Ok....So how many of you own combines? How many of all get together and work on those combines at the same time? Ha Ha it is the two old men working on a combine story...... Oh well....Meanwhile.....
A DA plus is simple wiring harness that I designed that solves two different but related problems. First you need someway to insure the alternator will begin charging as soon the the engine is started (in other words you need to excite the fields inside of the alternator) For most modern applications this happens easily because of the magnetism stored in the rotor is designed to be released at engine idle which in this case is about 1200 rpms. Because most of our old trucks do not idle at 1200 rpms (more like 600-800 rpms) the yellow wire of the DA Plug is used to excite the fields much the same as happens in modern applications.
The second thing a DA plug wiring harness does, is allow you to turn your truck off and on with the original ignition key. Because an alternator is able to produce current at idle and low rpms, whereas the generator did not, the output from the alternator will keep the coil hot and your truck running even though you turn the key off, How embarrassing!!
The solution for GM was to introduce the "accessory" type ignition switch. The accessory post of the new design switch was isolated from the rest of the switch terminals, which stopped the flow of current to the ignition coil when the switch was turned to the off position.
I use a specially designed diode as part of my DA plug wirng harness which stop the flow of current to the ignition coil when you turn the original ignition key off. Thus you do not have to replace the original ignition key assembly to make your truck shut off. All of my dealers sell DA Plugs and they all cost the same if you buy them from me or one of my dealers.
By the way a DA Plug is not the same as the $1.50 harness that you can buy at the local auto parts store. Those do not have the diode included so if you buy one of those, you alternator may charge but it will not shut off with the key....
And nope you can't buy the same diode I use at the local radio shack store, Mine are much heavier and built to totally different specifications (mine) to last a lifetime. Radio shack diodes will last about 6 months and leave you stranded. Ask those who have been there and done that!
Finally DO NOT EVER remove the battery cable to see if an alternator is charging, the voltage spike you create will travel to the inside of your alternator and it will for sure not be charging for long. Instead all that you need to do is touch the smooth bearing surface on the back of the alternator with a screwdriver. (By the way this works for all alternators) If the alternator is charging this surface will be magnetizied. if you are unsure turn on the heater blower motor and or headlights to create an electrical load, then you will have no doubt.
Class dismissed, please pass your papers to the front, your grades will be posted on the bulletin board by Friday noon. Randy.
