MEP-803a panel lights flickering

m32825

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I appreciate the coaching, you guys are great!

CR1 looks okay visually, I tugged on it some with no change in behavior. This is an intermittent issue though, took me half an hour to catch the clip above, so that complicates the verification process.

I have a 24V test lamp with alligator clips. Is there something I could clip it across that would give us useful data next time the panel flickers? Like, if the panel flickers but the test light doesn't, we know it's something beyond that point?

I put a new alternator in last year hoping it might fix the flicker. Since the flicker behavior didn't change I'm thinking the cause lies elsewhere.

DigiKey is sending me diodes, will replace CR1 when they arrive. Will check MT4 next, and I appreciate that warning Guy, because in post #12 of this thread I already did some arc welding! 🙂

-- Carl
 

Scoobyshep

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Here is a thought get a meter that has a min max function. Use the wiring diagram to find a point about halfway in the circuit. Set the meter to min mode and if it still dips down its closer to the source. If it does not catch the flicker its closer to the load.

Sent from my SM-G973U using Tapatalk
 

m32825

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I haven't had time to do much with my system but it has been sitting on the driveway so when I have a few minutes in the evening I go mess with it to see if I can identify a pattern to the flickering. I found that the flickering seems to connected to a change in the sound of the fuel pump. In this video I don't even start it, just put the switch in the run position.

 
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Light in the Dark

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I didn't see the video, but it would make sense that if there is an issue on the 24V side you would hear a change in the 24V powered pump.
 

m32825

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Interesting that it happens without running, that eliminates the whole charging side doesn't it? Not sure if the pump is the cause or just another effect. Not sure what the deal is with the video, will investigate.
 

nextalcupfan

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To me it looks like a bad connection somewhere, during your last video I noticed the fuel gauge was also moving somewhat erratically.
This tells me you have a bad connection on either a main ground or main power.

If it were me I would take EVERY connection starting at the battery terminals apart (as realistically as possible) and clean them with something abrasive. (I like green scotchbrite)
If you have any on hand I would also spray the 3 plugs that comes into the main panel with Deoxit cleaner. (J5, J6 and J6 I believe)


Guyfang mentioned earlier about someone with a working 803a taking measurements on ohms to ground, I would be more than happy to do this if you just tell me exactly which measurements to get. I have a Fluke 17B DMM with Kline leads so I'm fairly confident in the measurement accuracy.
 

m32825

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Guyfang mentioned earlier about someone with a working 803a taking measurements on ohms to ground, I would be more than happy to do this if you just tell me exactly which measurements to get. I have a Fluke 17B DMM with Kline leads so I'm fairly confident in the measurement accuracy.
Thanks for that. I'm getting 1.4 ohms between any pair of ground screws on the back of the oil pressure, temperature, and fuel level gauges.
 

Ray70

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Out of curiosity have you tried unplugging the main fuel pump, to see if the pump itself is causing a voltage issue?
I think you may want to try to find the source of the problem by progressively removing items from the circuit until the issue stops.
 

m32825

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Out of curiosity have you tried unplugging the main fuel pump, to see if the pump itself is causing a voltage issue?
I think you may want to try to find the source of the problem by progressively removing items from the circuit until the issue stops.
Good suggestion, will try.
 

m32825

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Okay, tried unplugging the pump. No variation in the lights with the pump unplugged and the switch in the prime and run position, engine not running.

I repeated the test with the aux pump running, but not the engine, and it behaves the same way as when the main pump is in the circuit. That is to say, flickering.

I said I was going to check the MT-4 shunt but cannot find it. I see it on the exploded parts diagram but am having a failure of imagination. Help me narrow it down?
 

kloppk

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Instead of messing with messing with MT4 I'd suggest installing a jumper wire between the two top terminals of MT4. Be sure to disconnect the batteries first. The jumper will bypass MT4.
See if the flickering stops.
If it doesn't then it's not MT4.
 

kloppk

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Do you have any LED's and resistors laying around?
I have an idea on how to make a tester to track down the problem. :cool:
If you don't I can make one and mail it to you.
 
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kloppk

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As you know LED's require little voltage to light up. A flicker tester could be made by adding a current limiting resistor to an LED. Then add two wires to it to use as probes.
If it's then attached across two points in a circuit and there is momentary voltage drop the LED will blink.
Would need to be connected to the circuit with the correct polarity.

For example if you connect it across MT4 and MT4 is the problem the LED will blink each time there is a panel light flicker.
 
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