As said the wiring is a chronic weak point, along with the fuel pump wiring!

Don't mess around with the standard wiring as it was substandard when new, leave alone now!

Either make your own loom or buy one premade and then rewire straight from the battery.

There is no timer delay, it's merely a thermoswitch that closes at a predetermined temperarture and opens below this temperature, this is what trips the relay which then powers the fans.

The OE switch again is bad, thus "Uprated" switches being avaliable which have a better span than the original.

Martin