Alternator Upgrade

How to keep the Cessna 170 flying and airworthy.

Moderators: GAHorn, Karl Towle, Bruce Fenstermacher

reecewallace
Posts: 163
Joined: Tue Jan 05, 2021 1:34 am

Alternator Upgrade

Post by reecewallace »

I want to upgrade my 56' 170b from the old lower-power 20amp Delco Remy generator to a new alternator to provide more power.

I'm looking for advice on which alternator to order from ACS and what other parts/accessories will be required.

Obviously, I need an alternator, but what else?
- Voltage regulator?
- Circuit breaker panel? (my plane only has fuses)

I have an O300-A.

Kindly talk to me as if I'm a child as my knowledge of electrical systems is slim to none.
- Reece
1956 Cessna 170b
Nanaimo, BC Canada
User avatar
Bruce Fenstermacher
Posts: 10303
Joined: Tue Apr 23, 2002 11:24 am

Re: Alternator Upgrade

Post by Bruce Fenstermacher »

Reece, the most important thing you can buy with your alternator upgrade is the approval to make this change in the form which would likely be a STC. You just can't buy a Ford alternator and regulator and install it for example.

The approval will specify the voltage regulator you need as well as any other equipment. It will specify the minimum wire sizes needed. You will need 2 fuse holders or circuit breakers and one of these could be your current fuse holder or if you choose 2 circuit breakers. The size of the circuit protection might be specified by the install instructions and if not if they would have to be sized to protect the wire in each circuit.
CAUTION - My forum posts may be worth what you paid for them!

Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
User avatar
cessna170bdriver
Posts: 4058
Joined: Mon Apr 22, 2002 5:13 pm

Re: Alternator Upgrade

Post by cessna170bdriver »

I’ve had a 50-amp Jasco alternator with Skytronics regulator since 1990 and have had absolutely no issues with it. I had it overhauled along with the engine in 2006 at about 1000 hours and have put over 800 hours on it since then. ACS says this one comes with the alternator, regulator, and STC.

You’ll also need a 50-amp circuit breaker for the alternator output, circuit breakers for the regulator and field (check instructions for sizes), 6-awg wire and terminals, and assorted other wire and terminals. I’m not sure whether the STC allows for substitution of fuses. I replaced the original fuse panel with all circuit breakers.

Your current drive gear will work but you’ll want a new drive cup and rubber bushings (these should be replaced about every 500 hours).
Miles

“I envy no man that knows more than myself, but pity them that know less.”
— Thomas Browne
User avatar
GAHorn
Posts: 20921
Joined: Fri Apr 12, 2002 8:45 pm

Re: Alternator Upgrade

Post by GAHorn »

Actually you can buy a Ford alternator, regulator and install it …if you do so in accordance with the Cessna Service Kit instructions….and submit a 337 for approval in Block 3….(this SK was originally applicable to O300-powered 172s)…..found in the MX Library: viewtopic.php?f=36&t=6663
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
User avatar
Bruce Fenstermacher
Posts: 10303
Joined: Tue Apr 23, 2002 11:24 am

Re: Alternator Upgrade

Post by Bruce Fenstermacher »

GAHorn wrote:Actually you can buy a Ford alternator, regulator and install it …if you do so in accordance with the Cessna Service Kit instructions….and submit a 337 for approval in Block 3….(this SK was originally applicable to O300-powered 172s)…..found in the MX Library: viewtopic.php?f=36&t=6663
I should have said Chrysler not Ford. :roll:

The point I was making is you must have a bases of approval for any alteration. Following a Service Kit instructions as George points out is one of them.
CAUTION - My forum posts may be worth what you paid for them!

Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
reecewallace
Posts: 163
Joined: Tue Jan 05, 2021 1:34 am

Re: Alternator Upgrade

Post by reecewallace »

Bruce Fenstermacher wrote:Reece, the most important thing you can buy with your alternator upgrade is the approval to make this change in the form which would likely be a STC. You just can't buy a Ford alternator and regulator and install it for example.

The approval will specify the voltage regulator you need as well as any other equipment. It will specify the minimum wire sizes needed. You will need 2 fuse holders or circuit breakers and one of these could be your current fuse holder or if you choose 2 circuit breakers. The size of the circuit protection might be specified by the install instructions and if not if they would have to be sized to protect the wire in each circuit.
Appreciate this.

I have no intent on installing an automotive alternator in my plane. I'm looking for a certified & STC'd alternator, and am looking for recommendations.

Additionally, we have no field approval or form 337 available in Canada. Everything must be certified, STC'd and approved.

Any suggestions on brands to go with? Preferably something as a package deal which includes alternator, wires, circuit breaker etc. I'd like to order something from ACS soon, but don't want to be missing parts & components once it's all torn apart.
- Reece
1956 Cessna 170b
Nanaimo, BC Canada
User avatar
Bruce Fenstermacher
Posts: 10303
Joined: Tue Apr 23, 2002 11:24 am

Re: Alternator Upgrade

Post by Bruce Fenstermacher »

Reese,

The Ford alternator George and I mentioned is an aircraft alternator made by Ford and is installed on many 170s back in the day. I don't know but wouldn't be surprised to find the Jasco alternator is a Ford or a Ford knock off alternator.

I can't recommend a STC'd alternator kit, perhaps someone else can. But I can say with some confidence no STC's kit will come with wire and the circuit breaker as the supplier could never offer the exact right components for every installation. They will have guidance in the STC instructions what type or size components you might need. If you are set on going the STC route I'd ask the vendor for a copy of the installation instructions and needed hardware before you buy the kit so you can include the best guess of the things you will need.

And last, are you aware you can swap out your 20 amp generator for a 35 amp generator and regulator. This is approved by Cessna and only a log entry and it is practically a bolt in swap. You would have to insure the wire from the generator is rated to carry 35 amps and swap it out if not and you will have to remove your 20 amp fuse and install a 35 amp fuse in your current holder. As for the generator wire yours is likely already large enough as Cessna installed appropriate size wire for the optional 35 amp generator but again you would have to check to be absolutely sure. With the advent of LED lighting 35 amps is a lot more than it use to be. Your incandescent nav lights can account for 15 amps alone.
CAUTION - My forum posts may be worth what you paid for them!

Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
User avatar
GAHorn
Posts: 20921
Joined: Fri Apr 12, 2002 8:45 pm

Re: Alternator Upgrade

Post by GAHorn »

Reece, in addition to what Bruce posted, you’d also need replace the 20A regulator with a 35A regulator. Frankly, if it were my choice to make…that’s exactly what I’d do…. trade-in the 20A gen as a core for a replacement 35A generator…and install a Zeftronics regulator to control the new 35A gen.
Not only would it be a simpler modification, it already has an approval basis without great expense.

With modern avionics and L.E.D. lighting…35 Amps is more than sufficient and a generator system is more robust (less likely to be damaged by operations) than any alternator system. It would also still “excite” and recharge a dead battery without additional or extra-ordinary efforts.

I have two airplanes with this engine…one with a 35A gen system….and one with the 50A Jasco STC’d system. If either system should need overhausl….the Jasco would have to go back to the factory… and would cost as much as a new system….while the generator could be overhauled by any number of shops for about $200 or less.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
User avatar
ghostflyer
Posts: 1387
Joined: Mon Apr 21, 2008 3:06 am

Re: Alternator Upgrade

Post by ghostflyer »

I would be doing a load analysis of the electrical system and including dead battery situation. In Australia we have to have a listing of all electrical loads in our log book. I had a STC for a 100amp alternator when I put the Lycoming in originally. While it worked a treat it was a massive overkill. [It was given to me ] . Now there is a 45 amp alternator due to all Led lights ,light weight starter and new instruments and radios. But realistically a 25 amp alternator would be workable for me . EG, After start there is a draw of about 6 amps for about 3 minutes and then for about 4 minutes 3 amps and then about 1.8 amps for the rest of the flight. Voltage is around 14.2 volts . [This is day time flying ].
User avatar
dstates
Posts: 471
Joined: Sun Jun 30, 2019 5:50 pm

Re: Alternator Upgrade

Post by dstates »

And here I am over here running a 12A generator ;)

I did make my situation better by replacing all lights with LED lights. That allowed me to put in other avionics like a GTX 375 and dual G5's. I was able to show on paper during the installation that everything I put in consumed less current than what was in there before. I also did a load analysis and am good there too. I'd love to have some more margin so I will probably upgrade at some point in the future.
N1235D - 1951 170A - SN: 20118
User avatar
Vertical
Posts: 151
Joined: Mon Oct 08, 2018 12:41 am

Re: Alternator Upgrade

Post by Vertical »

I have personal experience installing a couple different alternator upgrades in a couple different 170's.

Best two options I'm aware of for easy modern conversions:

1. Plane Power (Hartzell) ER14-50. The kit from aircraft Spruce come with wire harness, gaskets, placard, regulator and panel warning light. You just hook up to exiting breaker (or change/upgrade as necessary depending on current config. -Actually, you might need to pick up a new gasket for the 0-300A (The symmetrical tach/alt combo type- and make sure you replace the entire thing, and don't cut the tach drive part off).
The conversion is STC'd. Install is easy and it's well regarded by an electrical guru I respect. Total weight is 6.9# for alternator and .34# for Regulator.
They also have a gear assembly that's less expensive than Continental if yours needs replacement: Part number: ER14-GR

https://www.aircraftspruce.com/catalog/ ... key=391876

2. BC433-H 30. This is 4.4#, gear drive, 30amp alternator. Very light and proven equip. It's not certified, however private and commercial operators put them on Continental and Lycoming engines with various approvals often. For the 170, there is a an STC and kit that includes every single last connector, washer, nut, wire, circuit breaker, switch, gasket.....etc that you possibly need for the install. Includes new drive gear (you send back yours as core).

Link to the alternator, not the STC Kit:
https://www.aircraftspruce.com/pages/el ... rDrive.php
User avatar
Vertical
Posts: 151
Joined: Mon Oct 08, 2018 12:41 am

Re: Alternator Upgrade

Post by Vertical »

Reece,
Sent you A PM.
User avatar
dstates
Posts: 471
Joined: Sun Jun 30, 2019 5:50 pm

Re: Alternator Upgrade

Post by dstates »

more info on the B&C option

viewtopic.php?f=24&t=14131
N1235D - 1951 170A - SN: 20118
User avatar
RKair
Posts: 2
Joined: Thu Nov 19, 2020 11:02 am

Re: Alternator Upgrade

Post by RKair »

I have the 14-50 Plane Power STC upgrade and just removed the old VR and generator. My aircraft has a switch/CB (25 amp) labeled Generator. It seems I can hook this lead to the Output post on the Alternator and add a new Field CB (7.5 max) circuit. Or, should I change the Generator switch into a field circuit and find another place to put Output into the Main Bus?

I cannot tell from POH schematic where the Amp meter shunt is located. (Internal?) 1952 B with C-145.
User avatar
Bruce Fenstermacher
Posts: 10303
Joined: Tue Apr 23, 2002 11:24 am

Re: Alternator Upgrade

Post by Bruce Fenstermacher »

If your 14-50 is a 50 amp alternator you need a switched 50 amp breaker not a 25 amp, and you also need to make sure the power wire from the alternator to the breaker and from the breaker to the bus bar can handle 50 amps. You also need a switched field circuit which needs protection such as a switched breaker.
CAUTION - My forum posts may be worth what you paid for them!

Bruce Fenstermacher, Past President, TIC170A
Email: brucefenster at gmail.com
Post Reply