Cultus 2011 AC making noise as if a belt/pulley is stuck

muflah (Muflah) 2024-10-21 23:08:27 +0500 #1

When I turn on the AC, AC fan doesn't start and I'm assuming that the compressor is making weird noise as if the pulley is stuck and would cut off frequently (I can hear the magnetic clutch). After sometime when the fan starts blowing air the noise disappears. I'm assuming that the fan should start when I turn the AC on and keep on until the compressor is on. I'm also noticing that when it's hot (in the afternoon) the AC stops working. So what could be the issue? Faulty wiring or something related to the ECU? Or a faulty fan motor?

muflah (Muflah) 2024-10-22 02:31:41 +0500 #2

Found the problem. The same wire is turning on the compressor and AC fan. The fan motor is most likely faulty.

Xulfiqar (Xulfiqar) 2024-10-22 02:59:02 +0500 #3

Is the diode missing?

muflah (Muflah) 2024-10-22 19:37:18 +0500 #4

What diode? The fan wire is shorted to compressor wire without a relay or anything. Where's the diode supposed to be?

Xulfiqar (Xulfiqar) 2024-10-22 19:45:04 +0500 #5

There should be a diode in the wiring that prevents the compressor starting when the radiator fan alone starts (e.g. no ac command from driver control panel but engine fan is switched on due to temperature).

Its usually right by the compressor relay and may also look like a relay but has diode symbol on it.

muflah (Muflah) 2024-10-22 21:14:20 +0500 #6

Oh, I was talking about the AC fan. I can check the logic, so what's supposed to happen when I start the car on cold engine and start the AC? Both AC compressor and AC fan should turn on? And when the radiator fan kicks in the AC company and AC fan should be off? That's not what I have observed tho. In my case when I turn on the AC both the AC fan and AC compressor start irrelevant to the radiator fan and both the compressor and AC fan are turned off when evaporator reaches a certain temperature.

Xulfiqar (Xulfiqar) 2024-10-22 22:00:53 +0500 #7

When you run the ac regardless of temperature of engine, the compressor should kick in along with cooling fan(s) - this act keeps the coolant temperature lower than the actual fan kick in temperature.

The fan will cycle with the compressor clutch, however if you are driving with ac off, the engine fan will kick in when coolant gets hot enough.

The way its intercepted is by use of a diode, it prevents the compressor relay being started by the fan relay. The diode will be a two pack type, one diode does the job as mentioned, the other acts a flyback diode.

In some cars you may find a single diode, those cars had the flyback diode at the compressor connector.

muflah (Muflah) 2024-10-24 00:41:30 +0500 #8

I think Cultus didn't come with this setup or someone removed the diodes from mine. Do you think it'd be better to use a 5 pin relay to bypass radiator fan relay and add extra (fly back diodes)? A bit hesitant in energizing radiator fan with the existing AC wiring, it's been cut and reconnected by local shops.

By the way I have been driving it without diodes and haven't faced any overheating issues till now.