Function test tri-gauge 101.23 spider

[Za-gato]

Hello,
This question might have been asked many times. Tried to use the searching tool unsuccessful.

Short background:
All instruments are served and repaired. The car is the 101.23 Giulia Spider 1964.

I don't get any response from the tri-gauge fuel level indicator when connected to the cabling.
I don't trust or expect the fuel tank sender unit to work correctly why I'm asking if alternative test can be arranged outside the car.

Another question is what value to be expected on the multimeter instrument measuring the fuel sender unit. Between "ground" <--> "fuel reserve" and between "ground" <--> "fuel level".

[GTD]

Joakim
No response at all indicates: a) No wire connection between fuel sender unit to gauge. b) No ground connection at gauge or at fuel sender unit. c) Malfunctioning fuel sender unit.
Failure of the gauge itself occurs very rarely.
I understand that your gauges have been restored so this should not be a problem.

An Ohm meter should display a 8 to 10 Ohm reading when fuel sender is in empty position; between ground (-) and T - fuel level terminal - red wire.
It should read 80 to 100 Ohms when fuel sender is in the full position.

I prefer to connect a 12 Volt supply to the terminals and monitor the voltage output of the sending unit. This is because the "wiper" type connection inside the sending unit can give erratic readings when tested with only an Ohm meter.

A link to a previous post can be found HERE

[Za-gato]

Thank you GTD for your information.

The problem is solved.
Here is the verdict.
Fuel tank level sender was grounded as the isolation was more or less gone. After repaired by fibre washes the coil was again showing ohms and seems to be alive and working.

The bad guy was the TRI-GAUGE instrument and especially the fuel tank level instrument. The coil thread was broken and lost connection to the terminal. After some discussion within local Alfistas its more or less these errors to expect when instruments are not working. If no ohms to be found between the terminals then it might be a broken thread.

Yes, All instruments was shipped to PA Speedometer Inc for overhaul and test. If needed also to be repaired.
Honestly, I had no worries that the TRI-GAUGE instrument was broken. After information from AlfaBear I got one tips to search for information and got this LINK: http://www.alfabb.com/bb/forums/720165-post8.html

Sadly my fuel level instrument failed the test. “Gone fishing”. Now I needed to make a decision whether to contact PAS and ask what they did and how they did it or just replace the instrument coil myself with a working one from spare instruments.
I have no time to contact PAS why I just open the instrument and replaced the coil and indicator needle. After repair the test with the multimeter/test instrument shown fair values and pass my test.

[GTD]

Joakim
I am glad you resolved your problem.
Your excellent diagram should help others ... but I am puzzled by your inclusion of a Ohm meter reading between #1 and #4
#1 is POWER from fuse #2; #4 is the Tri-Gauge housing (Ground/earth) - the reading between these points must be infinity or there would be a short circuit.

And the POWER (12V to speedo) is connected to the body of the dynamo light (mounted in the Speedometer Gauge).

[Za-gato]

Quote:

Originally Posted by GTD Joakim I am glad you resolved your problem. Your excellent diagram should help others ... but I am puzzled by your inclusion of a Ohm meter reading between #1 and #4 #1 is POWER from fuse #2; #4 is the Tri-Gauge housing (Ground/earth) - the reading between these points must be infinity or there would be a short circuit. And the POWER (12V to speedo) is connected to the body of the dynamo light (mounted in the Speedometer Gauge).

[GTD]

Joakim et All
Understand that the info in the LINK referred to as Oil and water temperature gauges is not directly applicable to 101 series gauges.
The "cold force" and "hot force" electromagnets are not externally adjustable in a 101 series Veglia Tri-gauge.

In order to take Ohm meter readings of the 101 series gauges, using the diagram posted by Za-gato, one must first remove the leads from the clamp on the Fuel Reserve Light housing which connects to numbers 8,7,6. Wires to numbers 2,3,5 must be removed. This ensures that readings will reflect only the resistance of each individual coil or winding.

Ohm reading (may vary by 5-10%) case/ground to winding
4-2 ... 212
4-8 ... 338
4-7 ... 245
4-3 ... 132
4-6 ... 302
4-5 ... 250

Ohm readings across both windings
2-8 ... 125
7-3 ... 114
5-6 ... 52

There should be no continuity between #1 and #4 (case/ground).

[Za-gato]

Excellent, Now its complete.

Thank you.
Br
Joakim