'79 FJ40 gauges not working (1 Viewer)

[sloanstavern]

Time to breathe life back into this thread, I’m on a similar path. 82 FJ 45, brand new OEM instrument cluster and a painless universal wiring harness on a fresh rebuild. I did not wire a three prong Ameter fitting

Fuel oil and temperature gauges were working fine then stopped. Took everything apart and confirmed all the wiring was correct, checked for continuity across the cluster board and no resistance on the power side for those three gauges, when I check for voltage across the barrel connector solid 12 V for each of the three gauges. I even did the 3 W lightbulb gauge check and all three passed with flying colors.

However when I connect the barrel to the cluster the voltage across the fuel age posts jumps all over the board a true random number generator.

Any thoughts would be greatly appreciated

 

[JVZii]

Curious when you hot wire the oil pressure gauge does the needle move on the gauge? It should jump up right away.

The fuel gauge has a mini voltage regulator in it which may be why the voltage jumps around.

A word of caution if you bridge 12v across the 2 bottom posts on the fuel gauge without grounding out the case, it will fry the fuel gauge pretty quick.

The cluster bible is below. I think I linked to the page that explains all the gauges. Hope it helps.

Post in thread 'Clusters, Gauges, Speedo & Odo meters' Clusters, Gauges, Speedo & Odo meters - https://forum.ih8mud.com/threads/clusters-gauges-speedo-odo-meters.544543/post-7248496

 

[sloanstavern]

Curious when you hot wire the oil pressure gauge does the needle move on the gauge? It should jump up right away.

The fuel gauge has a mini voltage regulator in it which may be why the voltage jumps around.

A word of caution if you bridge 12v across the 2 bottom posts on the fuel gauge without grounding out the case, it will fry the fuel gauge pretty quick.

The cluster bible is below. I think I linked to the page that explains all the gauges. Hope it helps.

Post in thread 'Clusters, Gauges, Speedo & Odo meters' Clusters, Gauges, Speedo & Odo meters - https://forum.ih8mud.com/threads/clusters-gauges-speedo-odo-meters.544543/post-7248496

Thanks, when Iused the 3 W lightbulb the gauge moved gently across the range. I have since discovered the root cause of my problems. The oil pressure gauge had a bad connection at the barrel fitting, I cleaned it up and it’s working fine. Regarding the fuel gauge, it was a bad ground near the sending unit, for the life of me I do not know why I wait so long to check all the grounds