The Stovebolt Site Forums The Shop Area The Electrical Bay alternator and engine running

I changed my alternator from an external regulator to an internal regulator, and now the engine runs on for about a minute after I turn the key off. it did not do this before I changed alternators
Truck is a 38 gmc with new drive train and Rebel wiring kit, I wired the alter. exactly the way rebel said to. so whats going on that it keeps running on after the key is turned off. I know it is some thing simple

thanks

TheShoer,

Your new internally regulated alternator has a DA plug. The terminals are marked #1 and #2. The terminal marked #1 needs to be energized as you start your rig to make the alternator begin to charge.

After your engine starts, this terminal actual begins to produce voltage. If you have wired this circuit in series with the coil in any way, and the circuit isn't broken when you turn the key OFF, the alternator will supply enough voltage to keep the ignition circuit charged and the engine will keep running.

If you have wired #1 to the coil, as is often done, you will need to install a small diode the will prevent voltage from flowing to the ignition and causing this problem. Many alternator swap kits contain a DA plug that has a small diode installed in the line near the plug.

Stuart

Jim Carter sells this
DA plug for alternators
part # HP240

It has the diode installed in line with the plug and long wire .

Pete

Thank you when I first read what you wrote Stuart I was confused, then after I thought about it for a while it hit me like a ton of bricks and made perfect sense. I was going to ask If the local parts house would carry something like that and what it was called then Pete answered my question before I could ask, Thanks Pete.

I bought my diode at radio shack and soldered it in the wire.Be sure to install it correctly,the electricity only flows one direction.

Bowtie what kind of diode would I ask for at radio shack or do you have a parts# I can ask for. The radio shack route would save me some money. Which way does the electric flow in this application from #1 or to #1

sorry double tap

I found the radio shack part number here on the stovebolt.I will go out in the garage and see if i have the part#.I checked my diode with a ohm meter to see the direction of flow.

Here is a link to the information.You will see a radio shack link by automark.Hope this helps,good luck.

radio shack diode

thanks that helps and confuses me at the same time. I'll get the diode tomorrow

there's the symbol and the markings for diodes here:
http://www.kpsec.freeuk.com/images/diocon.gif
The Cathode end on the symbol is the one with the bar across the line. This will usually be marked on the diodes you buy with something like a colored band.

The positive current will only flow in the direction Anode to Cathode, so you want the colored (Cathode) end of your diode pointing towards your alternator connection to stop the motor running on.

No harm done if you put the diode in the wrong way round first time, it's just that your alternator probably won't charge; if it does, the motor will still run on.

Stuart.