Topic: Relays

[74750k4]

Anyone use a relay on the starter solenoid? I had a failure yesterday. Need to investigate to find the cause. Could be the solenoid, starter switch, sfety unit, or maybe buffing bullets. That seems to be a cure all...   bullet buffing. But anyway, it might be a good mod to have a relay for the starter solenoid.

[phil71]

The starter solenoid IS a relay.  If you disassemble it, you'll find a large copper bar, attached to a plunger that is pulled by an electromagnet. The bar then connects the two large terminals. If it's clicking, but you have intermittent or no action at the starter, you may find lots of corrosion on that bar and the terminals it contacts. Even if it's not corroded, sometimes divots get worn into that bar, and the uneven contact creates more heat , then the problem gets exponentially worse and deterioration happens faster. In either case, once disassembled (not hard to do) often you can sand a new flat surface onto that copper bar, clean the large terminals, pack a little dielectric grease in there and be good to go. Be sure to carefully open the strain relief so you can slide the black & yellow/red wires through as you separate the halves.

[74750k4]

Why yes...  of course. A very heavy duty relay, no question, except how much current is drawn by the solenoid coil? Enough to arc/burn out the starter switch? Which is the reason I am asking if anyone uses a relay to drive thhat heavy duty relay called a solenoid.

[74750k4]

"To overcome this (solenoid coil current) limitation, a relay was used to remotely switch the solenoid. Indeed, the first relay fitted to MGB's was for this very purpose."
http://faculty.ccp.edu/faculty/dreed/AT121/at121files/relays.htm



"The most common problem with the starter circuit in relation to
the starter not cranking can usually be traced via the wiring.
The circuit consists of a long run that extends from the bat-
tery, which sits in the rear of the car, to the ignition
switch, located in the front of the car, and back to the star-
ter. Old wires, dirty electrical connections or a weak ignition
switch can all contribute to the solenoid not receiving ade-
quate current in order to energize. The hard start relay re-
duces the normal 20-30 amp draw of the solenoid to under 1 amp
eliminating all of these variables. "

http://www.wolfsburgwest.com/wired/wired_03_01/wired_03_01.htm

[shark]

I do not have a relay for the starter solenoid on  the bike.

However, I have this on my car:

http://www.madelectrical.com/catalog/st-1.shtml

76 cutlass with headers, starter wouldn't work when hot, this fixed it.

My truck had a kill switch that interrupted power to the starter solenoid using a relay. Between a intermittent problem with the starter and the fact that it is a stick shift that you can catch in gear to start, I disconnected it.

[74750k4]

Yep, high current solenoid coils, long wires, bad starter switch contacts all add up to a big weak signal at the solenoid.
Hey, just noticed HondaMan has all kinds of relay saver kits on his site!

http://sohc4shop.com/catalog/index.php?cPath=23

[phil71]

Shark, the old "GM hot start" problem is a pain .. that kit is a great way to sort it out for sure! These bikes don't have ambient heat to contend with.


the starter button's pin to ground is more than adequate to supply the amperage the solenoid needs. Sure, it would be good to home run a new wire, and clean up the hold down and plunger pin in the switch, but it was good enough for honda 40 years ago, and has lasted this long. But again if you already knew you were going to do this, why ask?

[74750k4]

I am??? It might be a good upgrade though, thanks for suggesting it!

[74750k4]

If you remember correctly, all the wiring you need for an added relay is right there at the solenoid...

Switch wire, Battery B+ wire, and nearby ground. No home run necessary. Hook up relay n' go!

[phil71]

You've been snarky to every answer anyone here has offered on multiple threads, and then called them stupid. If you want to put relays everywhere, by all means go ahead. If you're looking for someone to talk you out of it, I can only think of two caveats. 1) a bit more current draw over stock. 2) more troubleshooting steps if anything should go awry.

[74750k4]

Sorry if I somehow offended you. That was never an intent. Always open to all opinion, and usable information. I don't recall calling anyone a name. If I did, I apologize profusely.

[lucky]

How many are using them? Are they a reliable solution, or just one more part to go bad???

The purpose of a relay is to keep heavy current from flowing through a small switch.

[74750k4]

Yes, my small switch for the starter relay coil seems like it may have failed. Bigger switch, or adding a smaller relay to drive the solenoid coil may improve that in the future.
At any rate I found this post:
 
http://forums.sohc4.net/index.php?topic=80532.0%C2%A0

that describes all the work involved in burnishing those starter switch contacts. Here's the circuit showing the various components involved in getting the solenoid to close. In my case, it closes if I ground yel/red wire. Suspiciously sounds like switch contacts failed from that air gap arc.

[lucky]

I personally find knowing more, is discovering just how very little we actually do know. The amount of undiscovered realities is far greater than the sum of all our collective revelations. It's fun to learn, and that is what makes, and keeps life interesting! So anyone who says they know it all, surely is one.

"So anyone who says they know it all, surely is one." Is one what???


BTW.....  You are right in some respects about knowledge.
Engineers did not discover which way electrons flow in a battery until about 1957.
There were several positive ground cars in production.
The british MGA is one.

[74750k4]

Yes, and still trying to figure out if magnetism is related to gravity or not. Somebody who knows more than we do, or so they say. I'm happy just to be here to learn what I can.

[74750k4]

Just saw your post regarding the starter motor safety unit. You obviously have a good amount of curiosity to dig that PCB out of the potting. Schematic posted for it too.

http://forums.sohc4.net/index.php?topic=99117.0

[74750k4]

Turns out the starter switch contacts are just fine...  however, the yel/red wire was broken off the solder connection right at the switch...  a bit burned too. resoldered, a bit of burnishing, and VOILA! She starts at the grips once again!

[bollingball]

Damn this whole thread started to sound familiar. I have a back up to a back up for the primary. But they are all 45acp It is easier than you think to cc three at a time.
Ken

[74750k4]

http://www.overunity.com/9875/understanding-the-sparks-created-when-using-a-relay-to-switch-a-coil/

The Starter solenoid control coil is about 3.1 ohms 11 mH. Roughly 4 Amps drawn through the starter button...  and a wallop of a spark when releasing, and getting that nice big inductive kick, that arcs across the contacts.


 http://www.electro-tech-online.com/general-electronics-chat/97329-relay-diode-back-emf-new-twist-2.html

[phil71]

it's true. They only seem to work well for about 41 years, and then they need some looking after. What a bad design.

[74750k4]

Horrible   and we're helping all those 41 year olds to the best of our abilities!

[phil71]

I'm 41. My K1 is my age, and holding up better. My starter button is a lot slower than it used to be.