Alternator issues

[Pictreed]

I noticed last weekend that when I turn on my old incandescent head light the voltage drops to about 12.3V. Is this an alternator issue or maybe I've never noticed the drop?

I downloaded the Plane Power trouble shooting article suggested in another thread that I'll go through in the mean time.

It's time to get a new belt so I figured since the prop and belt are off if it needs an IRAN or replacement that I should do it now.

I prefer it not quit in heavy IMC. BTW, a 65 E leaks a lot of water heavy downpour in the clouds. I need to figure that out or stop flying in the rain.

Tim

[N201MKTurbo]

An LED landing light is a lot cheaper than an alternator.

The old landing lights draw a lot of current. To tell if it is the alternator, you need to connect a voltmeter to the alternator output. The landing light could be pulling down your bus downstream of the alternator.

[rklems]

What is your bus voltage normally (without the landing light)? What is the rated output of your alternator and what kind of load are you running typically? I don't recommend randomly shotgunning parts, and wouldn't start OH'ing or replacing parts before someone fully troubleshoots the system and determines where the problem lies. 

[Hank]

My Owners Manual says to turn on the landing light and watch the ammeter needle wiggle as part of the Post-Engine Start checklist. Proves that the meter still works.

Best thing to do is test it while the prop is off. Check your field wire, too--mine just broke, thankfully in VFR conditions. 

[Pictreed]

I have a JPI 700 for the voltage. Typical voltage is around 13.8 with the IFD440, Garmin Nav/com 2, sky track in/out nav lights and strobes were all on before I turned on the landing light. 

[N201MKTurbo]

32 minutes ago, Pictreed said:

I have a JPI 700 for the voltage. Typical voltage is around 13.8 with the IFD440, Garmin Nav/com 2, sky track in/out nav lights and strobes were all on before I turned on the landing light. 

It matters where the JPI is measuring the voltage. I assume it is using its power wire. The measured voltage may be different than the alternator output depending on the voltage drop between the alternator and the JPI. The voltage drop depends on the buss resistance and the current flow through the bus between the alternator and the JPI.

[Echo]

You can get a much better and longer lasting LED landing light used on ebay for a hundred bucks.  You will likely never need another landing light.  The draw is minimal compared to old tech lights.  It is a no brainer upgrade.

[MikeOH]

35 minutes ago, Echo said:

You can get a much better and longer lasting LED landing light used on ebay for a hundred bucks.  You will likely never need another landing light.  The draw is minimal compared to old tech lights.  It is a no brainer upgrade.

I went for the AeroLites which was $145 at the time (7 years ago) and had my A&P do a 337 since they are technically not FAA/PMA approved.

[Bartman]

At last annual I/we installed a new WAT Parmethus PAR 46 landing light along with LED wing tip lights and I am very happy with the result. However, I must say that in the 18 years that I have owned 1TF the GE landing light has only been replaced once, and that was about 15 years ago. That being said, the WAT was expensive, but the LED is so much brighter and I’m happy with my purchase. 

[DXB]

+ 

3 hours ago, Pictreed said:

I noticed last weekend that when I turn on my old incandescent head light the voltage drops to about 12.3V. Is this an alternator issue or maybe I've never noticed the drop?

I downloaded the Plane Power trouble shooting article suggested in another thread that I'll go through in the mean time.

It's time to get a new belt so I figured since the prop and belt are off if it needs an IRAN or replacement that I should do it now.

I prefer it not quit in heavy IMC. BTW, a 65 E leaks a lot of water heavy downpour in the clouds. I need to figure that out or stop flying in the rain.

Tim

Agree an LED is the way to go, but what you have is not normal and should be sorted regardless. Does turning on your pitot heat do the same? It should be a comparably large electical load I think? Yes or no might help trouble shoot where the issue is.  I'll leave it to the folks with more expertise on how electrons move about to figure this one out

[Bartman]

2 hours ago, Hank said:

My Owners Manual says to turn on the landing light and watch the ammeter needle wiggle as part of the Post-Engine Start checklist. Proves that the meter still works.

Best thing to do is test it while the prop is off. Check your field wire, too--mine just broke, thankfully in VFR conditions. 

In 18 years of ownership we have repaired the field wire terminal 3 times.  The vibration causes the wires to break at the crimp.  In 2020 when we installed the rebuilt engine I coiled up a small loop of extra field wire at the alternator and secured it such that there was minimal movement between the wire loop and the terminal. I installed a new terminal and decided I would just install a new terminal in years divisible by 5.

It looked good this year but I replaced it anyway. Good for another 5 years.

I think the field wire terminal is the weakest link on the M20J 

[Andy95W]

Are you sure you have an alternator?  The 65 M20E was originally equipped with a generator.  Your symptoms would be normal for a generator below 1500 rpm with the landing light on.

[Pictreed]

Lots of good ideas where to start. Thanks. I’ll report back. 

[Pictreed]

30 minutes ago, Andy95W said:

Are you sure you have an alternator?  The 65 M20E was originally equipped with a generator.  Your symptoms would be normal for a generator below 1500 rpm with the landing light on.

Yeah, pretty sure. 

[Pictreed]

5 hours ago, rklems said:

What is your bus voltage normally (without the landing light)? What is the rated output of your alternator and what kind of load are you running typically? I don't recommend randomly shotgunning parts, and wouldn't start OH'ing or replacing parts before someone fully troubleshoots the system and determines where the problem lies. 

You’re right, I never throw parts at it. That’s the biggest reason I do my owner assist. Too many times a well meaning mechanic replaced a good part.