Magnetic Start Relay

[olverama]

Disclaimer… I did search. I am not a mechanic and therefore may not have be looking for the appropriate info while doing so.
With that out of the way… here’s the simplified version….Upon recovery of my Deuce, we threw 2 batteries in and started it up. Drove about 2 hours and stopped for fuel. When we attempted to start it back up… Nothing. After a 18 wheeler push/pull started us we were on our way. 2 ½ hours later we made it home.
We tested the batteries they were low… recharged…
Still nothing… pulled the starter and had it rebuilt… still nothing
Check batteries again still slightly low, then replaced.
Still nothing… got out the TM’s.. did trouble shooting and decided that it was the magnetic start relay.
Ordered a “known good” used one from Eastern surplus and installed… still nothing.
Trouble shot again and diagnosed it again as a bad magnetic start relay.
This is where I’m at now…

Here are a couple questions. (Again… not mechanically inclined!)
1. Can you “bench/ground/floor” test the relay? In my non mechanical brain, I feel that I should be able to pull the relay and while off the vehicle, use a pair of jumper cables off the battery (the positive connected to battery 1 and the negative connected to battery 2 (24v right?) and connect the other positive end of the cable to the terminal on the bottom of the relay. At this point, once I connect the negative to the post on the top I should get a “click” or “vibration” that the TM talks about right?
The way I’m looking at this by touching the ground/neg on the top of the relay that would be the same as me pressing the start button right? I just want to completely verify that I’ve got another bad relay.

2. 2nd question… this relay seems fairly simple.. Can I just go to my nearest FLAPS and pick up any 24v start relay and install?

 

[mistaken1]

I have not looked an the manuals: Just addressing the relay I would think you could get a new 24V coil relay. Need to make sure the power contacts are rated for the amperage they will be carrying. And I assume you want one that is fairly weather resistant.

You should be able to read open on the power contacts and then apply 24VDC to the coil and see/hear the contacts close. At that point you should see continuity through the power contacts. That being said the power contacts could still be damaged an not carry the full rated current properly.

It may be easier to use some small wire that you can attach to the coil terminals and then touch those wires to your 24VDC supply (battery) when testing relays.

 

[cranetruck]

It's a good chance that your start push button is bad. The inductive "kick" from the start relay will eventually burn up the push button contacts.
To test, just short the two wires from the start switch. That will apply 24 volts to the relay (the other side of the relay coil must be grounded, of course)

 

[gimpyrobb]

I was going to say test the start button too. Also, you described the way I would test the relay, so yes that should work.

 

[cranetruck]

To protect the start button contacts, add a diode (1N4004 er equal) as shown in the attached.

 

[olverama]

In the Marines, I am a supply and logistics guy... Im the one who gets the mechanics what they need....
Does this look right? The part number at NAPA is ST93 and is made by Echlin Ignition (their p/n is ECH ST93)
https://www.napaonline.com/Catalog/CatalogItemDetail.aspx?A=ECHST93_0215715019&An=0


here's a cut-n-paste for those of you who dont want to follow the link...
Part Number: ECH ST93
Product Line: Echlin Ignition Parts


Attributes: # Switch Terminals : 4
Contents : Hardware Package

Features and Benefits: For 24 Volt Systems, Insulated Base, Used w/ ADLO Systems, ADLO Is A Means Of De-Energizing The Cranking Motor Instantly After The Engine Starts Preventing Re-Engagement While Engine Is Running. Same Application As Listed Under ST94
NAPA Echlin Products Meet Or Exceed Original Equipment Specifications. All Products Are Top-Of-The-Line Quality, & 100% Tested & Inspected In An Environment That Is IS09000 Compliant.

 

[gimpyrobb]

Looks right, but there is no markings on it.

 

[jasonjc]

I've been running a truck for years with out that relay just fine. It came with out it and I never bothed to replace it. I was a newbe when I got the truck thought and did not know about this site. I put in a new switch and ran a wire to the starter.

 

[cranetruck]

I've been running a truck for years with out that relay just fine. It came with out it and I never bothed to replace it. I was a newbe when I got the truck thought and did not know about this site. I put in a new switch and ran a wire to the starter.

Hi Jason, consider this, the "solenoid" on the starter has two windings, one to engage the pinion gear while turning the starter motor (the winding is grounded via the motor) and one "holding" winding. The "pull-in" winding is de-energized when the solenoid relay portion closes and also begins to turn the motor at full speed.
The point is that when the start button is released, the two windings buck each other and no spike/arc (back emf) is created to harm the switch, BUT it should be rated for about 50 amps or more and the wiring to it should be about AWG 8.
If the engine starts immediately (multifuels usually do), nothing has time to get hot due to the momentary overload and you'll get away with it.

Edit: Added image

 

[dabtl]

In the world of deuce electrical systems, no one is better than Bjorn. I had a relay problem on the second deuce which was solved quickly by looking at Bjorn's many posts.

Bjorn once said that there is a reason the military put things on the deuce. They might run for a time without the thing, but eventually you will find out why it was put on originally.

Replace the relay.

 

[AMX]

My father was an automotive engineer. He once quoted an engineer for one of the big three. (Parts left off cost nothing to manufacture, require no labor to install , and never cause warranty issues). The point is that a bean counter somewhere would nix it if it wasnt needed.

 

[jasonjc]

I will replace it (some day) but I will have to replace the wireing harnes also, as who ever removed it chopped out alot of the wires also. And the wire to the cold start is fubared all so. Tryed it one time and smoke started to pour out from under the dash Good thing I don't need it here.

 

[FMJ]

I just had a start switch go bad on my Deuce last week, I checked the button first because it was easier to get to.

 

[olverama]

Success! I couldn’t find the NAPA part in stock yesterday but NAPA said that they had an alternate…it’s the Cole Hersee 24063 (pictured). It looks practically identical.
One thing that we discovered though is that will require you to ground it separately as it is insulated. We figured this out before installing it when we ground/bench/floor tested it.

We elongated the mounting holes on the relay and bolted it right onto the block where the other bracket mounted previously. For the grounding wire, we made a 2-3in wire that went from the 2nd (unused) post on top and ran it to the mounting bolt for ground. Works perfectly and only cost $29!

Thanks for all the help

 

[Ditch Baby]

mine doesnt even have on it.... nor did the one i stole my wire harness from, and the 3 i took at peak at the fire station....

 

[stancanpara]

Awesome! Good find!

 

[Katahdin]

I just had the opposite problem last night, I hit the starter button to check for hydro lock and it wouldn't stop cranking after releasing the button and killing the accessory switch. I ended up yanking the dog bone cable between the batteries to kill the starter. The starter is still drawing power after unplugging the starter switch. Could this be a bad relay as well?

I hadn't started the 109 in a couple months since I was doing body work. Starter was NOS installed in December. Batteries were new Optima red tops, fully charged, I wouldn't think it would have welded the relay into the hold-in position, but.....?

 

[steelypip]

I just had the opposite problem last night, I hit the starter button to check for hydro lock and it wouldn't stop cranking after releasing the button and killing the accessory switch. I ended up yanking the dog bone cable between the batteries to kill the starter. The starter is still drawing power after unplugging the starter switch. Could this be a bad relay as well?

I hadn't started the 109 in a couple months since I was doing body work. Starter was NOS installed in December. Batteries were new Optima red tops, fully charged, I wouldn't think it would have welded the relay into the hold-in position, but.....?

Yes, the relay could have welded its contacts together or have corrosion/whatever keeping the contactor disc from retracting away from the contacts. A quick ohmmeter test should answer the question.

 

[Katahdin]

After closer inspection I don't have the relay either, it came wired this way from GL: TN National Guard, 1985 Tooele rebuild.

I got out the ohm meter, the starter button is working as it should but solenoid contacts appear stuck together. This was a NOS starter with barely a dozen starts on it. Nuts.

 

[73m819]

After closer inspection I don't have the relay either, it came wired this way from GL: TN National Guard, 1985 Tooele rebuild.

I got out the ohm meter, the starter button is working as it should but solenoid contacts appear stuck together. This was a NOS starter with barely a dozen starts on it. Nuts.

don't buy a new starter just get a solenoid