BJ40 24 volt gauges

[WDT Siri]

I will look for a suitable small sized Voltmeter that could be "inserted' to the cluster @ Amp Gauge location.

Thank you veruy much Rudi

 

[orangefj45]

I have this 24V cluster from a 1979 BJ4x if anybody needs it.

Georg @ Valley Hybrids

 

[bj40green]

That is a "hybrid" cluster.
Odo counter is 5 digits which is pre '82
OIL, FUEL and TEMP are '79 and later
Amp gauge is pre '79
So it's a '79, '80 or '81 cluster with a 30-0-30 Ammeter from a '73 till end '78 cluster.

BTW: easy to convert to 12V.

Rudi

 

[acmarc]

I have this 24V cluster from a 1979 BJ4x if anybody needs it.

Georg @ Valley Hybrids
View attachment 865738

GEORGE, hello, do you still have the 24v dash cluster available?
regards
Marc

 

[MMK68]

It's important to understand that a 24V cluster is a 12V cluster with 3 modifications.
1. The voltage for the FUEL and TEMP gauges is lowered from 24V to 12V by a 30 ohm dropper resistor.
2 The OIL gauge is 24V.
3. All light bulbs are 24V.

First: check the value of the dropper resistor. It should be 30 ohms +/- 20%.
If the reading is MUCH more it means it's defective, blocking the current flow.
If it's "OL" (Open Loop) you should not have 24V on the left side.

You can apply 24V to pin 3 (or the right side of the dropper resistor) or you can apply 12V to the left side of the dropper resistor (= left stud FUEL gauge).
May I suggest that you use an in-line fuse for this purpose. I mean you can do some nice welding with a battery.
View attachment 859021
At this point the internal VR (Voltage Regulator) inside the FUEL gauge should start working. This VR is a bi-metal that switches the 12V on and off which results in an average 6 to 7Volts. This voltage appears on the top and right stud of the FUEL gauge. If you use a digital volt meter you'll see rolling numbers. If you use an old school analog meter you'll see a wobbly needle around 6 -7 Volts.
Most people don't know how to handle this and that is why the FSM says "dont test this".
Okay. The top stud is the output for the TEMP gauge and the right stud is the same as pin 4 for the FUEL sender.
Pin 5 is for the TEMP sender. So on pin 4 and 5 there should be that wobbly 6 - 7 Volts.
Pin 2 is for the OIL pressure sender (which has an build in VR BTW) and this pin should show the same voltage as what you applied on pin 3, so 12V or 24V.

Rudi
View attachment 859021

Super helpful. Thank you