Old Piper Cherokee Starter Solenoid?

kenjr said:
Anyone know where to get a starter solenoid (the one on the firewall) for a 64 235?

There's no part number on it - assuming it's this one:

http://skywagoncity.com/index.php/piper-cherokee-140-parts/2011/10/solenoid-starter/

It sure looks the same. I can't find one of these new on the internet to save my life.
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Take it off, go down to NAPA or any auto parts store, they will match it with a new one.

These are common parts used in applications for automotive, tractors, boats, etc.
 
Check with your local mechanic he may have one on the shelf. If not go to adap.
 
RotorAndWing said:
Take it off, go down to NAPA or any auto parts store, they will match it with a new one.

These are common parts used in applications for automotive, tractors, boats, etc.
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The Marine power trim solenoid is a much better quality. and has a higher amperage rating than your auto types.
 
Tom-D said:
The Marine power trim solenoid is a much better quality. and has a higher amperage rating than your auto types.
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do you have an example of one that would be a replacement for the one in my original post? All the ones I see have 4 posts, not 3.
 
kenjr said:
do you have an example of one that would be a replacement for the one in my original post? All the ones I see have 4 posts, not 3.
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If it has four posts, one of the small ones might be internally grounded. If it is, ignore it and connect the other to the starter switch. If one isn't grounded, make a jumper wire to ground for it. The big terminals carry the starter current.

A three-terminal solenoid either has one end of its coil internally grounded, or it's a master solenoid, which has a lower-current coil in it and has one end of the coil connected to the big battery terminal. Don't use that for a starter.

Buying a used solenoid is a waste of time and money. The copper contacts inside them oxidize with age and burn with use and offer resistance to the starter current, making for sluggish cranking. Because of the high current draw of a starter, even a small resistance causes a massive voltage drop across the solenoid's contacts.

Dan
 
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kenjr said:
do you have an example of one that would be a replacement for the one in my original post? All the ones I see have 4 posts, not 3.
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your 3 post is internally grounded, the 4 post is not, one of the small posts must go to a known good ground the other to the starter switch.
 
kenjr said:
do you have an example of one that would be a replacement for the one in my original post? All the ones I see have 4 posts, not 3.
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It doesn't matter, the 4th post is just an 'I' ignition terminal that goes hot to power the coil around the ballast resistor giving it full juice during the start. If you have no need for this circuit, just don't connect anything to it and only use the 'S' terminal.
 
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Tom-D said:
your 3 post is internally grounded, the 4 post is not, one of the small posts must go to a known good ground the other to the starter switch.
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No sir, if you hook the 4th terminal to ground, you will melt a wire.
 
Henning said:
No sir, if you hook the 4th terminal to ground, you will melt a wire.
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so on those 4 posts one's - on the smaller posts where the starter connects...how do you know which post the starter connects to? I can't tell in the picture - but it doesn't appear that either of those posts are marked in any way to differentiate which is which?

We have a Concorde 440 CCA battery and now a Sky-Tec 149-NL starter that can pull from 120-180 amps. We have no intention of going and getting an older unit from a scrapyard or ebay. Just want to get the best unit for the setup we have now. We are also replacing the master solenoid attached to the battery box.

We installed the Sky-Tec and pushed the start button and the prop turned once and then we ran out of juice - starter starts clicking and the prop quits turning. We bypassed the 12v solenoid in the engine bay and that didn't fix the problem so the big problem is the master by the battery...that's easy though as we got a part number off of it. The one up front is probably original from the factory in 1964 so it definitely needs to get replaced even though it tested OK (we tested amps through it - measured same coming in as out on the posts).
 
Henning said:
No sir, if you hook the 4th terminal to ground, you will melt a wire.
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not true…

use a multimeter to determine the circuit.

some aircraft are wired so that the solenoid coil is seeking ground thru the starter switch and some are wired where the starter switch supplies power and the solenoid is grounded to the case of the solenoid.

The auto versions come both ways you must know which way your aircraft is wired before you can select a solenoid that will work.

Place a multimeter between the wire coming from the starter switch and a good ground, see if it is supplying power or is connecting the solenoid to a ground.

If it is supplying power, you need a 3 pole solenoid that is grounded internally, or provide the 4 pole solenoid a ground off the 4th pole.

If the wire going to the starter switch is connected to a ground when you hit the starter you must connect a wire from the hot side of the solenoid to one of the small poles, and the other small pole gets the wire from the starter switch.
 
ours is definitely the 3 pole version. Two big poles are in/out from the battery/starter and the 3rd smaller pole is where the push button starter switch is connected.

We'll probably just try to find one as close to that as possible just to make sure we don't screw anything up.
 
kenjr said:
so on those 4 posts one's - on the smaller posts where the starter connects...how do you know which post the starter connects to? I can't tell in the picture - but it doesn't appear that either of those posts are marked in any way to differentiate which is which?

We have a Concorde 440 CCA battery and now a Sky-Tec 149-NL starter that can pull from 120-180 amps. We have no intention of going and getting an older unit from a scrapyard or ebay. Just want to get the best unit for the setup we have now. We are also replacing the master solenoid attached to the battery box.

We installed the Sky-Tec and pushed the start button and the prop turned once and then we ran out of juice - starter starts clicking and the prop quits turning. We bypassed the 12v solenoid in the engine bay and that didn't fix the problem so the big problem is the master by the battery...that's easy though as we got a part number off of it. The one up front is probably original from the factory in 1964 so it definitely needs to get replaced even though it tested OK (we tested amps through it - measured same coming in as out on the posts).
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They are labeled "S" and "I", S goes to the starter switch, I goes to the coil or output terminal of the ballast resistor (neither of which your common aircraft engine has)
 
Tom-D said:
not true…

use a multimeter to determine the circuit.

some aircraft are wired so that the solenoid coil is seeking ground thru the starter switch and some are wired where the starter switch supplies power and the solenoid is grounded to the case of the solenoid.

The auto versions come both ways you must know which way your aircraft is wired before you can select a solenoid that will work.

Place a multimeter between the wire coming from the starter switch and a good ground, see if it is supplying power or is connecting the solenoid to a ground.

If it is supplying power, you need a 3 pole solenoid that is grounded internally, or provide the 4 pole solenoid a ground off the 4th pole.

If the wire going to the starter switch is connected to a ground when you hit the starter you must connect a wire from the hot side of the solenoid to one of the small poles, and the other small pole gets the wire from the starter switch.
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You show me an auto solenoid that grounds the switching circuit through a post.
 
kenjr said:
The one up front is probably original from the factory in 1964 so it definitely needs to get replaced even though it tested OK (we tested amps through it - measured same coming in as out on the posts).
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Ummmmm..... According to the laws of physics (as expressed by the Kirchhoff current law) , the amperage out of the solenoid contacts has to equal the amperage in (unless there is an internal short circuit to ground) - good or bad.

You could look at the voltage drop across the solenoid while cranking, but then you would need to know what the "typical" or rated drop would be.
 
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I don't think the wiring has ever been updated, in fact - pretty sure it hasn't.

It appears from this diagram that these 4 post units are not internally grounded (like the existing 3 post that I originally posted that we currently have) and so that 4th post will need to be grounded to the airframe.

One of the other partners in the plane bought one of each so we'll test it out next week once we get the other solenoid in and see what works best.
 
Silly question i'm sure, but you did make sure your battery is not only charged, but good? The way you made it sound was that this is a new battery.

Many of the older pipers have been upgraded to better starting wire systems such as the Borgert Aviation set because of this kind of thing. Just a data point
 
Capt. Geoffrey Thorpe said:
Ummmmm..... According to the laws of physics (as expressed by the Kirchhoff current law) , the amperage out of the solenoid contacts has to equal the amperage in (unless there is an internal short circuit to ground) - good or bad.

You could look at the voltage drop across the solenoid while cranking, but then you would need to know what the "typical" or rated drop would be.
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What?? The electrons don't leak and pile up in the bottom of the solenoid? :wink2:


When I take a voltage drop reading I'll reject it if I see a half-volt or so. There should be very little drop, considering that the contacts are pure copper.

AC43-13 calls for wire sizing that will limit the voltage drop for intermittent operation to one volt. Adding a half-volt drop due to a bad solenoid is like adding half again the length of cable to the circuit.

Table 11-6.


Dan
 
Dan Thomas said:
What?? The electrons don't leak and pile up in the bottom of the solenoid. Dan
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Sure thay do, that's the black stuff all over the contacts, dead electrons, they even smell dead.

I like the old Cessna master solenoid, you can take the cover off and clean it. You can close it by hand to get a battery to charge after the engine is running, and the battery voltage is too low to close it.
 
kenjr said:
ours is definitely the 3 pole version. Two big poles are in/out from the battery/starter and the 3rd smaller pole is where the push button starter switch is connected.
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These are CAR parts. Piper bought them from the same distributors who supplied car-parts stores, and considered them expendable.

Any car parts place with have them. The only difference between one 3-lug unit and another is where the switch lug is located.
 
Henning said:
They are labeled "S" and "I", S goes to the starter switch, I goes to the coil or output terminal of the ballast resistor (neither of which your common aircraft engine has)
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This is to bypass the fusible link (a big fuse) and give the most voltage to the coil during starting without risking a blown link.

An older car which starts fine then dies when the starter switch is opened is likely to have a blown link (or one disconnected by a "friend" with a weird sense of humor).
 
SoloEqs said:
This is to bypass the fusible link (a big fuse) and give the most voltage to the coil during starting without risking a blown link.

An older car which starts fine then dies when the starter switch is opened is likely to have a blown link (or one disconnected by a "friend" with a weird sense of humor).
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No, it's to bypass the ballast resistor (big resistor) that keeps you from melting the points during normal operation and give you the maximum spark power for starting.
 
Henning said:
No, it's to bypass the ballast resistor (big resistor) that keeps you from melting the points during normal operation and give you the maximum spark power for starting.
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On all the Cessna 100 series, and the Piper PA 28s it is a diode, to stop arcing of the contacts.
 
SoloEqs said:
This is to bypass the fusible link (a big fuse) and give the most voltage to the coil during starting without risking a blown link.

An older car which starts fine then dies when the starter switch is opened is likely to have a blown link (or one disconnected by a "friend" with a weird sense of humor).
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The fusible link powers all of the car's circuitry except the starter. It's just a fuse. In some cars it was (maybe still is) just a chunk of wire made from fine strands of solder or some similar low-melting-point metal. Very hard to find. It has no connection to the starter solenoid's coil, but might be found connected to the battery terminal of the solenoid along with the positive battery cable.

Like Henning says, that extra solenoid terminal was often used to bypass the ballast resistor. The coil was designed to run on about eight volts, which is what the whole system drops to during a cold start with the starter drawing so much. The ballast resistor drops the coil's supply to eight volts during normal (running) operation.

Dan
 
thanks folks. So, in our situation where we had the 3 lug with no connection to ground (assuming the solenoid was internally grounded), where do we wire up the 4th port, if we do at all? The diagram that was posted earlier shows that one lug goes to the starter and the other to ground. Are the 4 post units not grounded? Do we wire that 4th post up to the main ground in the engine bay?
 
Henning said:
No, it's to bypass the ballast resistor (big resistor) that keeps you from melting the points during normal operation and give you the maximum spark power for starting.
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. . .you may be right, this makes more sense, but my buddy had a restoration pickup that kept blowing links until one guy asked if he had a 3- or 4-screw solenoid.
 
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