Charging problem

[jerrybeach]

Under a light electrical load my M20F charges well (alternator, checked out 50 amp output, new voltage regulator, checked OK and replaced one new battery with another new battery, 12 volt system). Under a heavy electrical load the amp meter will cycle from neutral to large discharge at a regular two second cycle and it is not the strobe, l have isolated that and all other single sources as best l can. Any suggestions? Thanks, Jerry Beach 

[ShuRugal]

sounds like your regulator is seeing something it doesn't like when the alternator is under a load?  what do you have installed as far as electric power production/regulation?

[PT20J]

What’s turned on and how many amps for a “light electrical load”?

What’s turned on and how many amps for a “heavy electrical load”?

I’d start troubleshooting by pulling breakers or turning things off one at a time to see if you can isolate the load that causes the issue.

Skip

[jaylw314]

  On 9/24/2021 at 9:49 PM, jerrybeach said:

Under a light electrical load my M20F charges well (alternator, checked out 50 amp output, new voltage regulator, checked OK and replaced one new battery with another new battery, 12 volt system). Under a heavy electrical load the amp meter will cycle from neutral to large discharge at a regular two second cycle and it is not the strobe, l have isolated that and all other single sources as best l can. Any suggestions? Thanks, Jerry Beach 

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Sounds like the dirty master/alternator switch problem is a possibility, too.  Dirty contacts or poor connection there can result in oscillations in the electrical system.  If it's the external connectors, cleaning them and making sure they're secure will fix it.

Obviously not the only possibility, but it's the low-hanging fruit.

[jerrybeach]

  On 9/24/2021 at 9:49 PM, jerrybeach said:

Under a light electrical load my M20F charges well (alternator, checked out 50 amp output, new voltage regulator, checked OK and replaced one new battery with another new battery, 12 volt system). Under a heavy electrical load the amp meter will cycle from neutral to large discharge at a regular two second cycle and it is not the strobe, l have isolated that and all other single sources as best l can. Any suggestions? Thanks, Jerry Beach 

Expand  

 

  On 9/24/2021 at 10:10 PM, ShuRugal said:

sounds like your regulator is seeing something it doesn't like when the alternator is under a load?  what do you have installed as far as electric power production/regulation?

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InterAv, PN- 015-01237 alternator and Hartzell R1224S-14 regulator. Thanks for your help 

[Ragsf15e]

Also, the amp meter in these is just showing the amps going to charge the battery, not a total electrical load.

Do you have a voltage meter?  If yes, what does your bus voltage show?  If not, one can be bought inexpensively on Amazon and fit in your cig lighter.

Its pretty common on the old ones to find a corroded connection increasing resistance in the electrical system.

Edited September 25, 2021 by Ragsf15e

[jerrybeach]

  On 9/24/2021 at 10:39 PM, PT20J said:

What’s turned on and how many amps for a “light electrical load”?

What’s turned on and how many amps for a “heavy electrical load”?

I’d start troubleshooting by pulling breakers or turning things off one at a time to see if you can isolate the load that causes the issue.

Skip

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Thanks, will find out, jerry 

[RLCarter]

Hey Jerry, Your in the right place to get excellent advice….. let me finish up my annual and we’ll tag team it and see if we figure it out. Should be able to help you Wednesday (all day if needed). 

[jerrybeach]

  On 9/25/2021 at 12:56 AM, Ragsf15e said:

Also, the amp meter in these is just showing the amps going to charge the battery, not a total electrical load.

Do you have a voltage meter?  If yes, what does your bus voltage show?  If not, one can be bought inexpensively on Amazon and fit in your cig lighter.

Its pretty common on the old ones to find a corroded connection increasing resistance in the electrical system.

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Doesn't go below 12 volts, l will start looking for corroded connections and the master. Thanks to all for help, Jerry 

[jerrybeach]

  On 9/25/2021 at 12:57 AM, RLCarter said:

Hey Jerry, Your in the right place to get excellent advice….. let me finish up my annual and we’ll tag team it and see if we figure it out. Should be able to help you Wednesday (all day if needed). 

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Thanks, Jerry

[jerrybeach]

  On 9/25/2021 at 12:41 AM, jaylw314 said:

Sounds like the dirty master/alternator switch problem is a possibility, too.  Dirty contacts or poor connection there can result in oscillations in the electrical system.  If it's the external connectors, cleaning them and making sure they're secure will fix it.

Obviously not the only possibility, but it's the low-hanging fruit.

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Thanks, Jerry 

[Ragsf15e]

  On 9/25/2021 at 1:04 AM, jerrybeach said:

Doesn't go below 12 volts, l will start looking for corroded connections and the master. Thanks to all for help, Jerry 

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Well bus voltage should be at 14v.  Literally 14+/-0.2v or so.  If your engine is running and the vr and alternator are working, bus voltage should stay right at 14v with any reasonable load.  Usually we’ll see corroded connections show as say 13v or so.  Still higher than battery voltage, but not 14v as the alternator should be putting out.  If you’re down at 12.4ish, that’s pretty much battery voltage, so is the alternator providing anything?

[A64Pilot]

  On 9/25/2021 at 12:41 AM, jaylw314 said:

Sounds like the dirty master/alternator switch problem is a possibility, too.  Dirty contacts or poor connection there can result in oscillations in the electrical system.  If it's the external connectors, cleaning them and making sure they're secure will fix it.

Obviously not the only possibility, but it's the low-hanging fruit.

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I’d start here too. It’s occasionally the switch itself, it’s very easy to jumper the switch to verify it as they aren’t cheap and don’t seem to be easy to get.

I put a dab of DC-4 silicone grease (same stuff you use on the oil filter o-ring)  to prevent further corrosion. The corrosion to prevent good contact is so slight t you can’t see any so even if the terminals look good, clean them anyway

[jerrybeach]

  On 9/25/2021 at 1:42 AM, Ragsf15e said:

Well bus voltage should be at 14v.  Literally 14+/-0.2v or so.  If your engine is running and the vr and alternator are working, bus voltage should stay right at 14v with any reasonable load.  Usually we’ll see corroded connections show as say 13v or so.  Still higher than battery voltage, but not 14v as the alternator should be putting out.  If you’re down at 12.4ish, that’s pretty much battery voltage, so is the alternator providing anything?

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Thanks for your advice 

[Yetti]

The master solenoid is in the back of the plane so probably not.   I would redo the big lug at the alternator and check the all the connections at the master bus and CB panel.  Rebuild the alternator harness while you are there.  Even the connections at the amp meter shunt should be suspect.    build up of current limiting corrosion on lugs and wires is pretty common.

Edited October 2, 2021 by Yetti

[Guest]

Have you checked drive belt tension?  You need to know if it’s an indication issue or an output issue.  Connect a good volt meter to the main buss and see if voltage fluctuates coincident with the ammeter.  If both fluctuate I’d full field the alternator and see what happens.  Disconnect the field wire, secure it out of the way, make and run a jumper wire from the jumper alternator output terminal to the field terminal, you have removed the regulator from the circuit.  Turn on the master switch, the alternator core should now be magnetized, start the engine, observing both the voltmeter and ammeter, remember that RPM now controls output in an upward spiral. If both are steady you’ve proven that the alternator is good and the trouble lies in the regulator control circuit.

Clarence