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  #31  
Old 06-24-2017, 07:24 PM
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tomkk tomkk is online now
 
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Location: Port Orange, Fl
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Quote:
Originally Posted by Mich48041 View Post
Did you buy the master switch from Van's?
Good question. I got it from Mouser. Not sure why I didn't get it from Van's. I would have thought that I would have tried them first - don't remember why, it was a while ago.

Quote:
To check the master switch, disconnect the D-Sub connector from the AV-50000A that goes to the IGNITION MODULE. Then turn the master switch on and measure continuity between pins 13 and 14.
If the master switch is bad and you do not want to wait until a new one is delivered, regulator terminal "C" can be jumpered to terminal "B". The disadvantage of doing that is that in case of smoke in the cockpit while flying, the master switch will not shut down the electrical system. It would be necessary to pull the alternator fuse.
I saw that in the picture in the "Testing a VR" you posted earlier. Wasn't sure what that was for. Good to know ...
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RV-12 N121TK ELSA #120845
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  #32  
Old 06-25-2017, 01:05 AM
E. D. Eliot E. D. Eliot is offline
 
Join Date: Dec 2005
Location: San Pedro
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Default Suggestion

When my kids were in college, I maintained a fleet of four well used but pretty reliable small 1996 Oldsmobiles for them. I grew pretty good at finding and solving electrical problems with that fleet of four. Initially when there was an electrical problem, I searched for open grounds or broken wires, bad fuses, etc. This was effective and solved most of the problems.

On one car with an apparently unsolvable problem (b.o. radio), I pretty much gave up - but then I removed all of the fuses and replaced them. Problem solved.

So, I have learned to be suspicious of fuses. I recommend that you replace the appropriate fuses even if they check ok. Do the cheap and simple things first. Sounds to me like a blown fuse or two or bad ground has haunted you for quite a while.
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  #33  
Old 06-25-2017, 08:29 AM
Mich48041 Mich48041 is offline
 
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Digital voltmeters can be misinterpreted. Supposing that a digital meter is used to measure the voltage at the downstream side of a blown fuse and the meter reads 1.75 volts. Is it really 1.75 volts? If a load is connected that requires 1.75 volts, would it work? No, it would not. So is the meter lying? No, it is displaying exactly what it sees. If a digital meter has, say, 5 megohms of resistance and it is connected in series with a blown fuse with a resistance of 30 megohms, an infinitesimal amount of current flows from the source through the blown fuse and through the meter back to the source. If the source is a 12.75 volt battery, then 11 volts are dropped across the blown fuse and 1.75 volts are dropped across the digital meter. The meter reads 1.75 volts.
If a 5 watt, 12 volt, indicator lamp is connected as a load, now the meter will read zero because the infinitesimal current is flowing through the lamp instead of the meter. I like to test a circuit when it is under load to get more meaningful meter readings. By the way, the definition of infinitesimal is the distance that an aircraft carrier sinks in the water when a fly lands on its deck. :-)
Fluke Meter pdf talks about input impedance.
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  #34  
Old 06-26-2017, 03:36 PM
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tomkk tomkk is online now
 
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Default Not much progress today ...

I still haven't been able to isolate my problem. Here's what I did/saw today:
  • The battery seems to be holding a charge OK (12.75v).
  • Checked and verified good continuity all the way from the small yellow wire at the VR (VREG CNTRL) to the Switch & Fuse Module (AV-50001) via:
    • Control Module (AV-50000A) WH-00063 (21) & WH-00030 (14)
    • Ignition & Start Module (AV-50002) WH-00030 (14) & WH-00030 (13)
    • Control Module (AV-50000A) WH-00030 (14) & WH-00031 (23)
    • Switch & Fuse Module (AV-50001) WH-00031 (16)
  • Checked and verified that the Master Switch correctly made & broke continuity of the VREG signal between pins 13 & 14 of WH-00030.
  • Confirmed battery voltage (12.75v) on the Battery input of the Switch & Fuse Module.
  • ?? With 12.75v on the battery input of the Switch & Fuse Module and with the D-Shell disconnected, measured 9.7v on the VREG WH-00031 (16) S & F module output.
  • Just to verify another S & F module output, I checked the Fuel Pump output (WH-00031 pin 1) and it was at 12.75v.
  • Also measured 9.7v on pin 23 of the Control module end of WH-00031.
  • ?? I couldn't figure out how to measure intermediate voltages between the Control module VREG input, WH-00031 (23), but the voltage at the small yellow VR wire continued at the 1.75v I previously saw.
  • Visually checked the 1A VREG fuse on the S & F module. There was no visual difference between that fuse and the other two fuses on the circuit board but I have no idea if there's any visual indication if these fuses blow.

So, I'm still at a loss. Tomorrow I guess I'll go out and see if I can see some way to check intermediat voltages between the Control module that's at 9.7v to try to see where it drops to the 1.75v I see at the small yellow wire.

I don't understand the drop to 9.75v S & F module VREG output.
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RV-12 N121TK ELSA #120845
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  #35  
Old 06-26-2017, 09:42 PM
Mich48041 Mich48041 is offline
 
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Instead of using a voltmeter, use a 12 volt test light. The test light should NOT have an internal battery. It should have a light bulb that lights up when connected to the aircraft battery. The wattage of the test light should be 3 watts or less. Any larger than that risks blowing the 1 amp fuse, if it is not already blown, which is a good possibility.
Does the tester illuminate when connected to the voltage regulator output from the switch and fuse module?
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  #36  
Old 06-27-2017, 08:55 AM
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Tommycat Tommycat is offline
 
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Location: North-western Illinois
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Default Bad fuse(s)...?

Quote:
Originally Posted by tomkk View Post
Tomorrow I guess I'll go out and see if I can see some way to check intermediat voltages between the Control module that's at 9.7v to try to see where it drops to the 1.75v I see at the small yellow wire.

I don't understand the drop to 9.75v S & F module VREG output.
Cat troubleshooting rule #1...always start with the obvious. 9.75v is not right.

Follow electrical safety precautions.

Keeping your meter negative lead (common port) at the same grounding location. Probe to good metal contact with your meter positive lead (V positive port), meter selection on DCvolts.

Unit powered up, and connector disconnected...

Probe all three soldered on fuses, first at their power in lead. Then at their power out lead.

All 6 test points should read Battery voltage. (your 12.75v)

If it drops at all across the fuse, the fuse is bad. If the power in is low, the problem is further upstream. If they all check good, your problem is downstream.

Remember, a bad fuse is a result of a problem. Typically not the problem itself.


Regards,
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  #37  
Old 06-27-2017, 10:42 AM
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tomkk tomkk is online now
 
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Quote:
Originally Posted by Mich48041 View Post
Does the tester illuminate when connected to the voltage regulator output from the switch and fuse module?
Ok, the tester does not illuminate on the vreg output on the back of the s & f module. It does illuminate on other outputs (fuel pump) so the tester is working. If I understand the schematics correctly, that pretty clearly points to the 1a fuse?
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  #38  
Old 06-27-2017, 11:19 AM
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Tommycat Tommycat is offline
 
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Jumper the fuse and re-test pin 16. Check pin 23 while your at it... Caution this assumes the short(s)to be elsewhere. (Out of S&W module.) Quick amp draw check?

Recommend testing points in my previous post.
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Last edited by Tommycat : 06-27-2017 at 11:34 AM. Reason: Caution
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  #39  
Old 06-27-2017, 11:58 AM
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I don't think I have a good way to test those points without a bench setup for the module. The fuses are mounted on circuit board where the module has to be disssembled to get at them.
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  #40  
Old 06-27-2017, 10:51 PM
jpowell13 jpowell13 is offline
 
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Default Battery Lead?

You may have checked this, but my battery began to discharge on my 6A in flight; then, the alternator would charge fine when I was on the ground. Turned out to be a loose crimp on the battery lead at the alternator. John
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