Harness plug hot spot is switching valve port.<br/>Left side middle port.

 

Oh, okay. The check valves replaced the return valves, this so return fuel can go into the tanks but not the other way 'round, correct?

For a minute I was thinking you had check valves on the supply side.

Thanks and cheers
DD

 

I often defend Lucas wiring because I find that the complaints are often overblown but, IMO, this is an example where the criticism is called for. It's a poor design. There's really nothing to securely hold the connector firmly onto the switch so they often become a bit loose. Loose fit = high resistance = high heat = melted

Cheers
DD

 

Yes, you are right. I cleaned and squeezed the blades tighter and wrapped a plastic tie band clamp around the entire switch.

 

Or trash (from tank) in the changeover valve, =high current from stressed valve =melted at marginal connection.