Engine and transmission computer troubles. HELP!

[Mike McMahan]

Can you provide us with a little more info? When and how did this
start? Has any diagnostic work been done where any of the plugs
have been disconnected? Does the repair shop have anyone
experienced with a DDEc 1. Many shops are not equiped with a reader
for the DDEC 1. I have found the biggest problem with this system
to be the grounds. That said I don't believe that a ground would
cause the problem. Have you driven the coach with the retarder
off? If so what happened? Let us know everything you can and I'll
try to help. We have a great Stewart and Stevenson shop in Waco. I
know most of the guys there pretty well and they are familar with
the DDEC 1. If you want to call my cell is 254-913-1176. Mike
McMahan 1989 PT 40 Waco, Texas


--- In WanderlodgeForum@yahoogroups.com, "Leroy Eckert"
wrote:
>
>
>
> I have not experienced problems like you describe. I have learned
from experience, this Forum, reading and discussions with others
that poor grounds can cause havoc. I have also read that DDEC can
do weird things if the voltage is not correct in the unit.
>
> That said, if I had the problems I would first verify that all
major ground straps have integrity. Main battery grounds, engine
and tranny to frame straps etc. I would also check the major ground
connection in the lower load center where most of the relays are
located. Check the connecting plugs at the DDEC for corrosion and
correct power to the unit.
>
> I cannot visualize a sensor that would cause those problems other
than maybe the throttle position sensor and I cannot envision how
that would cause the retarder to act up.
>
> I hope this gives you a starting point and you are successful.
Please let us know what you find.
>
> Strange stuff for sure. I hope others have more info or ideas
than I.
>
> Leroy Eckert
> 1990WB-40"Smoke N Mirrors"
> Niceville, Fl
>
>
>
> ----- Original Message -----
> From: fmc360
> To: WanderlodgeForum@yahoogroups.com
> Sent: Monday, April 23, 2007 7:26 PM
> Subject: [WanderlodgeForum] Engine and transmission computer
troubles. HELP!
>
>
> This is my first attempt to communicate my problems with my
> 1989 PT40, 8v92 with DDEC1 and Allison 748 transmission. After
> many hours with the professionals in diagnosis, it appears to
> be a sensor somewhere....my symptoms are (1) between 35 mph and
> 50 mph with mid-ranch rpm of 1500 to 1600 the transmission
> shifts between 3rd and 4th gear, (2) the retarder tries to
> operate with acceleration, (3) all of the buttons on the shift
> panel are illuminated at once with the selected gear the
brightest
> on the panel. I am thinking that all of these problems are
> connected in some way.....? Has anyone experienced any of these
> problems?
>
> P. S. The coach is now with Stewart & Stevenson....and has been
> for two weeks....I guess if they can't fix it you don't need it!
>
> 88101 PT40
> Carroll & Sandra Wooten
> Madisonville, Texas
>
>
>
>
>
> [Non-text portions of this message have been removed]
>