very often circuit boards will be dipped in a clear conformal coating that is cured with UV light to seal the components from moisture. Perhaps that is what you're seeing.
 
Very often circuit boards will be dipped in a clear conformal coating that is cured with UV light to seal the components from moisture. Perhaps that is what you're seeing.

No, as mentioned, it is probably the hot melt glue that is applied to the fuses to stabilize them against vibration.
 
No Joy

Scott,

I replaced the 1 amp fuse and now the LED on the Master Switch lights up. A very minor point but it was bugging me to not have it lighted up. I left the wiring with the revised plan for the SH voltage regulator, jumping the two terminals on the VR. I do recognize that shutting off the Master Switch will not shut off the VR. I will have to pull the 30 amp fuse to shut off the VR.

I have another question. Is it possible to buy the trim switch from Van's? If so what is the part number?

Mine is broken on the edge and glued. It works fine but I would like to replace it.

Thanks.

John
 
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