Solenoids

[old bradders]

Can someone explain why I need 2 solenoids between battery and starter motor (Perkins 4108)

[Vasco]

Voltage drop

[DeepFrz]

I would be surprised if you have two solenoids. You probably have a relay and a solenoid. The relay is there because the solenoid needs a fair bit of current to activate the starter and if you draw that through your starter switch you will need pretty heavy wiring, a heavy duty switch and heavy duty contacts in all connectors to and from the battery switch. Or, like Rick says, voltage drop.

[courageous cat]

Some car like fords have two solenoids. one on the fender and one on the starter its self. Maybe a picture or decription wood help us to help you
NOW I'm starting to sound like Jerry Maguire
How long is the battery cable to first solenid, then the next cable to starter?

[boden36]

Are they both on + or is one on - ? It is possible that someone has wired solenoids into both the positive and negative sides for the feed in an effort to keep it above ground.
Regards,
Richard.

[GordMay]

Originally Posted by courageous cat

.... Maybe a picture or decription wood help us to help you ...

You shouldn't need 2 solenoids.

[Brent Swain]

I made up away to push the contacts together by hand , enabling me to use my starter when the solenoid has failed, which has been extremely helpful when it had, several times. This was common on older starters. Did the same to my spare.

[DeepFrz]

I have never seen a ford or any other car with two solenoids in the starter circuit.

What model and year was it that had two solenoids Courageous Cat?

[Blue Stocking]

Originally Posted by DeepFrz

I have never seen a ford or any other car with two solenoids in the starter circuit.

What model and year was it that had two solenoids Courageous Cat?

Go to any classic car show and look under the hood on Fords with side-oilers, or any of the old big blocks, particularly Shelby Cobras.

[GordMay]

Originally Posted by Brent Swain

I made up a way to push the contacts together by hand ...

Bravo.

[Blue Stocking]

Originally Posted by GordMay

Bravo.

Gord,

Brent is a young whippersnapper, but WE remember floor mounted mechanical push-ins, don't we?

[delmarrey]

Originally Posted by Blue Stocking

Gord,

Brent is a young whippersnapper, but WE remember floor mounted mechanical push-ins, don't we?

Do you remember when starters and generators were the same unit? You'd really be old.

Originally Posted by Deepfrz

I have never seen a ford or any other car with two solenoids in the starter circuit.

GM's had one on the fender and one externally on the starter.



Fords also had one on the fender and the other was internally built into the starter.



The old jeeps didn't have a solenoid but were manual.



Mopar's (Crysler) had gear reduction starters.



Use to rebuild all these +, after High School for a friend who owned a rebuild business.

[DeepFrz]

Go to any classic car show and look under the hood on Fords with side-oilers, or any of the old big blocks, particularly Shelby Cobras.

Okay, never been under the hood of a Shelby Cobra but I don't understand the need.

[fairbank56]

DeepFrz has it right. A remote relay is used to supply the high current required by the starter solenoid. Typically called a slave relay or solenoid as some of these are in fact solenoids. A solenoid has a movable core called a plunger while a relay does not. A typical starter solenoid requires 35 amps to engage which reduces to around 10 amps once engaged. This is too much for a start switch to handle. I believe most cars use a remote relay to power the start solenoid.

Eric

[DeepFrz]

Yes, that makes sense. I guess the difference is in the details. A small solenoid activated by the start switch to pull in the large solenoid that activates the starter itself. Have never seen it but this alternative would be more reliable than a simple relay to activate the starter solenoid. Generally solenoids are very reliable and long lived.