• Hello there guest and Welcome to The #1 Classic Mustang forum!
    To gain full access you must Register. Registration is free and it takes only a few moments to complete.
    Already a member? Login here then!

Solenoid delete theory

Sluggo

Sluggo

Active Member
On top of the other upgrades I'm performing on my car, I've become obsessed with eliminating the original solenoid.

I'm running a mini starter already which has it's own solenoid.

I thinking that I can wire a 40 amp 5 lug relay with dual 87 outputs to replace it.
Terminal 86 to ground
Terminal 85 to start wire from old solenoid
Terminal 30 to battery positive with a 30 fuse
Terminal 87 to mini starter solenoid
Terminal 87(2) to ignition wire from old solenoid
2 gauge wire from starter to battery

Can anyone think of any reason this will not work?
 
StarterRelay.jpg
 
"RyanG85" said:
StarterRelay.jpg
Click to expand...

That's almost exactly what I'm doing except 87a will be a second 87 and will energize along with the primary 87 to give the coil the same momentary 12v that the original solenoid would for easier starting. 85 and 86 are reversed in the diagram also. I don't think it matters which way the control circuit is wired unless there is a resister in the relay.

I'm going to go with it. Don't see how it cant work. A relay failure is probably less likely than a solenoid failure and toting a spare is easy enough. If it were to fail, simply plug in the spare with no tools required.
 
exactly! Doing the same with my 65. I've been through 3 old style solenoids in my 69 in the past 5 or 6 years. I'm thinking the failure rate on the relay vs. solenoid would be alot less.
 
Life expectancy of the relay is supposedly in excess of 100,00 cycles. I'm no genius but I'm pretty sure the old school solenoid can't compare. I think the big killer of the old solenoids is low battery voltage. The relay won't operate below 8 volts. Not much chance of it welding itself together.
 
So are the 2 - 87's needed to replace the I and S on the solenoid? Just wondering do you only need one if you're not running points?

I think I'll go this route too since moving my solenoid to, the trunk and planning on installing a mini starter. As you've said, a lot easier to change out with a plug in pigtail. Only one bolt hole needed to attach the relay and no need to ground like the 2 solenoid mounts.
Jon
 
Isn't 87a a NC contact with no power applied to the coil? If so than when power is applied it will open and 87 will close.
 
He's looking at a relay that has two 87 outputs... The 87a would not be used. I'm curious as to how available the dual 87 output relays are.
 
"Sluggo" said:
That's almost exactly what I'm doing except 87a will be a second 87 and will energize along with the primary 87 to give the coil the same momentary 12v that the original solenoid would for easier starting. 85 and 86 are reversed in the diagram also. I don't think it matters which way the control circuit is wired unless there is a resister in the relay.

I'm going to go with it. Don't see how it cant work. A relay failure is probably less likely than a solenoid failure and toting a spare is easy enough. If it were to fail, simply plug in the spare with no tools required.
Click to expand...

You are on the right track, but keep 85/86 correct in polarity. Dual output relays are common parts in most help sections, mostly used for aux lamp contol.
 
Re: Re: Solenoid delete theory

"stangg" said:
He's looking at a relay that has two 87 outputs... The 87a would not be used. I'm curious as to how available the dual 87 output relays are.
Click to expand...

OK, Thanks I didn't catch that at first and scanned over the drawing.
 
"Jonk67" said:
So are the 2 - 87's needed to replace the I and S on the solenoid? Just wondering do you only need one if you're not running points?
Click to expand...

May not be necessary. I'm running a unitlite dizzy. Not sure if I need the (I)signal or not but I'm going to keep it in the circuit since it does not cause any problems. It only applies added voltage to the coil when the key is in start position.
 
It does indeed work. I did not start the car because the oil gauge is disconnected. I did give 'er a bump and it worked as planned.
 
I was looking to post this exact scenario, but found this thread. Just wanted to inquire on how this setup is working for those that have implemented it. Has anybody measured the draw the start mounted solenoids draws? Is a standard Bosch 20/30 amp relay good enough?

Rob
 
"rv345" said:
I was looking to post this exact scenario, but found this thread. Just wanted to inquire on how this setup is working for those that have implemented it. Has anybody measured the draw the start mounted solenoids draws? Is a standard Bosch 20/30 amp relay good enough?

Rob
Click to expand...

I'm running a 30. Probably 40+ starts so far. No issues. The solenoid on the mini starter is handling the high amperage. Relay just passing along 12 volts.
 
Is the above posted schematic good to go?

Sluggo: Did you run the double 87 relay? I will be doing this mod as soon as I get my mini starter.
 
"65coupei6" said:
Is the above posted schematic good to go?

Sluggo: Did you run the double 87 relay? I will be doing this mod as soon as I get my mini starter.
Click to expand...

I did run a double 87 but discovered that hooking the I wire up to the second 87 caused a feedback issue through the ignition. The car would start and die. If you decide to do this mod, just leave the I wire disconnected.
 
You must log in or register to reply here.
Back
Top