2 speed fan and control box on 3 speed car - Straight swap?

agw_01 · 18th August 2019, 20:05

Evening all,

I was under the impression that the cooling fan on my ZT diesel could be directly interchanged if the corresponding relay box was fitted at the same time. I've just literally finished swapping the old broken 3 speed fan for a 2 wire, 2 speed fan and 2 speed relay box. I upgraded the resistor at the same time.

The fan I was supplied had the connectors cut off where they plug into the car so I removed these from my old 3 speed fan and soldered to the wiring from the new control box.

I did notice that one of the wires was a different colour, blue on the 2 speed rather than blue/red on the 3.

Once all connected up, I tried to run the fan by turning off ECON mode on the AC but I just seem to get a buzzing from the relay box and nothing from the fan.

Before I go back out there (not tonight!!) and start troubleshooting, could someone please confirm whether directly replacing a 3 speed fan with a 2 speed fan and their matching relay boxes should be a direct plug and play replacement? The pins used on the car's loom are the same and all low/high speed switching is done in the relay box?

Thanks!

18th August 2019, 20:05	#1
agw_01 Regular poster MG ZT Join Date: Jan 2018 Location: UK Posts: 64 Thanks: 4 Thanked 9 Times in 8 Posts	2 speed fan and control box on 3 speed car - Straight swap? Evening all, I was under the impression that the cooling fan on my ZT diesel could be directly interchanged if the corresponding relay box was fitted at the same time. I've just literally finished swapping the old broken 3 speed fan for a 2 wire, 2 speed fan and 2 speed relay box. I upgraded the resistor at the same time. The fan I was supplied had the connectors cut off where they plug into the car so I removed these from my old 3 speed fan and soldered to the wiring from the new control box. I did notice that one of the wires was a different colour, blue on the 2 speed rather than blue/red on the 3. Once all connected up, I tried to run the fan by turning off ECON mode on the AC but I just seem to get a buzzing from the relay box and nothing from the fan. Before I go back out there (not tonight!!) and start troubleshooting, could someone please confirm whether directly replacing a 3 speed fan with a 2 speed fan and their matching relay boxes should be a direct plug and play replacement? The pins used on the car's loom are the same and all low/high speed switching is done in the relay box? Thanks!