Cascade Crew

jchaussee · Member Joined: 14 Nov 2010 Posts: 1318 Location: renton

So I have asked for help in this area before and itvhas been quite helpful. But my issue now and has been for awhile, but I am driving it more so it is on my mind, is that my volts creep down pretty fast unless I am moving, ie under throttle. Orbison obviously worse at night because lights are on. When at idle and nothing turned on such as lights, radio, heat etc it is fine. But as soon as I turn something on it is all downhill from there. Alt good, batt good. So what is my first step to figure out problem and then go from there?

algershick · Member Joined: 05 Jan 2012 Posts: 69 Location: Kent, WA

You're absolutely sure that the battery is in good shape? My last battery needed to be replaced for about 9 months before I finally did at the beginning of the winter. Running any accessory or light function took its toll on the battery's voltage. It was so worn out that it would lose voltage and die if I didn't drive it during a 4 day long weekend. Laughing

Twilightoptics · Posted: Tue Jan 31, 2012 6:31 pm Post subject:

Need Details....

jchaussee · Member Joined: 14 Nov 2010 Posts: 1318 Location: renton

I have the big positive wire from battery going to starter. Then from starter to alt. The last problem I had was because I the ground in back to fire wall was broke. That made it so ay least revin motor would keep it charged. I tried battery from truck and did same problem. Maybe it might just be time to do the big 3 upgrade or whatever its called

Twilightoptics · Posted: Tue Jan 31, 2012 6:56 pm Post subject:

Diagnostic details....

Idle is X RPM and has X Voltage.

I turn everything on and now my RPM is X and Voltage is X.

I checked my voltage with a volt meter? Inaccurate dash gauge?

If I rev the engine to X RPM the Voltage goes up to X.

jchaussee · Member Joined: 14 Nov 2010 Posts: 1318 Location: renton

Ill get all the info tomorrow or when it stops raining, bit essentaily when I am at a light I have to keep reved to 1500 2000 just to keep 13 volts on gauge. But I will confirm volts with volt meter tomorow.

QwkTrip · Posted: Tue Jan 31, 2012 8:44 pm Post subject:

The voltage is dropping at idle because alternator cannot keep up with electrical demand at low engine speed and the extra current is coming from battery. An alternator can deliver more current at higher engine speed so the alternator catches up again when you rev up to 1500 RPM. Normally the alternator should be able to keep up at idle speed. My guess is the alternator has lost a phase and the overall charging curve is weak and "dirty". Get the alternator tested because you might need a replacement. Basically, the alternator is still working but not working well. If alternator tests good then you probably have an electrical load or high resistance short somewhere that you don't know about.

And like Paul said, use a real voltmeter for testing and don't rely on your gauge.

Alphius · Posted: Tue Jan 31, 2012 9:38 pm Post subject:

In addition, sometimes an SI series alternator even under the best of circumstances can't provide full voltage at idle.

aaron_sK · Posted: Fri Feb 03, 2012 9:35 pm Post subject:

If he has the sense wire hooked up too close to the output or not hooked up at all (which I highly suspect because this is the THIRD TIME we have been through this) then the alternator will "see" a higher voltage than the harness is actually receiving and it will cause this condition.

Dewey316 · Posted: Fri Feb 03, 2012 9:41 pm Post subject:

why are you yelling. Relax man.

jchaussee · Member Joined: 14 Nov 2010 Posts: 1318 Location: renton

It is the third time. And it has gotten better. Not it at least is drivable during day. I am wondering if my grounds are just not up to par because yeasterday I replaced one of my small grounds with a thicker gauge and it seems to be a little better. But yes I understand it is the third time, and it has gotten better just not done yet.

aaron_sK · Posted: Fri Feb 03, 2012 11:20 pm Post subject:

Resistance between battery ground and alternator case. (Any more than a trace amount = bad ground)

Termination point of sense wire. (Has been discussed but not determined)

Voltage output measured at idle at the battery. (GM dash gauges aren't worth beans)

jchaussee · Member Joined: 14 Nov 2010 Posts: 1318 Location: renton

I am going to measure volts this weekend. I don't remember what did with sence wire. It has been awhile since I messed with this issue. I drove it so little I just kind of dealt with it. My problem is that I end up over analizing he issue and think its things its not. I read something about alt pulley size so then I read more and more. But anywyas I will check volts at idle then I will turn on accessories one by one and see what it reads also

91RSVert · Posted: Sat Feb 04, 2012 6:09 am Post subject:

Also your ALT has 2 outputs.

Volts
AMPS.

Most places just test volts. Very few places test amps. Find a place that test both and have it checked out.