Glow plugs not working

[Napalm]

Recently changed my glowplugs, 3 out of 4 were dead however i seriously cracked and broke some parts of the harness doing so, issue was fixed for a couple days, but then rough cold starting came back, figured it was the harness so ordered a new one, however im getting no power through the wires of the harness so no point in wiring the new one to it, fuses ontop of battery are fine, the coil symbol appears for a split second on the dash when the key is turned, can anyone suggest what this could be,
Thanks in advance

[Napalm]

-no power on harness wires
-fuses ok
-relay unchecked as yet to locate

[Napalm]

Issue cured, water has rusted the relay out,

[Napalm]

The issue is again at the Relay. Im getting 8v at the fuse box but the relay is not 'clicking' and thus no power is reaching the glow plugs. HOWEVER i hooked the relay up to a variable transformer and it clicks at 5 volts. It also clicks at 12 volts off a drill battery. WTF! is anyone able to enlighten me