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Acura MDX Sport 2007: radiator fan, condenser fan and A/C compressor clutch not working

2257 Views 0 Replies 1 Participant Last post by  PatDS
Hello all,

Thank you for reading my first post here!
Looking to pinpoint the problem i have with my MDX 3.7L Sport package (Yes, the one with the electronic shock suspension).

Here is the problem:
- Radiator fan, condenser fan and A/C compressor clutch do not start/engage (low speed as well as high speed).

No code or light in the dashboard.

Car does not overheat (probably because I am not stuck in traffic very often, don’t drive long period of time in the city and the coolant radiator is new and pretty big on that car imho) but fuel consumption is on the high side. Engine runs fairly smoothly also.

Here is what I have done/tested so far:
- Fuses: tested and checked all of them (under hood as well as under dash) = all good.
- Relays: Radiator fan relay, A/C condenser fan relay, A/C compressor clutch relay:
- Tested the relays one by one and even swapped them with other ones.
- Bought the new A/C compressor clutch relay (upgraded part 39794-SDA-A05) and replaced the old one = all good
- Engine coolant sensors (ETC1 and ETC2) read 2410 ohms and 2340 ohms respectively (when cold):

Result: Not working at this point.

I figured I needed to focus on the radiator fan so it would be easier to start with (knowing the A/C compressor clutch won’t engage if coolant pressure is too low or even if the condenser fan does not start).

Removed the radiator fan relay and, with help of a jumper wire, was able to start the radiator fan connecting no1 and no2 socket terminal in the relay box (warmed up the car and left key in acc position). Tried the same thing (jumper wire) with the condenser fan and the A/C compressor clutch and the clutch engaged and the A/C condenser fan started. Phew!

Also, I was able to get the fan to start at low and high speed with the engine on and after off so the fan control relay looks good also...

My assumption is that the circuit after the relays, everything looks ok.

Next thing I tested if I had electric current at the fan relay socket coming from the Powertrain Control Module (PCM). So I tested the voltage between socket terminal no4 (Pos) and socket terminal no3 (Neg) and got a very low reading, a bit over 2 volts, not enough to engage the relay. Just out of curiosity, I tested the voltage between socket terminal no4 (Pos) and a ground point on the vehicle and got over 12 volts.

I believe I might have a bad ground connection somewhere so I have no continuity between the socket terminal no3 (Neg) and a ground point on the vehicle (vehicle hot).
Is there somewhere I should look or any other test I should do?

Thank you!

I have included 2 images (Relay and control unit locations, Fan control circuit diagram).


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