Technical Heater fan issue

[Malc]

2004 2.8JTD X244 Hymer Motorhome.
Hi. Just been away for a couple of months and heater fan speed switch was a little temperamental on fan working on all speeds. Now just stopped totally!
Not had time investigate yet, but assume fuse blown as a starter.
Do these symptoms sound like the resistor unit, I understand to be a common problem? Or anyone got an idea as to what's faulty.
Thanks.

 

[Communicator]

2004 2.8JTD X244 Hymer Motorhome.
Hi. Just been away for a couple of months and heater fan speed switch was a little temperamental on fan working on all speeds. Now just stopped totally!
Not had time investigate yet, but assume fuse blown as a starter.
Do these symptoms sound like the resistor unit, I understand to be a common problem? Or anyone got an idea as to what's faulty.
Thanks.

The resistor is not used at fan speed 4. Fuses are not intermittent, but could have a bad connection.
I am generally sceptical when relays are suspected, but the heater fan is a large electrical load, and a failure of the appropriate relay has been reported.

For a basic heater fan see my diagram attached, although it is slightly customised it should suffice for basic checks.. Check F55 (green), if OK, then try red relay from position T01 in place of red relay T12.

If the vehicle has cab aircon, then there are more relays under the bonnet. The copy of eLearn diagram E6020 that I have does not make sense, and may include several errors.

 

[Malc]

The resistor is not used at fan speed 4. Fuses are not intermittent, but could have a bad connection.
I am generally sceptical when relays are suspected, but the heater fan is a large electrical load, and a failure of the appropriate relay has been reported.

For a basic heater fan see my diagram attached, although it is slightly customised it should suffice for basic checks.. Check F55 (green), if OK, then try red relay from position T01 in place of red relay T12.

If the vehicle has cab aircon, then there are more relays under the bonnet. The copy of eLearn diagram E6020 that I have does not make sense, and may include several errors.

Thank you for the info.
Just to clarify, the fan was intermittent on all speeds, until yesterday when nothing, assuming that was fuse.
Its bouncing down this morning so will have to look later. Thanks

 

[Malc]

Just had a look at the resistor unit. Does this look standard? The wires look to have crimped spade end connectors into the brown unit, not a plug in as I've seen on some videos. F55 looks good. Swapped the relays and still no fan.

 

[Communicator]

Speed control resistor failure, typically affects any/all of speeds 1, 2, & 3, with 4 remaining OK.

 

[Malc]

Speed control resistor failure, typically affects any/all of speeds 1, 2, & 3, with 4 remaining OK.

Thanks, appreciate that, was interested to see it, but doesn't look standard connection. Swapped the relays and still no fan.

 

[jackwhoo]

Just had a look at the resistor unit. Does this look standard? The wires look to have crimped spade end connectors into the brown unit, not a plug in as I've seen on some videos. F55 looks good. Swapped the relays and still no fan.

In pic silver cylinder at bottom of pic is a thermal fuse ....if it "blows" you may get no fan. Use mulitmeter on "tails" to check not open circuit.

 

[Communicator]

Just had a look at the resistor unit. Does this look standard? The wires look to have crimped spade end connectors into the brown unit, not a plug in as I've seen on some videos. F55 looks good. Swapped the relays and still no fan.

Having found time to examine photo of resistor unit more closely, the connections are not OEM. This does not mean that they are the cause of the problem. It is possible that the change was made during a previous repair. I am rather puzzled by the fact that red crimp connectors seem to have been used, as these are only suitable for conductor csa not exceeding 1.5sq mm. eLearn quotes 2.5sq mm for the fan wiring, and this would require blue crimp connectors. If the wiring has been reduced in csa, it will be less able to conduct heat away from the actual connection.

 

[Communicator]

In pic silver cylinder at bottom of pic is a thermal fuse ....if it "blows" you may get no fan. Use mulitmeter on "tails" to check not open circuit.

A blown fuse, whether thermally, or current operated, would not make the fan operation temperamental.

 

[Communicator]

@Malc ,

1. Do you have, and are you able to use a multimeter?

2. As I previously mentioned, does the vehicle have cab aircon?

3. Also worth checking fuse F31, at top LHS corner of LHS cab fusebox, B002. (Quick check, do reversing lights work?)

 

[Malc]

Yes, i do use a multi meter.
Yes, does have aircon. It was working OK the previous day, but wasn't on when fan failed.
Yes, just checked, reverse light working.

 

[Communicator]

Yes, i do use a multi meter.
Yes, does have aircon. It was working OK the previous day, but wasn't on when fan failed.
Yes, just checked, reverse light working.

The problem could be with the speed switch, the fan motor, or elsewhere. For the basic fan circuit the circuit in order of connection is, 70A maxi blade fuse in engine bay, relay T12 contacts, fan motor, speed resistor, speed switch, earth.
With ignition on, and fan switched off, you should be able to measure 12V between any point on resistor and earth, but do be aware that the sensitivity of modern multi meters allows them to show a credible reading through a high resistance. A possible further check would be to replace the meter with a short circuit to earth. To avoid burning yourself, any wire used to create the short should be at least 1.5mm for a quick application. If you can manage this safely, and the fan runs, it would prove that the motor is OK.

I am attaching my corrected version of the basic fan wiring, for illustration only. The Air Conditioning diagram E6020 can be viewed here. As I stated earlier it has errors. On relay J022 the contacts are incorrectly labelled. For 87A read 30, for 30 read 87, and for 87 read 87A. Then it may make sense. Another error may be with the connections to relay J041, but as my x244 did not come with aircon, I have not looked very closely.

Edit. Relays J034, J041, and J022 are located under the small hood in the engine bay. The fourth relay in there is for the flame starter glowplug. Some converters fitted split charge, and fridge relays in that location.