1998 dynasty replaced the duvac with a delco 28 is tack reading high

[Mike Farquharson]

Hi did the conversion removed the ssi. batery maintainer and the big boy solenoid replaced with ml-acr started coach had good charging problemmatic tack that usually reads just over 500 rpm and unsteady was reading 1400 rpm but steady went to shut down  and motor would not shut off.  Removed the sense wire from ignition term and motor shut down. If I want to use the sence wire do I need to put a diode inline and what diode would I need . Can the tach be calibrated to the new alternator.

 

THANKS MIKE

[Tom Cherry]

https://www.monacoers.org/search/?q=duvac tachometer&quick=1

DUVAC TACHOMETER key words   Searched TOPICS

https://www.monacoers.org/search/?q=alternator tachometer&quick=1&type=forums_topic

ALTERNATOR TACHOMETER key words. Searched TOPICS

Hope this helps.  In the future, it is a mandatory or guidelines requirement that PRIOR to posting you research your issue (presumably GOOGLE) and do a Search here.

I didn't bother to do the Googling but suggest you do.

Hope these are of value, but please comply with the guideliness.

Sounds like you are on the right track with the ML-ACR and if you are getting proper charging with the new alternator...then reading these and/or contacting, via PM, some of the more knowledgeable posters will help.

Once you have got a better understanding of the issue or fixed it, please followup with the solution.

Thanks,

[Benjamin]

You have some different things going on.  The tach should not need to be recalibrated, is the tach wire hooked to the R terminal on the delco?  the tach would have been to one of the three identical unlabeled inner terminals on a Leece Neville, right?  If it is reading 1400, that sounds like three times actual speed, so reading AC frequency from all three phases, not just one, if that's possible. 

If you have a genuine delco 28SI with a solenoid isolator (not a diode isolator), then you don't need to use the remote sense or ignition terminals on the delco.  An "alt fail" relay, or battery warning light, will not work without the ignition wire hooked up.  A diode, or possibly a resistor will allow the warning light to work and the engine to shut off. The remote sense and ignition are different terminals and wires.  If you have an aftermarket copy of a delco, all bets are off.

[MHRookie]

Mike,

search the net a bit more.  This site & IRV2 site both have info to share.  I did like you replacing my original charge equipment then the 28si alternator.  I don’t have the cheat sheet I made from the shares but of the 3 wires…. The ignition wire can be left unhooked OR a diode can be installed (I chose the diode).  As I recall, that corrected the engine shut down issue from ignition.  NEXT, you may have the other 2 wires crossed if tach is reading 1400.  I used my coach print to verify which wire got hooked up to the 28si install directions.  

[Mike Farquharson]

Update I have spent 2 weeks resurching the alternator up grade spent 7 hrs yesterday alone on this site and  Irv2. foretravel and other webb searches before I posted .  It ia a delco 28si and removed alternator this morning double checked the wiring. Delco terminal  S wire goes to 12 volt buss bar, terminal I goes to TS2 ignition, terminal S goes to relay ALT FAIL .    IF all wiring hooked up engine wont shut down. removed wire going to terminal S and still wont shut off, removed wire going to terminal terminal I and it shut down. With wires removed from terminals S and I will start, run ,and charge at 14.1 volts but tach still reads 1300-1400 rpm. Any ideas

 

Thanks for your patience

 

[Benjamin]

Terminal S (remote sense) is not needed for the alternator to produce 14v.  It is only needed with a diode isolator, or to compensate for other voltage drop. Terminal S connected correctly will not interfere with shutting off the engine.

Terminal I is also not needed to produce 14V, but if hooked to ign will need a diode, or possibly resistor to allow engine to shut off, that is the biggest difference between a delco and Leece Neville.

Tachometer wire should go to terminal R as far as I can tell.  You mention two connections to terminal S but nothing to terminal R, please confirm.  if terminal R will not work the tach correctly, then you can take the alternator apart and add a tap directly to one winding for the tach signal, I don't think that's needed with the R terminal though. 

Edited July 23 by Benjamin

[MHRookie]

From my wiring install the three wires on back of Leece Neville.

leece Neville hooked to 28si

yellow (ignition) goes to “I”

Red 12v -I hooked to “S”

gray “alt fail” goes to “R”

these 3 wires were in a protected shield and connect to a plug about 3ft away from alt.

i installed the one way diode on the “ignition” wire.  
all works and functions correctly.

lets do one simple test… unhook all 3 small wires from the back of 28si.  Only use 12v+ &-.  See what tach does then.  RPM signal may not come from alternator but rather the ECM. 

Edited July 23 by MHRookie

[Mike Farquharson]

Thank You , will try to source the diode and will try again.

That is the way i am wired .

 

Thanks Mike

[MHRookie]

Mike,

     Here is the diode I used from Painless performance…

https://painlessperformance.com/product/alternator-backfeed-diode-kit-part-no-30720/

[jimc99999]

On my 97 Windsor I only hooked up the tach wire, and the alt fail light works properly.  This alternator is a Pasco, I think on Delco alternators the W terminal would be labeled R.

The 97 Windsor has the C8.3 mechanical Cummins motor so there's no ECM. I'm not sure when Monaco switched to the newer motors with ECMs but I think that was in the 98-99 timeframe.

[Mike Farquharson]

Hi guys diode came today installed and motor shuts off tach is working , if i remove the diode tack reads double, I have no idea why. Still waiting for delco support to call back.  The diode I used was a 60 volt 5 amp from amazon.

 

Thanks two all for your help

Mike

[MHRookie]

Glad it all worked out.