201 High Low Volts Annunciator issue

[1001001]

Hi all,

I am having an issue with the HIGH/LOW VOLTS annunciator in my '78 J.  When the voltage regulator is adjusted to provide 13.8 volts on the bus (measured with a meter directly on the bus, as well as two separate instruments connected to the bus that have voltage monitors built in), the HIGH/LOW VOLTS annunciator is illuminated.  Raising the voltage to around 14.4V makes it go away but it still comes on intermittently.  14.4V is too high and will overcharge my battery.   In addition, the M20J service manual specifies 13.8V as a regulator setpoint, according to my A&P. 

My A&P says that the annunciator is driven by an output on the voltage regulator itself, and fixing this issue would require replacement of the VR.  I have not dug into the electrical diagrams yet, but can anyone verify this for me?  I have two independent methods of verifying and alerting the bus voltage independent of the factory annunciator, but really would like to get that light to turn off when things are within spec.

 

UPDATE:  I found my copy of the Service Manual and the electrical diagram specific to my serial number confirms that the annunciator is driven by an output on the voltage regulator, and that the voltage setpoint should be 13.75-14.0V with the engine at 2000 rpm.  Does anyone know if there is any option other than replacement of the VR?  It seems to be regulating just fine, but the annunciator is erroneously activating. 

Edited October 27, 2020 by 1001001

[N201MKTurbo]

http://batterymanagement.aircraft-battery.com/BatteryDocs/5-0324-rg-manual.pdf
 

If you have an RG battery, you need a higher voltage setting on your voltage regulator.

See table 1 in this document.

It will probably take care of your problem.

The airplane manual was written before RG batteries were a thing. I set my RG regulators to 14.2 V.

[PT20J]

Some regulators are adjustable. However, if it used to work correctly, something has changed. I would want to thoroughly bench check it — especially the functioning of the over-voltage protection — after any adjustments. If your A&P doesn’t have the ability to do this, I’d try an avionics shop (they are frequently more experienced at working on electrical systems).

Skip

[N231BN]

The annunciator has it's own adjustment and has nothing to do with the regulator.

M20J.pdf

Edited October 27, 2020 by N231BN

[PT20J]

Maybe I'm confused because I thought that the indication was a steady light. If the light is blinking, that's a different indication. So, to be clear:

HI/LO VOLTS blinking means low voltage. If the voltage on the bus measures correctly, then the annunciator should be adjusted.

HI/LO VOLTS on steady means overvoltage. This is driven from the voltage regulator and would be a fault or adjustment there.

Skip

[N231BN]

34 minutes ago, PT20J said:

Maybe I'm confused because I thought that the indication was a steady light. If the light is blinking, that's a different indication. So, to be clear:

HI/LO VOLTS blinking means low voltage. If the voltage on the bus measures correctly, then the annunciator should be adjusted.

HI/LO VOLTS on steady means overvoltage. This is driven from the voltage regulator and would be a fault or adjustment there.

Skip

Good points, when he said increasing the voltage to 14.4 extinguished the light I assumed it was a low voltage indication.

[Bolter]

I am not one to encourage replacing over proper diagnosing and fixing, but the voltage regulator is one of the exceptions...for me at least.  I got the idiot voltage light in my J 8 or 9 years ago and was pretty sure it was the regulator beginning to flake out since real voltage measured right.  I just put in the more modern Zeftronics unit to replace the original and did not worry about it again.  I figured I was buying future reliability on a forever plane and avoiding the costs of making lots of adjustments.  

Just my $.02 as a PP.  -dan

[1001001]

Thanks very much for the replies, guys, this is giving me some things to expand my investigation with.

 

I need to verify the solid/blinking.  I seem to think it is on solid, buthonestly can't recall right now. 

 

As for the type of battery, I will check on that.

[carusoam]

While you are checking all the boxes...

Check what voltage regulator you have....

Zeftronics, as mentioned above, Is a modern device, and has remote mounted status LEDs if desired...

If you have the old sticks and stones and springs VR... it is fun to have a car with matching numbers... but not so much when it comes to planes.... 

PP thoughts only, not a mechanic...

Best regards,

-a-

[1001001]

23 hours ago, carusoam said:

While you are checking all the boxes...

Check what voltage regulator you have....

Zeftronics, as mentioned above, Is a modern device, and has remote mounted status LEDs if desired...

If you have the old sticks and stones and springs VR... it is fun to have a car with matching numbers... but not so much when it comes to planes.... 

PP thoughts only, not a mechanic...

Best regards,

-a-

I am totally down with the idea of using a newer technology regulator if indeed the one I have needs to be replaced. 

 

I'm hoping to defer this work until the next time my panel is ripped open, hopefully sometime next spring or next fall, when I am planning to install a GFC500 and a G3X or dual G5s.

[carusoam]

10 minutes ago, 1001001 said:

I am totally down with the idea of using a newer technology regulator if indeed the one I have needs to be replaced. 

 

I'm hoping to defer this work until the next time my panel is ripped open, hopefully sometime next spring or next fall, when I am planning to install a GFC500 and a G3X or dual G5s.

My point is... if you have the sticks and stones and springs device...  it is hard to keep it operating correctly...

Yours may be more modern, and not the sticks and stones unit...  Mine boiled the battery away inflight... 

If you are going to connect expensive electronic devices to an inferior voltage regulator... that may be worth swapping out sooner than later...

Batteries cost more than the zeftronics device...
 

Some voltage regulators are mounted in convenient locations for an easy exchange...
 

The modern voltage regulators are set and forget kind of devices... they have some digital logic to drive things... 

Way more modern than the sticks and the stones...  

PP thoughts only, Not a mechanic...

Best regards,

-a-
 

 

[1001001]

48 minutes ago, carusoam said:

If you are going to connect expensive electronic devices to an inferior voltage regulator... that may be worth swapping out sooner than later...

Batteries cost more than the zeftronics device...
 

 

Oh, I definitely agree!  It totally makes sense to replace the VR with current tech when upgrading to a new digital panel.  I'm just hoping to wait until the panel is ripped out because it's a lot of effort to get back there.

Edited October 29, 2020 by 1001001

[larrynimmo]

In my 1981 m20J changing out the old Lamar VR to the zeftronics model took only minutes, and it is “Plug and play” with no wire swapping.  New one holds 14.0v pretty steady.

it is immediately accessible on co-pilot side with removing just two screw/ locknut fasteners.

[jetdriven]

1 hour ago, larrynimmo said:

In my 1981 m20J changing out the old Lamar VR to the zeftronics model took only minutes, and it is “Plug and play” with no wire swapping.  New one holds 14.0v pretty steady.

it is immediately accessible on co-pilot side with removing just two screw/ locknut fasteners.

Is it the kind with the cannon plug on it ?

[larrynimmo]

[Scott H Poms]

Zeftronics is the way to go, I have both old school and the Zeftronics and I swap them to check my alternator. ( had loads of alternator probs)  another suggestion: get an engine analyzer like a JPI unit.