Have searched until blind with no luck. Need the brain trust help on this one.
130 amp CS130 alternator with sensing wire installed and proper resistor/diode installed on 'L' wire due to no warning light.

All of a sudden engine-running voltages at ignition switch and fuel pump reported by TunerPro are much higher than voltage across battery with known good DVM. Observations:

• Alternator checks OK off-car on machine (although not at operating temp)
• Idling ripple voltage test across battery provides constant AC voltage of 60 millivolts so OK
• If turn on 30-40 amp stereo amplifier at any RPM, TunerPro voltage rises from 13.6 to 14.5-16v, but battery volts remain at 13.6
• The battery voltage across the battery remains constant with or without load

Prior to this, TPro and voltage across battery were always the same.

 

Check the power and ground circuits for the ECM. Check them at the ECM while they are under a load. If that checks out and the values being reported by the ECM are still completely different I would conclude the ECM has failed.

GD

 

In the days ahead, I plan to run voltage drop tests + what you described. However, I've put 7730s through all manner of electrical hell and never a failure. Plus, all other data reporting is perfect. Not in the original post, but the dash voltage gauge is also reporting the voltage increase. Seems that would be receiving voltage from the alternator exciter wire which is also likely feeding the ECM. Don't know without chasing it. Also strange that 2 separate ECM inputs would fail (Pin A6 ignition switch and Pin E13 pump), with all other inupts being OK. But then anything's possible. In the mean time, I'm still struggling with what would cause a voltage increase with increased load. Seems backwards. Anyone have ideas about that?

 

Gut feel is a feed back loop in the ALT is adjusting voltage during the increased load it sees. I know nothing about how alternators work for the record, but it seems they need to provide an output based on load, and it may be potentially over compensating. Is 14V too much? Seems like the tolerances of our cars would be pretty wide ranging, like 11-14 volts would be acceptable range. maybe 14 too high, but 13 ????

 

I don't know what are the accessory terminals of a cs130, but if it truly does have a voltage sense terminal (S), then it is regulating voltage to wherever you connected that wire. If that location goes voltage low then the alternator will lift charging voltage to bring that location up to the voltage regulator set point.

Either way, it seems some of your grounds are not actually at chassis ground and is probably the cause of your problems.

 

As far as I know, voltage you be approx the same at every point in system with some variation due to resistance and impedance. But the alt should regulate loads appropriately.

 

Regulate meaning producing more power/wattage available for the entire system to use. Each subsystem will only use what it needs.

 

Voltage is just an electrical potential between two points and can be different depending where you measure it.

The alternator will try to create about 14 volts against the reference point (where the S terminal is connected) and it's frame. Funky things can happen when either of those points aren't what they're supposed to be.

An alternator regulates voltage, not current. The current just is what it is until the alternator can't give anymore and then voltage will go low (below battery open circuit voltage).

 

If the dash gauge is also affected then that entirely changes my recommendation for diagnostics. I would be looking for a bad connection. Since you are seeing a different voltage at the battery than at the volt meter and ECM I would be checking the battery terminal connections. A voltage drop from the posts to the terminals may cause the alternator to "see" a lower voltage from the battery on it's S terminal and cause the regulator to jack up the system voltage to attempt to correct for the sensed lower voltage. I would trace the S terminal feed (verifying that it's seeing lower voltage) back to it's origin and find your bad connection.

GD

 

Thanks for all the input. Progress so far:

• All voltage drops < 0.1v so wiring and connections appear OK
• Started car and while cold and warming up to 150*F or so, all voltages normal with and without accessory load while idling and at 1500-2000 RPM
• Started driving to operating temp. Shortly after at temp, problem arose with high voltages at pump and ignition switch
• Stopped car. Problem still occurring. Good voltage across battery, high switch and pump.. Removed PFLS connector from alternator and ALL voltages 11.9-12v as expected since all voltage coming directly from battery
• Ripple AC test while cold and hot does not show any irregularities (60ma steady).so diodes OK

So it seems issue has to be:

• Voltage regulator malfunctioning at high temp causing high current on L wire to voltage gauge where high voltage is also seen
• Bad connections (wire crimps) on either S or L wire causing bad connection either with heat or vibration while driving

Any others you can think of?

What about L wire operation? I thought current on that wire was provided from 12v source TO alternator to excite it. Does the alternator send any voltage back on that wire from the alternator? Have searched without luck. Am an electrical "igit".

When engine cools down, will chase L and S wiring for bad connections..

 

Problem appears to be solved. Only more logging will confirm.
Chased S & L wires from alternator to termination. All connections and butt connectors solid.
So on a lark while problem was occurring, pressed hard on the alt PLFS connector and bingo, problem disappeared – normal voltages!!! Logged 20 minute drive and all good. So I clearly have an alternator with a retracting pin(s), or a connector with improper/loose connections not properly grabbing alternator pins. When the beast cools down, I’ll investigate both. I hate electrical!!!

But still would like to understand why a possibly less than solid connection on S or L wire or both would cause higher voltages. If anything, seems the voltage would be lower as when removing the connector altogether.

Any ideas?

Again, thanks for all the help.
T

 

Through all the trials I have had with CS130 alternators..... I have come to the unfortunate conclusion that there are NO GOOD PARTS including the voltage regulators currently being manufactured for the CS130. They are ALL junk due to none of the major quality manufacturers seeing a viable market for CS130 components. Your best bet is to go to a modified LS alternator designed for CS130 fitment. DC Power Engineering and Mechman both make quality units of this type. I have a 180A modified alternator with a CS130 fitment billet front cover that works amazing.

But yeah the CS130 is a dead platform.

GD

 

The wire from the S terminal is connected to some location in your electrical system that has voltage. The alternator observes the voltage applied at the S terminal and continually adjusts charging voltage until the S terminal reaches whatever is the voltage regulator set point (about 14V). In your case, the resistance in the sense wire (poor connection in plug) caused some voltage drop, and the alternator saw something less than 14V at the S terminal. So the alternator reacted by raising system voltage until it saw 14V at the S terminal.

For example: Let's say you have 14V where the wire is tied to the car's electrical system, but there is a 2V loss across the loose/poor connection at the alternator. The alternator will only see 12V at the S terminal and try to lift system voltage +2V. The alternator thinks it's regulating to 14V, but the electrical system is actually at 16V.

If connection to the S terminal is lost altogether (no voltage applied), then I'm guessing that the alternator will ignore the S terminal voltage and just regulate to 14V across it's own electrical terminals. That's probably where you got the 13.xx measurement at the battery.

And if the L terminal is lost, then I suspect the alternator shuts off and system voltage will drop to whatever the battery can support (something less than 12.5V)

Again, I'm not familiar with the CS130 but that is likely how it works.

 

Again, thanks for all the input. And GD, truer words were never spoken. Also I now truly know that success is a fleeting thing. Went for a logging drive this afternoon and after 30 min all OK, but pull into the driveway, and TPro showing higher voltages -- but not to the prior extreme. Matters not, new alternator will be installed. Voltage regulator has to be being affected by heat because the PFLS connector was solid because strapped down;Stay tuned and thanks to all!