Faulty fuel gauge and rev counter

[PasQuYto]

Hello, i have recently bought myself a 1990 T3 1.6TD with a faulty rev counter and fuel gauge.
I am wondering what are the first things to check, i would especially like to fix the fuel gauge.
Thanks

[Aidan]

first thing to check is the security of the 14 pin connector to the binnacle circuit board then the condition of the edge connector tracks on the board and getting familiar with the whole unit and condition thereof - all the info is in Bentley for testing it in logical flow diagrams
then it is generally a matter of continuity testing to work out if it is wiring issue and if so where the fault is or dash mule(s) not working

unfortunately on a 2wd the earth for the fuel tank is above the tank on the chassis rail and is prone to corrosion, without the earth the sender won't work

[PasQuYto]

How can i access the Bentley manual?
Thanks

[chrisevans]

Bentley is copyrighted but I believe it is on the net somewhere - best to buy a copy as it invaluable


Sent from my iPhone using Tapatalk

[Oldiebut goodie]

Join the club then:

viewtopic.php?t=110469

[PasQuYto]

I have tested continuity on the board, it seems fine.
I am not getting any voltage on the 7th pin of the 14 pin connector. Does this mean the sender is broken, which means i have to drop the tank as it is not a syncro?

[Aidan]

with plug disconnected you measure resistance to earth on the connector, if open circuit then either sender has failed, or the earth connection above the tank or the wiring between the sender and the body earth is damaged, usually due to corrosion issue - high resistance will make fuel gauge read low/empty, open circuit is effectively infinite resistance

resistance should be in the 35-270 ohms range iagtu full-empty

 

[syncroandy]

The OP mentioned a couple of things on the dashpanel that aren't working, we don't know what else may not be working.

I suppose its safe to assume the speedo IS working, but of course that's fully mechanical in operation.

Possibly the dashpanel has no power in at all and is completely non-functional aside from the speedo ?

Probably worth clarifying there's battery power on T14/5, earth on T14/2, and ignition on T14/8 ?

The dashpanel BAT+ input shares fuse S3 (15A) with the radio and cigarette lighter so is rather prone to getting blown.

Earth is via the dash wiring harness to the LH A-pillar earth crown, which are a well-known weak point.

Ignition is unfused, wired directly via the dash wiring harness to the ignition switch.

If there IS good power and earth, at ignition-on , the alt charge, oil pressure, and glowplug lights should all come on.
 

[PasQuYto]

Yes everything else works on the instrument cluster except the rev counter and fuel gauge.
The earth crown behind the fuses looks fine


I found a red/brown wire behind glovebox in the air, any idea for what this is?

[Oldiebut goodie]

The earth crowns do not look fine - not the worst but there is corrosion to be seen. Have you removed all connections and checked them as it doesn't look like they have been moved to my old eyes.