solenoid rebuild


Old 09-17-09, 04:43 PM
Thread Starter
Join Date: Jun 2009
Location: Virginia, USA
Posts: 45
solenoid rebuild

thought i'd share this for those that are cheap like i am and like repairing their machinery themselves

i've had some extra time on my hands transitting into retirement, and i had a starter & solenoid for a honda 3813 that were "bad".

i pulled the starter down for the heck of it and it was far simpler that i'd thought, and the problem was easy to diagnose and repair - but i'll save that for another thread if anyone's interested

the solenoid, - i'd never pulled one apart and was curious to see what had failed and if it was repairable (honda charges $60 for this solenoid) - i have replaced my orig solenoid years ago with a $7 ford type solenoid from autozone but it didn't mount on the starter like the orig

anyway, turns out it's fairly simple

the top edge of the body is stamped or crimp folded over the plastic pc with the two lug posts & the spade connection - i noticed under the spade connection the crimped edge had a gap (appeared like it was left like that on purpose, to faciliate removing) - see upper red highlite arrow in pix below, and there's a spot crimp that i suspected would need to be drilled out - see lower red arrow

next shot i've got a small screwdriver started in that gap under the spade connector and with a 4 oz hammer i've tapped it a little around the crimped edge

below, i've finished tapping the screwdriver around to bend the crimped edge back, and after this photo i went around that same edge with the screwdriver just inserting it and bending that edge out a little more till it was obviously bent back far enough for the plastic body to come out. It really was fairly easy to "uncrimp" that rolled edge

in the next shot i took it apart (and yes, that small round crimp had to be drilled out - try to do it on a drill press and use the stops on your chuck's travel so it can't penetrate thru the crimp very far

found the reason the solenoid wasn't working - the lead to the spade connector was broken - really wasn't a very thick lead, by eye a 18 ga wire at most and maybe only 20 - 22 gauge - (the arrow is pointing to the insulator it travels thru and unfortunately the camera didn't focus on that insulator - there's a better shot of that insulator coming up

in the next shot, i've got the contact plunger held up by a screwdriver just to demostrate it travels upward - it's spring loaded into the retracted position, retracted into the center of the copper wound spool which is apparently an electromagnet, that when it goes hot from the current from the spade connector, it forces that plunger up, and that copper bar you see over the screwdriver comes in contact with the the underside of the two screw posts on the plastic top body. Basically it's doing under the plastic body what mechanics do with a screwdriver shorting across the threaded lug posts when they're trying to determine if it's the solenoid or the starter when an engine won't turn over. Remember, it's a fairly heavy guage lead coming from the starter going to one of those threaded posts on top of the solenoid. The spade connection has a lead going to the "start" position on your ignition switch on the dash, so when you turn the key to "start" you're energizing the electromagnet to lifting the contact bar and completing the circuit from the lead with the cable from the positive post on the battery, over to the post leading to the starter, engergizing it and causing it to turn.

in the next shot, i've removed the nut & washer from one of the lug posts and it just pushed out - i'll clean it with some emory cloth and wipe the threaded post side with some silicone grease before reassembling

in the next shot, i've pulled the yellow strip of tape that was holding the wound wire and unwrapped one coil's length and pulled it thru the insulator
- there's more than i'll need but i'll cut it tomorrow when i get ready to attach it back to the broken lead or the underside of that spade connector -

i had a little concern that the solder will melt the plastic around that female opening under the spade - it looks like it was soldered BEFORE with the wire pulled thru the plastic top, then the spade's lug was pulled thru and expanded to tighten it's fit to the plastic body - that would explain the insulator being so oversized to the wire (you could easily pull 4 more leads thru it) and then the excess wire was pulled back to the coil side of the spool flange & wound around the coil and that yellow tape was placed on it to keep it from coming loose and feeding back up thru the insulator - they probably cut the wire to a predetermined length before soldering so they could make one complete winding around the spool after soldering -

well, the patient survived the autopsy. Found an old 25 watt pencil soldering iron in the back of the shop, and a spool of thin rosin core solder, it flowed real nicely without melting the plastic -
total time investment somewhere in the area of 45 minutes but it was more the "satisfying my curiousity" factor that made it worth while

re-assembled and tapped the edge back into the plastic body - that metal was really soft as it folded over real easily from taps from a 4 oz hammer. i then took a small blunt chisel and used it to help that edge cleat into the plastic body or at least pull as tight to the plastic as possible - the plastic was just pliable enough that it would deflect in some with each tap so the edge folded over pretty tight to the body. it doesn't look like a factory job but i'm sure they used a die to swage that edge over - there is an O ring gasket under that plastic body so the unit is fairly weather/dust tight, and the small circular crimp that i drilled out, i cleaned the inside burr, and once assembled plugged it with some black silicone

took a battery, grounded it to the metal table top, hooked up a starter switch from positive side of battery to the spade connection, (solenoid was grounding thru it's body in contact with the metal table, and had an interesting reaction - the action of the plunger traveling upward would cause the solenoid to jump vertically off the table, lose it's ground allowing plunger to retract, then fall back contacting table only to make circuit again, jump again, etc, but it was repeating that sequence so fast it was like the staccato of a mini-machine gun

anyway - for the 15 minutes it took to take apart & inspect, it's well worth taking your solenoid apart to see what the failure is before buying one, even one of the inexepensive ford solenoids - the time it would take to go by Auto Zone, you could have the original solenoid off and back on the starter

hopefully this helps some better understand how their lawn tractor works and how to perform surgery on their solenoid

I posted this thread and a starter teardown/rebuild thread in a honda forum, and it seems there are a lot of folks like myself that had never taken either apart - if there's interest, i'll post the starter thread as well - most starters are identical in fabicration & design, so it's info that is transferable to other starter makes

and btw, the honda uses a nippondenso starter, that from honda is $384 - - did a google for nippondenso and found a distributor in california with the exact same starter (from the starter's part number on nippondenso's plate) and price, retail, was $96
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Old 09-17-09, 04:49 PM
Thread Starter
Join Date: Jun 2009
Location: Virginia, USA
Posts: 45
forgot - last shot assembled

Old 09-17-09, 09:07 PM
cheese's Avatar
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Join Date: Jul 2001
Location: USA
Posts: 16,819
I've thought about taking some of those kawasaki solenoids apart...some of them are over $100. If mine ever goes bad, I'll probably do it. (john deere LX188...I think a solenoid for it runs ~$90). A lot of things are repairable but they get replaced instead for lack of time, ingenuity, and or knowledge. Good job.
Old 09-17-09, 09:33 PM
michaeljp86's Avatar
Join Date: May 2005
Location: USA
Posts: 478
Nice job, I fixed one on a white, it lasted about a year before it went bad again. A new one was only $15.

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