Electrical Gremlin Stomped!

["therealdmcvegas" <DMCVegas@xxxx>]

For a while now, I've had an intermidant problem with low voltage 
when the A/C is running. This has been a pain to diagnose, and has 
driven me crazy! But now, I have solved this little electrical 
gremlin!

The situation is this: Sometimes when running the A/C, the voltage 
will drop down to almost the 2nd line on the voltmeter. I can get it 
to go a little farther if I turn the headlights on, and the blower 
motor up. I've also noticed that as I tax the electrical system 
further, the tachometer needle will rise. And as told to me on the 
list by others, this is a sign of an electrical problem. All of my 
ground connections, and every single electrical connection I've been 
able to reach I've cleaned. Another problem is whenever this problem 
occurs, accelleration from a stop is sluggish. But the oddest part 
has been that this issue only occurs intermidantly. And another item 
is that with the A/C off, the idle would be around 11-1200 RPM's. 
With it on, the idle would drop to about 900-950, and the voltage 
would drop. But when the problem didn't occur, the idle would stick @ 
950 reguardless, and there wouldn't be as severe a power drop. The 
needle would move, but wouldn't drop below 13V on the voltmeter.

But I have finally diagnosed the issue. A sticky throttle cable!

Recently, I've been troubleshooting an unrelated problem with bad gas 
milage, and noticed that as the summer has progressivly gotten 
hotter, the throttle cable has begun sticking @ 23-2400 RPM's, and 
would drop to about 15-1600 with the A/C on. A quick slap of the 
throttle pedal, and the idle would drop to 950 RPM's, and the voltage 
would stay normal. Previously, I thought I had an electrical problem 
with the A/C clutch because it wasn't until the A/C was engaged that 
the voltage level dropped when the issue occured. When I next had the 
problem with the low voltage, I started playing with the window 
switches, and saw that with all accessories on, and both switches 
depressed, I could get the tach to jump and read almost 1500. Turning 
the A/C off, all became normal, except the idle speed hit 1200. Out 
of frustration, I slapped the gas pedal, and the idle returned to 
normal speed, and when the A/C turned back on, I had full power to 
the system! I've tested this a few more times when the problem has 
occured, and I've confirmed it.

The sticking throttle cable was not allowing the throttle spool to 
return fully, thus not tripping the idle speed microswitch. When the 
A/C was on, the both the idle & voltage dropped because of the extra 
load on the engine. Low idle = low voltage because the alternator 
wasn't spinning fast enough to put out enough power to sustain the 
system. Because of a low voltage situation, the tach wasn't able to 
give a correct reading, and was falsely reporting back an incorrect 
idle speed that was faster than it really was. A bit of a vicious 
cycle, but one that I've finally figured out!

I don't think that this is going to be a common occurance with most 
people here. Usually a low power @ idle situation is due to dirty 
ground connections. But just in case, I thought I'd share this with 
everyone to help them out in the future.

-Robert
vin 6585 "X"