Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > Porsche 928 Technical Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Registered User
 
Join Date: Feb 2013
Posts: 70
84 928 Tachometer Non-functional

Hi to All!
After years of operating correctly, the tach suddenly stopped working. Checked all fuses and all appeared fine. I'm hoping the instrument panel doesn't have to be removed. Looking at the schematic in the factory repair manual is difficult making heads or tails where it leads from the distributor. Any clues of what might cause the issue and clarification on the tach wiring would be appreciated.

Last edited by GabrielS; 07-16-2019 at 07:43 PM..
Old 07-16-2019, 10:27 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Registered User
 
JK McDonald's Avatar
 
Join Date: Oct 2003
Location: Texas
Posts: 988
Garage
Edge Connector -

Hey Gab - On "Miss Purdy" I've found that most gauge issues simply needed the edge connectors and/or the ribbon circuitry cleaned a bit. There are a couple of good Rennlist write-ups on "How To" clean the connector plugs/printed circuit traces for a 1984 instrument panel. Here's one -

https://rennlist.com/forums/928-forum/706384-instrument-cluster-and-central-warning-unit-with-color-wires.html

The tachometer signal originates from the Ignition Control Unit (passengers inner fender well - near radiator hose). Then to the sideways center black edge connector in the photo. Next it heads to the 3 brass terminal nuts (B+/Grd/Tach Input Signal - shown in the center of instrument panel). You might try very gently reaching up behind the instrument panel with a long screwdriver and "SLIGHTLY" moving the black connector plug. Make sure to disconnect the battery for safety and be careful not to pull the edge connector completely off. If you are a lucky duck, re-seating the connector plug will be enough to reestablish your tach signal. If this doesn't help - the instrument pod may have to come out to clean/tighten the 3 brass nuts a bit.

Good Luck- Michael
__________________
1984 928S - "Miss Purdy"
1987 911SC - "Frau Helga"
1986 930 - "Well Hung"
1975 911 Targa "Blue"

Last edited by JK McDonald; 07-17-2019 at 05:05 PM..
Old 07-17-2019, 04:58 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered User
 
Join Date: Feb 2013
Posts: 70
Hi Michael!
Thank you so much for your reply and the picture, they will aid me greatly. Will attempt after recovering from a mean sinus infection which greatly interfered with cognition of anything, especially the reading of a schematic.
Cheers!
Gabriel
Old 07-17-2019, 08:57 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Registered User
 
JK McDonald's Avatar
 
Join Date: Oct 2003
Location: Texas
Posts: 988
Garage
Wiring Schematic -

Hey Gab - In 1984 Porsche changed the 928 wiring schematic format to a confusing hodgepodge of seemingly unrelated and almost untrackable reference points. The previous year schematic format to 1983 are clearly laid out, concise, logical and each circuit is very easy to follow from page to page. The great part is that the 1983 schematics can be used for our 1984 cars...

If you don't have a copy of the "928 Maintenance Manuals" on CD's get a copy. Then print out a few sets of the 1983 wiring schematics in a large easy to read 14" x 8" format. (Keep one set back as an unused reference copy and at least one as a working copy). My working copy has all my notes, comments, Pelican Parts member's discussion info all over them and are about worn out.

Good Luck - Michael
__________________
1984 928S - "Miss Purdy"
1987 911SC - "Frau Helga"
1986 930 - "Well Hung"
1975 911 Targa "Blue"

Last edited by JK McDonald; 07-18-2019 at 09:42 AM..
Old 07-18-2019, 09:22 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Registered User
 
Join Date: Feb 2013
Posts: 70
Great info to know Michael, I'll look into it. Thanks Again!
Gabriel
Old 07-18-2019, 08:06 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 03:35 PM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.