Ford 2600 Instrument Cluster Voltage Anomaly

Yoe777

New User
Hi, I am in the middle of a minor restore of my Ford 2600 Diesel. It starts and runs ok but I am having some anomalies on the electrical side of things with the instrument cluster. I purchased a new instrument cluster but after connecting the terminals I am not getting the various feedbacks that I was hoping for. The harness is in good shape considering the age but I did find a few Voltage issues when troubleshooting. The first issue I found when attaching direct to battery on positive side and negative to the Black lead on the harness by the instrument cluster the voltage was 0 with key off but when turned on it was -10.9v when connected to the instrument cluster and -12.38v when not connected.

Also, one of the idiot lights (assuming the oil pressure warning light because the other is testing normal voltage with the ignition on) shows 12v on the positive side AND negative side when turned on. This to me seems like a short somewhere.

One important note is my alternator has been removed because I am waiting on replacement I don’t know if this would have any effect on the voltage output. Also… these tests where without the tractor running. Could a bad Voltage rectifier cause these issues? Examining the harness I don’t see any rodent damage and it is mostly still covered with the factory black tape.

A final note is that I tried looking at some electrical diagrams that all seem to show 6 pin wiring harnesses. Mine has 8+1. I have attached some pictures for reference and maybe someone could break down my serial numbers as well please. Thanks in advance for any information.


SN.jpg
harn.jpg
 
Last edited:
You have a 2600 diesel with trans pto and 6x2 transmission
Tractor was built May 19, 1976 on day shift
Your tractor being built before September 76 should have a oil bath air cleaner and a wiring harness with 8+1 connector plugs
Models built after September 76 have paper air filter and 6+4 wiring connectors necessary for the air filter restriction light

The voltage stabilizer on many new instrument clusters is nothing more than a jumper wire that doesn’t work well, I’d swap on the voltage stabilizer from the old cluster and see how that works
 
Does someone have a 8+1 electrical schematic? I don't have an issue with my instrument cluster... the issue is with the Black negative coming in from harness.
 
Does someone have a 8+1 electrical schematic? I don't have an issue with my instrument cluster... the issue is with the Black negative coming in from harness.
it got its ground by pluging into the vr... one of those leads went to ground... so.. if you unplug your voltage regulator, you loose your ground... and you need to correct that.
 

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