BX Coolng Fan Operation

[Roscoe]

Hi All. I was working on my TZD and 16V today and figured I had something wrong with the cooling fans on both of them, but I'm not sure after checking my parts car as well. What I have done is: remove plug from temp sensor switch in radiator and short from the earth to the low speed terminal - with ignition switch on both fans run in low speed - on all cars (with A/C turned off). When I short between earth and the high speed terminal, only one fan runs on high speed, the other stops - this happens on all three cars. When I do the same with the A/C turned on, the low speed operation is the same, but when I short the high speed terminal to earth, BOTH fans run in high speed - only on the 16Vs as the TZD doesn't have A/C. According to some old posts and a Peugeot cooling document, as well as the wiring diagram, I would have expected BOTH fans to run in high speed regardless of whether the A/C was on. When only the A/C is switched on, both fans on the 16V run in low speed.
So is the way my fans run correct, or is there something wrong? I can't figure out the point of only having one fan run on high speed if the engine temp is excessive - would have thought both should run. But since it is the same on all three BXs, I'm wondering if this is correct.
Anyone else tried this and have the same results?

[Clogzz]

Not sure about the BX, but if it’s the same as the Peugeot 306 diagram, then if the ‘change-over relay’ is not energised or conducting, only one fan will spin at the high speed.
At the low speed, only the ‘left fan relay’ is energised, while at the high speed all 3 have to be energised for both fans to spin.
Shorting the high speed terminal to earth doesn’t activate all 3 relays.