Re: Electrical System Frustration

Posted by HH56 On 2017/8/2 17:14:03

First thing I would do is re polarize the generator just to make sure that part is OK. With key and engine off, do the polarizing by using a decent size short piece of jumper wire and MOMENTARILY touch the ARM (GEN) and BAT terminals at the regulator together. You will get a small spark when the terminals connect. Once they connect, leave them connected for a couple of seconds and then remove the jumper wire. After that is done test the output again.

6.3v is the nominal battery standing voltage. When the engine is running at a slow idle the generator may not be putting much voltage out and that is all you will read. At a fast idle -- say 1000 rpm or so -- the generator should be delivering approx 7.4 v when measured with the voltmeter across the battery terminals.

If you speed up the engine and still only read 6.3v either the generator or regulator is not functioning properly. To test for which, connect a small jumper wire to the field FLD terminal at the regulator. You can use ordinary wire or a test clip lead which you can usually find at a hardware store in packages of 3 or 4 wires. With the voltmeter connected across the battery and engine running at a fast idle TOUCH the jumper to ground and watch the voltmeter. It should immediately jump up to at least 7.5 v. If it does not change the generator or wiring to the generator has a problem. If it does the regulator has a problem. Be sure the jumper is on the FLD terminal and not the ARM or BAT terminals. Don't leave it grounded any longer than it takes to read the measurement.

At two years the Optima should still be OK but it can fail like other batteries. If it has had issues getting charged and stayed low most of the time or has been overcharged by too much output from the charger the battery can also develop problems and may not be able to hold a charge or deliver the specified output current for very long.

With the hard starting when hot, what size are the battery cables. If they are the originals then no issues unless they are damaged. If they have been changed make sure they are at least a 0 gauge and better yet is 00 gauge. 12v cables are definitely too small and the typical modern 6v cables at the parts store -- even those labeled for 6v use -- are marginal with the large engine. Also if you have one of the battery post disconnect switches make sure it is one capable of carrying the several hundred amps the starter needs in order to turn over a large hot straight 8.