REFLECTOR: egt and cht problems

Ron Brown romott at adelphia.net
Sun May 1 15:38:57 CDT 2005


Hi Dean,

I agree with the JPI folks.  Sounds like a poor ground somewhere.  You can loosen all of the ground connections, clean them and then put them back on. Make sure there is no paint (like engine block gray) that could be compromising good grounds. You could also check the resistances with a good Digital Voltmeter that can read tenths of an ohm. 

I'm surprised that the starter hasn't melted something down.  Often, if there is a poor engine case ground, it will fry instruments that provide the ground path for the very high amps drawn by the starter. But since this hasn't happened, I would look at instrument grounds.  Since the alternator current is proportional to the instrument problem, look at those grounding paths too.

Let us know what you find.

Ronnie

 
  ----- Original Message ----- 
  From: dean fitzbag 
  To: reflector 
  Sent: Sunday, May 01, 2005 3:11 PM
  Subject: REFLECTOR: egt and cht problems


  I have JPI slim line instruments.  They are a egt, cht, outside air, oil pressure, oil temp, tach, ameter-voltmeter, and fuel pressure.  All are connected to my master panel for the plus side.  All except the egt and cht are grounded to the master panel ground.  The egt and cht are grounded directly to the engine.  All is fine on the ground and in the air provided that no large current is flowing out of the alternator.  If I turn on the gear pump, nav lights, strobe lights, landing lights, electric fuel pump or if the battery needs recharging, then the temperature read outs of the egt and cht will read low.  The more current, the lower the reading.  There is no problem on the ground since my engine isn't running fast enough to drive the alternator output high enough.

  The JPI folks insist that I must have the ground on these two instruments somewhere other than the engine.  I have a direct wire connection.  The voltmeter reads 13 to 14 volts.  The ameter reads 2 to 3 amp on the ground, normal 8-9 in the air without the additional load of the above devices, and up to 15 and above with them.

  I have the factory wiring system.  The engine ground and panel ground meet at the battery.

  The cht will drop about 50 degrees with the nav lights, and another 100 degrees with the landing lights.  The drop seems to be proportional to the extra current.

  Any ideas?


------------------------------------------------------------------------------


  _______________________________________________
  To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector

  Visit the gallery!  www.tvbf.org/gallery
  user:pw = tvbf:jamaicangoose
  Check new archives: www.tvbf.org/pipermail
  Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.tvbf.org/mailman/private/reflector/attachments/20050501/8a69ab5d/attachment.html


More information about the Reflector mailing list