97 psd alternator?

[Crumm]

Battery recharge would explain it. I just started my truck up at work. It is a nice warm -42 degree morning. After the glow plugs turned off the guage didn't get up to its normal running position for several minutes. The truck had not been run for about 36 hours so I just assumed like you do that the batteries were recharging. When I am parked inside the guage jumps right up to its normal position right after the plugs shut off.

 

[dieselweasel]

The delay shown in the charging is NOT directly due to the glow plug circuit. It is due to two features of the regulator control circuit, Soft Start Delay (SSD) and Load Response Control (LRC).

The SSD is programmed with a delay time to keep the alternator from increasing the torque necessary for the starter to turnover the engine. It also protects the glowplug circuit from a spike/surge when transitioning from battery power to alternator power.

After the SSD is finished, the LRC will gradually phase in the current from the alternator, based on its current output.

I'll point out that the SSD and LRC behave very consistently, regardless of the temperature of the engine. However, the glow plug activation time IS dependent on temperature, with the time decreasing as the temperature increases to full operating level. The only variation in the regulator output is that increasing the idle RPM above normal will more quickly raise the voltage to max, because normal idle RPM doesn't let the alternator produce an output high enough to power the glow plug circuit and recharge the batteries after cranking without sagging below max voltage for a while. Once the glow plugs are deactivated and the batteries have bulk-charged, you'll see the voltage raise to the max level.

dieselweasel - 95' E-350 7.3 PSD

 

[Crumm]

Welcome over to the site dieselweasel, glad to have you on board

 

[DaveBen]

Yes, I too would like to welcome you to this site. Good explaination on the alternator charging scheme.

Dave

 

[dieselweasel]

Thanks for the welcome!

I forgot to point out that while SSD and LRC of the regulator account for the behavior that was described, I'm not sure that these features are part of the stock regulators on the 7.3 PSD and shouldn't be considered "normal" behavior. They are found on replacement regulators that aren't an exact electrical match for the OEM part. The stock regulator Motorcraft replacement part #GR-821 doesn't have SSD/LRC as far as I can tell. Parts GR-818 and GR-814 are physically compatible, and do have SSD/LRC.

The only reason I researched this info is that my 95' E-350 showed the exact same behavior, which I found odd, and put my mechanic on a wild-goose chase trying to find the source why the charging didn't kick in right away and when it did, the voltage rose slower than it normally would when the engine was revved.

Even though SSD and LRC are found on some vehicles for the reasons I described, they may not be needed or useful for the 7.3 PSD if they weren't used on the OEM parts.

So I think that mudwhistle and I are seeing the results of alternator replacements that were OEM physical matches, but with incorrect regulators.

I'd be interested to see if others with the stock 3G alternators could confirm that this charging behavior is different than they experience. I'm also seeking information on replacing my alternator with a 200+Amp model (E-350 w/o Ambulance package).

 

[JOAT]

The delay shown in the charging is NOT directly due to the glow plug circuit. It is due to two features of the regulator control circuit, Soft Start Delay (SSD) and Load Response Control (LRC)....snip

dieselweasel - 95' E-350 7.3 PSD

DUDE!!!!!
Thanks

I have long suspected something of that nature, but several posts asking about that "elsewhere" got me zero responses. Welcome and thanks for the info.

 

[whatabudro]

Yes, WELCOME, feed me more info anytime. Bryan