Starter Relay help

I did a search and could not come up with anything. Does anyone know how to test the starter relay to see if it is bad?

The relay under the exhaust manifold, bolted to the engine?

Yes that's the one. I thought my starter went and pulled it. The starter appears to be ok. The solenoid could also be the problem. But I figured my check this first before taking the solenoid to a shop.

Use a jumper cable from one terminal to the next to bypass it and rule out the starter. (This will crank the engine, take precautions)

Good rule of thumb for vehicular starter solenoids... if it clicks it's good. If it clicks a lot (oscillation) you have a power supply problem.

You can eliminate that relay, to test if that is your problem. To do this, you can remove wire# 74 and connect it to wire #214.

That relay does fail occasionally. There are several ways/things to test.

Do you have a digital multi-meter?

doghead said:

You can eliminate that relay, to test if that is your problem. To do this, you can remove wire# 74 and connect it to wire #214.

That relay does fail occasionally. There are several ways/things to test.

Do you have a digital multi-meter?

Click to expand...

yes i have a multi meter i will check it out asap. as i said i already jumped the starter to get it going and ohm'd the push button. just dont seem to be getting juice to the solenoid

i will check all thing mentioned and report back. i didnt know if there was a fuse or something inline from the button down hidden somewhere. im sure its something simple you guys will help me figure out thats why i came here.

thanks all

I had a similar problem, OHM'd the pushbutton, it checked good. Spent another fours troubleshooting, and came back to the push button. It OHM checked good again with a different VOM when the button was pushed, so I took the two wires off, touched them together, started right up. Put the wires back on the button switch, and nothing. New starter button, and now it works again.
I don't know why it OHM'd good, but wouldn't work.

i posted that i checked voltage at push button and it was 13v dc. dont know what happend to the post
idea's
thanks

sorry it appears i posted to one of links someone put up to help me on my other thread.. please forgive me
still need some help under the thread "starter woes"
thanks guys

Forgiven. But if we're talkin about the M35A2 in your sig line, you should have 24+ VDC @ the starter pushbutton, not 13 VDC.

Old thread bump because I'm pretty sure I have a starter relay problem too.

doghead said:

You can eliminate that relay, to test if that is your problem. To do this, you can remove wire# 74 and connect it to wire #214.

That relay does fail occasionally. There are several ways/things to test.

Do you have a digital multi-meter?

Click to expand...

Hey Mr. Doghead,

Comparing the M35A2 wiring schematic and the following figure (from TM 9-2320-361-20 Technical Manual and Unit Maintenance, section 4-6, PDF page 423) it appears that wire #74R is the same as #3 and that wire #214 is the same as #18: Do you agree?


I put a digital multimeter on #3 (negative lead) and #18 (positive lead) and only got trace amounts of wildly fluctuating millivolts of difference between the two points (I believe the test was performed while the Accessory Switch was ON). When the momentary Start Switch (that I sometimes call the Start Button) was pushed, the multimeter read a full and steady ~25+v difference between the two points but I could hear no clicking from the relay and the truck did not start.

With the multimeter I ran an audio continuity test on the in-cab momentary Start Switch and the the switch appeared to be working, exactly as I expected. (There was continuity between the pins when pushed, no continuity when not pressed.) I tried a solid wire connecting the pins in the plug running up to the start button and it had no affect (did not start the truck). I think that discounts the switch as a problem.

I attached a wire with alligator clips from #3 (wire #74R) to #18 (wire #214). When I pressed the Start button the truck started exactly like normal. To me that sounds like the Magnetic Starter Relay is bad. Do you agree with my assessment?

I agree with your assessment.

Thank you very much sir! Speedy reply too!

I purchased an NOS Starter Relay from eBay, and I'm happy to report that it fixed my issue.

Prestolite
WSE-4101A

24V DC
50 Amps
Ord. No: 19207-6183391
NSN: 5945-00-636-8779
MFR: 7E656

It came with a paper that had the date "9/92" and a mylar bag with the date 8/90, so I presume it is from 1990 or 1992, but in fantastic shape. Judging by the condition of the relay I removed from my truck, I'm willing to bet it was original to the engine (1972). Being so near the engine and exhaust pipe didn't do it any favors with the numerous hot/cold cycles.



I had to replace the ring terminal end on #3 (wire #74) as its wires were exposed with a number broken. I decided to add on about 3" of additional wire.



The end of #9 (wire #14) was in similar shape (where it attached to the starter solenoid), though I felt it was still pretty sturdy. so I added some heat shrink to the end. I also used a wire wheel on a drill to clean up all of the wire's connections.

Are you going to dissect the old relay?

It might be fun to see the inside.

doghead said:

Are you going to dissect the old relay?

It might be fun to see the inside.

Click to expand...

I hadn't intended to, no. But I suppose there's some interest here that I should see how well it comes apart.

Valence said:

I hadn't intended to, no. But I suppose there's some interest here that I should see how well it comes apart.

Click to expand...

IIRC, it's not too tough to take the bottom end off. 4 screws/nuts, and it's sealed with a cork-type gasket that you might have to break loose. Once you get inside, you might just find the angled contacts are dirty. With a good cleaning, you may have a functional back-up relay. If you remove the posts, just be careful not to crack the phoenelic insulators (they look like little formica rectangles) be gentle with the post grommets and mindful of the order the post components were assembled. When you reassemble, you can seal it back up with a bit of RTV on the remaining cork mating surfaces.

I just have to do a postmortem on anything that fails like that. Inquiring minds want to know.


I just had to dissect my fuel pump and that's when I discovered it is actually a magnetic coupling between the motor and the pump section. Wouldn’t have guessed that one. Magnet came unglued from it's mount so even though the motor was spinning there was no drive to the pump section though the magnetic coupling.

Prestolite
WSE-4101A

24V DC
50 Amps
Ord. No: 19207-6183391
NSN: 5945-00-636-8779
MFR: 7E656

Wow, that is one pricey little sucker! It is only a 50A relay. Perhaps it would be a good idea to identify current alternatives for this part. Something like this could be made to fit: At $45 a bit less expensive.
https://www.amazon.com/STARTER-SOLENOID-CRAWLER-DIESEL-3T-3421/dp/B013TCQAAO/ref=sr_1_7?s=automotive&ie=UTF8&qid=1518542500&sr=1-7&keywords=24V+starter+solenoid&dpID=41wGoOlhHiL&preST=_SX300_QL70_&dpSrc=srch

Menaces Nemesis said:

IIRC, it's not too tough to take the bottom end off. 4 screws/nuts, and it's sealed with a cork-type gasket that you might have to break loose. Once you get inside, you might just find the angled contacts are dirty. With a good cleaning, you may have a functional back-up relay. If you remove the posts, just be careful not to crack the phoenelic insulators (they look like little formica rectangles) be gentle with the post grommets and mindful of the order the post components were assembled. When you reassemble, you can seal it back up with a bit of RTV on the remaining cork mating surfaces.

Click to expand...

Thank you! That'll certainly help, and I wouldn't be against having a workable backup either.

cattlerepairman said:

Prestolite
WSE-4101A

24V DC
50 Amps
Ord. No: 19207-6183391
NSN: 5945-00-636-8779
MFR: 7E656

Wow, that is one pricey little sucker! It is only a 50A relay. Perhaps it would be a good idea to identify current alternatives for this part. Something like this could be made to fit: At $45 a bit less expensive.
https://www.amazon.com/STARTER-SOLENOID-CRAWLER-DIESEL-3T-3421/dp/B013TCQAAO/ref=sr_1_7?s=automotive&ie=UTF8&qid=1518542500&sr=1-7&keywords=24V+starter+solenoid&dpID=41wGoOlhHiL&preST=_SX300_QL70_&dpSrc=srch

Click to expand...

Yeah, it is well over-priced for what it is, but I really just wanted an exact replacement. I considered buying another 100A continuous relay from Extreme Outback products like I had done for my Supplemental Electrical Air Compressors. If I need to, perhaps I'll go that route in the future and locate the relay further from the exhaust.

Sealed, 100 Amp Continuous Relay Part# 002-240, $36.95 + shipping
2A activation/control draw
NOTE: The below link is the 12v version:
https://www.extremeoutback.com/product/97/100+Amp+Relay+Part#+002-103.html



Here is a very cheap ($16), non-sealed 24V continuous 85A relay (but I wouldn't hold my breath how long this one would last):
https://www.amazon.com/gp/product/B004V3FGOC/