661 shuts off with key sometimes

[Cjclarke]

I was just reading the posts and came across the 860 wiring one where the owner was saying that his sometimes runs on after he shuts it off, but his runs like it's only one or two cylinders. Question, mine was changed to 12 volts by PO when I bought it, it has the 3 wire GM alternator, it did not have a diode or a light in the circuit, PO said he just turns key off and chokes it. I found wiring diagram from here and a number for the diode or resistor can't remember which it was called, went to my local radio shack, which was going out of business, I bought a pack of 10 diodes, along with a lot of other things as everything was 90% off. I wired it up correctly according to the diagram PO had one wire not hooked up, and installed the diode inline about 6 inches from the alternator, had it back wards first then I turned it around. I used the tractor a lot that day after that and it killed every time with the key switch. The next day I shut the key off and it stayed running, I idled it down and chocked it like the PO said he had to kill it, no big deal bad diode?!! New one in good to go...nope some times, sometimes not, it's a guess every time, I've even put some of the ones I've had installed before, same results. I might try and put a light in it next along with the diode, it has not been a problem for me, but it would be nice if it worked right. Any suggestions would be welcomed. I'm going to re wire it this spring and hook up the new 12v headlights. I have ran new wiring in the charging system, but nothing changed. It has been like this for about 5 years now.

 

[Andy Wickiser]

Are you sure it's not dieseling when you shut it off? I guess a test
might be to yank out the coil center connection (high voltage) when it
runs on and see if ignition is due to spark or hot carbon deposits.

 

[rvirgil_KS]

"I bought a pack of 10 diodes,"

Looking at Radio Shack web site, the only diodes in 10 packs were small signal diodes rated at 200 milliamp current flow, or 1/5 of an amp.

I suspect you have the wrong diode. See if you can get one rated at 3 amp @ 50 volts or anything greater than either of those ratings.

3 amp @ 50 volts means the diode is designed to pass 3 amps of current or withstand 50 volts reverse voltage without break down.

I suspect the #1 pin on Delco regulator is drawing more current than diode is designed to withstand and the diode is shorting out. If diode opens (loses internal connection) your symptom would be that the alternator would not begin to charge.

 

[Cjclarke]

No, I would say not dieseling, it will run as long and smooth as you want until you choke it. I have also checked the key switch with test light, and replaced it, but that was some time back. The weird thing is, it may work like it should many times, then it won't. Really random, I may find the reason when I rewire it, be nice to have it work all the time but not a big deal, just crossed my mind when I saw the other post mentioning kinda same issue. Thank you for the suggestion, I think it was a very good possibility. I shut the key off couple years back to talk to my mailman it kept running I throttled it down all the way, it'll idle around 350-400rpm, talked for couple minutes to him, went back to shredding for about three more hours and I went to shut it down when I got to the barn, the key had been in the off position that whole time, I choked it off, went and got my test light- no power on the field side... hmm. My son thought I had a trick to it when he borrowed it, he loaded it onto the trailer and it kept running, when he brought it back and unloaded it he idled it down and killed it with 5th gear and the brakes, then took the battery cables loose. I wasn't home when he left with it or brought it back or I'd told him about it, when I went to use it couple days later it wouldn't start. Walked down to the truck to jump it off, and cables off then I knew what happened! Gotta give him credit for taking em loose and not burning up the points. I guess he really was listening to me, took me 30 years to discover that after the teenage years, I'm sure other parents can relate. CJ

 

[rvirgil_KS]

There are 2 wires on the output side of your key switch. One supplies power to the coil, one goes to #1 pin on alternator to excite it to start charging.

Once the alternator begins charging, the diode trio in the alternator supplies 12 volt operating power to the alternator regulator. The #1 pin and the output of diode trio connect together inside the alternator.

When you turn the switch off the power from the diode trio feeds back through #1 pin to switch and on the ignition coil and the engine continues to run with switch turned off. An isolation device such as a diode, lamp, or resistor is inserted between #1 and switch to prevent run on. The diode is a one way device that blocks current from feeding back, the resistor or lamp limit feed back current to a level below what is required to operate the ignition.

 

[Cjclarke]

This wasn't a made by radio shack 10 pack, I guess I should explain. They were closing our store here in Palestine, Tx. and they had items on sale packaged up with like items. Everything was 90% off this was a Saturday they were done by Monday they were selling the shelves, racks, the bins, even the telephone and the time clock. I had got the number for them off here somewhere when I searched. I called the RShk and they said they had em and would hold em for me but I would have to buy them all , no singles I said ok, I never bought any electronic stuff before and after I told him I'll take em be there Saturday, I hung up, and thought I have no idea how many they have and how much they cost. I called back, no answer. I showed up Saturday expecting to drain my bank account, to my surprise I had make two trips to the truck, with the fella carrying things with me, prolly didn't spend $30 for everything. Toggle switches, rolls of wire, heat shrink tubes, solder gun, solder, etc. Sorry for rambling, when I told him the part number he checked and said he had it, but I never checked, so I have the ziplock bag with all of em in the barn I'll go see what the number is and I'll report back. If I remember they were in individual bags of 1 or 2 ea. been awhile since I looked at em. That maybe my problem I have the wrong size. Thank you if it is or isn't, for the help.
CJ

 

[Cjclarke]

If I did have too small of diode and it shorted out, would it reset itself like a breaker, cause it will shut off sometimes and not sometimes, crapshoot when you turn the key.

 

[Cjclarke]

I don't know how to post a picture of the package but the part number is 276-1661
Pkg. of 4
It has all the specs on the back
V rm (rep) V fm (wkg) 50VPK
V rm (non-rep: 100V
V r 35V
I o 6 amps @ 60*C
I r 25uAdc
I fm(surge): 400APK
Tj T ?? -65 to +175*C
Q i a : -30*C/watt
Electrical characteristics
V f (AV) .9VPK
I r (AV) 25uAdc

Rectifier Diodes
Is this the right ones? I have 8 paks of 4 unopened and 3 just loose all the paks say the same and the loose ones have the same markings as the others...6AO5 1411 .
I know the stripe has to do with the direction, when I put the first one on few years back, I had It backwards and turned it around and worked great for a day and a half, next day on kinda hit miss, just started it now and shut off with the key, but couple weeks back last time I used it I had to choke it to kill it. Well I idle it all the way down and use high gear and the brakes now so as not to foul the plugs.

 

[rvirgil_KS]

276-1661 are my favorite diodes for this application. Big healthy leads that are rugged and easy to work with. Not likely that a diode would intermittent short. Did you say you are going to rewire the tractor? You found a bargain!

band on the diode goes toward the alternator pin #1

I assume you have checked that there are no stray wire strands shorting across the diode.

 

[JDEM]

Diode cannot reset itself. It either works or it does not. When it blows -it blows like a fuse and will pass not current
either direction.

Delco 10SI or 12SI can draw up to 4 amps of field current. So any diode 6 amps or bigger will work. I have never yet in my
life heard of a diode going bad by all of a sudden passing current both ways. When they blow - they blow wide open.

You can avoid the diode thing if wanted by installing a standard automotive-type ignition switch. Just hook the exciter wire
to ACC and use IGN for anything else that needs power when the key is on.

 

[Cjclarke]

Thank you all for the feedback and the answers, I checked and I have the band in the right direction, no stray conductors that I can see, I did however use crimp connections first butt splice, when it didn't shut off the first time I changed the diode I put male and female spade terminals on and soldered them I've got it to where I could take the diode out and put the wires back together. I also put some heat shrink over it for weather proofing and vibrating loose. Yes, I will replace all the wiring on the tractor including these with the diode in it now. The original wiring is really stiff in places and really just needs to be redone. I have different colors for different circuits and the correct gauges for them. I will prolly find the problem then. Or at least end up repairing the problem and not having known what or where it was. If I do see what is causing the problem I'll report back. I didn't think they had the capability to short out then reset themselves, but I never thought I'd be typing on a phone either, I grew up with a rotary phone on a party line. The wiring I can do and I can replace the diodes and such, just wasn't sure what It does or how it does. Wonder if it'd be ok to put a little light in the dashboard for the same purpose and still have the diode too, when I redo it, or is that a bad idea. The diagram I have showed both but I know it was use this or that not have both.

 

[David G]

You sure it is not just Dieseling after you shut the key off?