thank you for your suggestions.

I don't know how the tach gets its signal and haven't had time to contact Detlev to check. The fires in Northern California have kept me busy.

It has also been suggested that there is a resistor in the instrument cluster that could explain the tach and the temp red flashing light symptoms also experienced.

any thoughts on this?

Mike
--------------------------------------------
On Mon, 9/14/15, SDF ( aka ;jim lahey' - Scott ) <scottdaniel@turbovans.com> wrote:

 Subject: Re: bouncing tach
 To: "Mike Miller" <mwmiller6@ATT.NET>, vanagon@GERRY.VANAGON.COM
 Date: Monday, September 14, 2015, 1:42 PM
 
 
     since it's a TDI,
 
       I would ask what signal is going to the tach ..
 
       is it alternator-sourced or is it directly from the
 ECU ?
 
       if the former ...one might look there some. 
 
       
 
       "tdi conversion " 
 
        is a very good list for this sort of thing. 
 
     
 
     On 9/13/2015 3:27 PM,
 Mike Miller
       wrote:
 
     
     
       Yeah, I forgot. with a van always start with the
 grounds. Even for a flat tire.
 
 
 --------------------------------------------
 On Sat, 9/12/15, Dennis Haynes <d23haynes57@hotmail.com>
 wrote:
 
  Subject: RE: bouncing tach
  To: "'Mike Miller'" <mwmiller6@ATT.NET>,
 vanagon@GERRY.VANAGON.COM
  Date: Saturday, September 12, 2015, 6:05 AM
  
  You either have a bad connection
  somewhere causing false pulses, interference from
 something,
  or the tach itself. I would start by looking for wiring
  issues starting at the chassis, (ground) connections. 
  
  Dennis
  
  
  -----Original Message-----
  From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com]
  On Behalf Of Mike Miller
  Sent: Friday, September 11, 2015 8:09 PM
  To: vanagon@GERRY.VANAGON.COM
  Subject: bouncing tach
  
  Vanners,
  
  For the second time the tach in my 87 syncro westfakia
  converted to TDI went crazy for a while. Bounced up and
 down
  and all over then after a few minutes went back to regular.
  It a diesel dash pod with a diesel tach.
  
  It was very hot yesterday but the first time it happened it
  wasn't hot so….?
  
  I have a tech tool hooked up  and it shows a steady
  tach reading. but it's kind of disconcerting.watching
 the
  dash board tach go nuts.
  
  Any ideas on what goes wrong and how to fix it.
  
  Mike