HOW TO TEST RADIATOR FAN SPEEDS FROM TRINARY SWITCH (DIESEL CDT/i, 1.8 & KV6 Variants

[Jules]

After several requests from members, thought I'd put it here for reference.
This is a DIY test with No T4 TESTBOOK required !!
The old 4 wire motors have quite a short life and fail between 60 - 80k miles.

Testing LOW SPEED FAN
This test is straight forward and is done with one press of a button!

Set the Aircon to the DEMIST function (this overrides the outside temp even down to -30 Deg C and puts the Ventilation fan on full; this can be reduced manually so you can hear what's going on up front)
Don't confuse the Ventilation/cabin fan with the Cooling fan.
Ventilation fan is behind dash.............cooling fan is behind front bumper!

The cooling fan will operate even if there is no gas in the system, or with the Trinary disconnected, only difference will be the compressor solenoid won't be energised. (via small Relay No7 engine fuse box)
The fan should will come on SLOW speed for 2 speed fans & LOW speed for 3 speed motors (diesel variants)

Then with the Yellow/Grey & black wires shorted the HIGH speed will kick in.

Tests for next speed up from LOW

ie:
3 speed Motors
Tests for Fail Safe MEDUIM SPEED FAN function (compressor protection and for the 106°C and 111°C engine temp range)
Or
Later 2 speed motors.
Tests for Fail Safe HIGH speed (used for extra cooling for compressor & fail safe 112 - 119 Deg for engine)

Also proves whether there is insufficient gas in the Aircon circuit if the fan comes on during the test.

Tools required: Paper clip, or bit of wire or small resistor or even a small 12v bulb!

1.8 & KV6 tests are very similar (wire colours differ but plug pins are the same) but engine has to be running on Petrol versions.
V8 tests differ from this & will follow shortly (wire colours differ and test results

Location of Trinary switch (ALL Engine Variants).
Driver's side bulkhead on small bore HP (high pressure) Aircon pipework.


Wires to short to test HIGH SPEED FAN
Yellow/Grey to Black or two wires opposite eachother furthest apart.


Use a paper clip with flattened ends or a resistor lower than 100 OHMS. After a slight delay the Fan Speed should increase.
(above test with ignition on, engine does not need to be running)





Testing the Aircon A/C compressor solenoid Engine running
The other test you can do if the compressor doesn't seem to be kicking in is is to short the 2 Red/Black wires on the same Trinary plug. (this may prove whether there's any gas in the system or not)

If the compressor now runs, the likely hood is you need to get an A/C specialist to do a leak test & then a re-gas.

Set the Aircon to the demist function (this overides the outside temp) or set the temps to LO Or make sure the inside temp is set 12 Deg C lower than the outside temp.

Fault finding guide for no fan operation

For no Low or High speed check the following.

Check 80amp fuse no 4 in engine compartment.(very rare to fail)

Check the large and small relays in the fan control box (carefully lever 10 clips on the lid to inspect)
Wire breaks have been known between the 2 multi-plugs (behind LH wheel arch liner) and the control box.

Check fan earth CO551 (ring terminal between battery box and inner wing secured by 8mm bolt or measure with meter whether the thick black wires from the control box are in fact earthed)
Check continuity of all wires coming into and leaving the fan control box. Wire breaks and joint breaks can happen in the thick or thin cables. Look for tell tale signs of green copper oxide along the cables to the multi-plugs.

Water ingress may have corroded the copper strands.
If all in order there may be a break in signal lines from ECU to fan control box or on extremely rare occasions the ECU itself could be faulty


Diesel owners:

Control box DIY testing (No T4 required)

To check your fan control box is functioning correctly.

Select demist (ignition ON but engine OFF for diesels)

Get someone to listen at the front grill while you press ECON button every couple of seconds.
The low speed fan relay should be heard clicking.

If it clicks but no fan operation, the motor will have worn out (or see list above)

Within the fan control box lies a small PCB which is a tight push fit on top of the relays. Petrol versions do NOT have this therefore the control boxes are not interchangeable.
The relay PCB receives PWM (pulse width modulated signal from ECU)
The square wave varies the Mark space ratio for the different speeds which then gets converted to DC to switch the appropriate relay coil.
On rare occasions the PCB itself can go faulty.
Sometimes the delicate components don't survive the stresses put on them during the gentle levering process to remove it from the relays.

If all in order and still no fan operation, 99% of the time a replacement kit will solve the fault.
Failing all the above the fault maybe a faulty engine ECU if it’s been flooded by blocked plenum drains.
Email any technical queries to [email protected]




Do not attempt to get Air conditioning functioning until you are satisfied all the cooling fan speeds are working. Compressor damage will occur if insufficient cooling for the condensor & more importantly the engine!


Usual disclaimer applies: You do these tests at your own risk. The club nor myself accept responsibility for errors you make or any consequences arising. Note This is for Diesel variants only

[t_i_m]

Should the Aircon be on for this (i.e go from low speed to high speed) or work whatever?

I have tried this on my 04 with I assume a 3 speed fan (no resistor), but nothing happens, I have tried with ATC on auto and off.
I assume there is enough gas as it gets very cold?

I have always wondered what the high speed is like because the low speed is very loud (and has been like that since I bought the car with 17,000 miles on).

Thanks
Tim

[Jules]

Yes Tim
Set the Aircon to the demist function (this overides the outside temp) or set the temps to LO Or make sure the inside temp is set 12 Deg C lower than the outside temp.


The cooling fan will operate even if there is no gas in the system, or with the Trinary disconnected, only difference will be the compressor solenoid won't be energised. (via small Relay No7 engine fuse box)
The fan should will come on SLOW speed for 2 speed fans & LOW speed for 3 speed motors (diesel variants)

Then with the Yellow/Grey & black wires shorted the HIGH speed will kick in.

Testing the Aircon A/C compressor solenoid Engine running
The other test you can do if the compressor doesn't seem to be kicking in is is to short the 2 Red/Black wires on the same Trinary plug. (this may prove whether there's any gas in the system or not)

If the compressor now runs, the likely hood is you need to get an A/C specialist to do a leak test & then a re-gas.

Do not attempt to get Air conditioning functioning until you are satisfied all the cooling fan speeds are working. Compressor damage will occur if insufficient cooling for the condensor & more importantly the engine!

[t_i_m]

Thanks for clearing that up Jules - I will try again in the morning.

I just tested the two contacts on the switch for the black/red wires (low pressure switch) and they are open circuit. I assume by the following statement that is correct (they go short circuit when the pressure drops)?

Testing the Aircon A/C compressor solenoid Engine running
The other test you can do if the compressor doesn't seem to be kicking in is is to short the 2 Red/Black wires on the same Trinary plug. (this may prove whether there's any gas in the system or not)

If the compressor now runs, the likely hood is you need to get an A/C specialist to do a leak test & then a re-gas.

I was expecting them to need to be short circuit after reading Keiths comments in post#10 (which I appreciate is a very old thread)?

http://www.the75andztclub.co.uk/foru...ead.php?t=1145

Thanks for the help

Tim

[Jules]

Agree Tim!

The Red/Black trinary contacts are normally "Closed" (with gas in) to enable Relay 7 to energise the solenoid ...........hence why my Test works
The Grey/Yellow contacts are "Normally open" and excess Temp causing excess pressure closes them bringing in HIGH SPEED FAN.
If a gas leak occurs, insufficient Gas pressure causes the RED/BLACK trinary contacts to OPEN thereby disabling the solenoid via Relay 7.
End result is that the compressor is disabled when no gas

[Jules]

Keith's statement agrees with mine on LO pressure Trinary state, but I don't agree with his HI pressure state.

[t_i_m]

Sorry I have been confusing things by using the wrong terminology (reversed) so just to confirm when you say:

The Red/Black trinary contacts are normally "Closed"

You mean the two contacts are connected, which is what I have (I get zero resistance). The high pressure contacts should be normally "open" i.e. not connected -again what I have (I get infinate resistance).

So I think I am ok. - Everything seems to work ok. I just still need try my high speed.

[Alex30013k]

I have just tried this and nothing happens, you can hear something clicking near where the resistor is in the bumper.

I have not heard my fan in ages, it was fully replaced about 2 years ago and has not worked for well other a year,

[James.uk]

When Jules tested my fans during a semi social visit, he concluded that they were not working at all..

So I arranged a 2nd visit to make sure. And that proved to be the case when he actually dissmantled the front end and examined the fan motor, it had clearly not worked for some time! ..

I had Jules replace the motor and carry out his full £450 service, and it proved excellant value for money as several more faults were discovered and corrected.

PS, The biscuit tin failed to appear though.. lol..
.

[Jules]

Blumin cheek James I left the tin on the swing chair. Perhaps it fell into Jeff's toolbox or John scoffed the lot

Alex it sounds like you have no speeds at all.
Have you checked the 80 Amp fan fuse in engine compartment ?
Could be a cable join, in the fan loom, or control box relay earthy side but very unlikely it's both relays. BTW the 12 Volts is unswitched straight to the motor.
It's the Earth line that gets switched through the resistor (LOW speed) or bypasses it for HIGH speed.

Scenario 1
So the relays have got supply to their primary coils (the clicking you can hear), but it could be that the main 80 Amp supply (perm unswitched 12Volt) has been lost.
This is fed via thick brown cable in the fan harness which then has a cable joint on to a red cable just a few inches before the motor.

Scenario 2
The earth path may have been lost from the chassis point P1355-1 (ring terminal on passenger side inner wing) or lost in the motor harness before the main relay contacts. I can't imagine the earth path has been lost after the relays as it follows 2 different paths (either via resistor or straight to motor)


The above fault finding is for the later 2 speed set up. The older 3 speed motors work very differently
ie The the 12 Volts (on brown wires) is switched through different field windings within the motor.
The earthy side is effectively fed directly to the single earth brush.