Starter solenoid recommendation

[Sparkydave]

After some preliminary checks on my dad's '47 Lincoln, I found that part of the reason the engine cranks slowly was dirty connections between the battery, solenoid, and the starter.  Now the battery terminals and the starter terminal stay cool and it's cranking faster, but the starter terminal on the solenoid still gets mighty warm after cranking for a few seconds.  The other terminal is cool.  I'm starting to think the 75 year old solenoid might be tired and it's not making good contact inside.  Unfortunately, finding a replacement could be easier said than done.  They either seem to be 12 volt solenoids masquerading as 6 volt, they have a current reading that seems way low (dad once measured 450 amps on the starter with a clamp amp), or the reviews are saying they get stuck on.  Plan B might be to start scrounging through the boxes of parts dad gave me and see if there's a starter solenoid among them, but surely these things can be found new, there are lots of Ford 6 volt tractors still out there too.

[Ray500]

The terminals are getting hot because there is resistance internally.  Probably corrosion in the contacts.  If you put a voltmeter on the output and compare it to the input of the solenoid you probably see a voltage drop which means there is resistance in the device!  Time to replace it, you can get the from Boos Harell Lincoln on line or any old Ford parts place as don't forget Ford was once 6 volts too!   Also replace the cables with 000 or what ever the heaviest gauge you can get to keep the resistance low!  You shouldn't have over a .5 volt or so drop during the starting cycle.  Your starter could be also drawing too much current. You'll need a clamp on amp meter for that one. I think mine I checked on time drew about 225 amps!

[Bloo]

The heat is a dead giveaway you have a bad connection. You can't fool mother nature (or ohms law). Power is being dissipated at that spot as heat, and that means stray resistance. There is just no way around it.

 

Yes, it could be the contact in the solenoid. can you take it apart and clean it ? Make sure it hasn't burned so much it no longer reaches whatever it is supposed to touch? Or, is it sealed and not serviceable?

 

The trouble could also be anything at that spot, like where the connector is crimped to the cable, or where the cable's connector  contacts the post, or whatever. Looking clean on the outside doesn't cut it. Imagine where the electrons are flowing. They flow through the stuff that is all clamped together with the nut, and where the cable is attached to it's connector. Dirty nuts, washers, on their surfaces that don't show, all could contribute. Clean up what you can disassemble, and if it still gets hot replace whatever you can't disassemble. I promise it will crank better.

 

[Sparkydave]

6 hours ago, Ray500 said:

The terminals are getting hot because there is resistance internally.  Probably corrosion in the contacts.  If you put a voltmeter on the output and compare it to the input of the solenoid you probably see a voltage drop which means there is resistance in the device!  Time to replace it, you can get the from Boos Harell Lincoln on line or any old Ford parts place as don't forget Ford was once 6 volts too!   Also replace the cables with 000 or what ever the heaviest gauge you can get to keep the resistance low!  You shouldn't have over a .5 volt or so drop during the starting cycle.  Your starter could be also drawing too much current. You'll need a clamp on amp meter for that one. I think mine I checked on time drew about 225 amps!

Thanks, and thanks for mentioning Boos-Herrel, I had not heard of them before and I found wiring diagrams on their website that should be very helpful.  Also turns out they are very close to where I live.

[Ray500]

One other consideration when it comes to battery cables, new fresh ones are the recommendation with the largest you can get in cable size.  Remember, you're dealing with 6 volts and higher amperage than the newer 12 volt systems in today's vehicles.  So minimum resistance is the key to effective operations.  Wires are gauged to be of sufficient size to handle the maximum current/voltage you are dealing with in your system.  And as to the termination on the connectors, you might have to solder the connector to the wire, no matter how well it looks just crimped !  Electrically if the connection of the connector to the cable is solid, then you will be able to pass the current you need for the operations.  Even in crimped connectors can have corrosion that creates resistance to voltage and current from the battery.   Easiest way to determine that is to use a simple voltmeter and follow the battery voltage through the solenoid to the starter while activating the starter solenoid to see if you're getting full 6 volts from the battery to the starter.  If at the battery during starting if the voltage is low, either charge up the battery if it's good or replace it.  I use an Optima 6 volt battery on my '41 Zephyr.  Mainly because it has gel in it and no liquid acid to lead and corrode the areas around it!   I have a battery case to cover the Optima which makes it look like a regular battery.  (Has terminal extensions too. Not sure who has those, but Chris Harrel of Boos Harrel Lincoln can help you with that one.  In the past mechanics have also put a fine layer of grease on the battery terminals to keep the corrosion minimized!   Happy cranking! 

[Sparkydave]

Thanks!  I have both an Optima 6 volt and I replaced the dead group 2 battery with a fresh one.  I like the Optima because it can't leak and has plenty of cranking current.  Since I cleaned up the connections and put the new starter solenoid in it's cranking mightily.  Good to know there's a case for the Optima.  The only downside to the Optima for me right now it's much smaller than the tray and the hold down hardware won't hold it.

[Lee H]

On 6/4/2024 at 7:23 PM, Sparkydave said:

They either seem to be 12 volt solenoids masquerading as 6 volt, they have a current reading that seems way low (dad once measured 450 amps on the starter with a clamp amp)

You’re not wrong to worry. Here’s the max. (locked) amp draw for Lincolns. It takes a lot of amps to crank a cold 6v engine. Some Packards were rated over 900 amps!

[Ray500]

I bought my Optima batter cover box a few years ago when Vintage Auto Warehouse was in business.  Check with Chris Harrel @ Boos Harrel Lincoln as he might have one or know who sells them.  It's an empty battery case and some post extensions with the Lincoln label on the side.  That way you can use the original hold down bracket to keep it in place!

 

[19tom40]

If your battery cables are more than 10 years old or have been used with a standard lead acid battery or if you don't know how old they are, I would replace them with new cables of the correct lengths and gauge from Boo-Herrel. Replace all of the cables to get the best performance. Old cables can have corrosion under the insulation that can impede current flow. I replaced the solenoid to starter cable on my 53 Lincoln this spring. It looked like new but it had a 1volt drop over its 10 inches. I cut off the insulation and the cable was green and hard under the insulation.