by DonaldNZ » Mon Feb 18, 2019 9:34 am
while interior fan on, engine running at idle, hp/lp [high pressure / low pressure] is bypassed only long enough to determine pump runs, like 2 seconds max at idle, This will tell you if the pump control system is working.
I've had them where its been open to atmosphere for years and the drier maxed out and pump locked up, and you see the belt load up as the clutch slips.
off road use the leak could be anywhere.
If the pump doesn't run when hp/lp bypassed, I'll be more useful help if you please provide the correct as possible heating and cooling wiring diagram. I look for in rough order of preference; only published by car maker, year, manufacturing plant, country of manufacture wiring diagram. I have found haynes and clymer to be a wag [wild as guess] at times or the US & UK 'assembled' cars use different colours and systems.