Cooling fan stuck on. - Page 3

stocktake · 29th April 2015, 06:53

Quote:

Originally Posted by davidcarp

Can the PCB be changed separately and where is it or do I have to get whole fan assembly? I've had the car for 5 years and don't think the other fans have ever worked ( I've done the 'demist on check' but the fan doesn't come on. I check the temp when driving and goes up to about 87 degrees. Ill have to get the work done for me. What would be involved?Thanks

It would appear David that Simon has your problem in hand on your other thread, you won't go wrong with his advice. Jumping on another persons thread will only cloud the water for you.

davidcarp · 29th April 2015, 07:08

Quote:

Originally Posted by stocktake

It would appear David that Simon has your problem in hand on your other thread, you won't go wrong with his advice. Jumping on another persons thread will only cloud the water for you.

Thanks for your assistance

HarryM1BYT · 29th April 2015, 07:10

Quote:

Originally Posted by philfatkid

i thought i had cracked it, but oh no, as i was poking around i found that the gold resistor i had fitted a few years ago had been blown to s**te, the post had been blown out of the middle

That exploding resistor issue has happened before. Assumption was - that the resistor wasn't properly sealed, water had got in, then the heat had turned the water to steam. The steam built up a lot of pressure, enough to blow the resistor apart.

Best advice is make sure the resistor is a genuine good quality replacement item.

philfatkid · 29th April 2015, 11:46

Update 2,
Fitted the new resistor, tested the high speed relay (as per SD1too's instructions) this was fine, tested the fan via the demist route, it still didn't work, checked the low speed relay, found it wasn't latching (coil knackered) swapped it for the unused one next to it, and low and behold it worked when tested via the demist route.
My questions are,

1, When i first tested the fan yesterday, after changing the high speed relay, the fan didn't work at all, (this is after originally the fan being on constantly on fast speed, even when ignition was turned off) SD1too said it should have pulsed at high speed, is the reason it didn't, because the low speed relay was u/s ?
2, Is there any way i can test the high speed function, like you can test the low speed (demist test) ? because i don't fancy putting the Blue beast back together only to find the fan doesn't work on fast speed.

Phil D.

SD1too · 29th April 2015, 12:29

Quote:

Originally Posted by philfatkid

1, When i first tested the fan yesterday, after changing the high speed relay, the fan didn't work at all, (this is after originally the fan being on constantly on fast speed, even when ignition was turned off) SD1too said it should have pulsed at high speed, is the reason it didn't, because the low speed relay was u/s ?

Until the other day I would have said that the low speed relay wouldn't affect high speed operation (on a resistor system), but I'm finding out that the diesel system moves in mysterious ways. Another member had the same problem as you; continuous running of the fan whether air con. was on or off. As part of our investigation the coolant temperature sensor was unplugged. When refitted, the fan had stopped running continuously and when the air con. was subsequently recharged the system worked perfectly.

In your particular case, if the low speed relay coil was open circuit the ECM would be able to detect that. It's therefore possible that it could inhibit the fast speed, although that would be totally illogical. However we are talking about computers here!

Quote:

2, Is there any way i can test the high speed function ..

Yes. Remove the trinary switch electrical connector and join together pins 2 (black wire) and 3 (yellow/grey wire). The high speed fan should then be triggered. Your air conditioning will probably have to be charged and in working order for this test to be reliable.

Well done for fixing your own car. Unfortunately it looks like that's another beer I owe to Stocktake.

Simon

philfatkid · 29th April 2015, 12:38

Quote:

Originally Posted by SD1too

Until the other day I would have said that the low speed relay wouldn't affect high speed operation (on a resistor system), but I'm finding out that the diesel system moves in mysterious ways. Another member had the same problem as you; continuous running of the fan whether air con. was on or off. As part of our investigation the coolant temperature sensor was unplugged. When refitted, the fan had stopped running continuously and when the air con. was subsequently recharged the system worked perfectly.

In your particular case, if the low speed relay coil was open circuit the ECM would be able to detect that. It's therefore possible that it could inhibit the fast speed, although that would be totally illogical. However we are talking about computers here!

Yes. Remove the trinary switch electrical connector and join together pins 2 (black wire) and 3 (yellow/grey wire). The high speed fan should then be triggered. Your air conditioning will probably have to be charged and in working order for this test to be reliable.

Well done for fixing your own car. Unfortunately it looks like that's another beer I owe to Stocktake.

Simon

Sorry for your loss Simon

as a matter of interest where is the trinary switch located ?
Phil D.

philfatkid · 29th April 2015, 13:58

Ok Simon,
Update 3, found the trinary switch, shorted out the black and yellow wires, the fan came on but only at slow speed ?
Phil D.

philfatkid · 29th April 2015, 15:03

Update 4,
Energised the high speed relay with 12v and the fan came on at high speed ?
Phil D.

SD1too · 29th April 2015, 18:00

Quote:

Originally Posted by philfatkid

...found the trinary switch, shorted out the black and yellow wires, the fan came on but only at slow speed ?

There's something not quite right here.

Quote:

Originally Posted by philfatkid

Update 4,
Energised the high speed relay with 12v ..

How did you do that?

Simon

philfatkid · 29th April 2015, 18:26

Quote:

Originally Posted by SD1too

There's something not quite right here.

How did you do that?

Simon

Took the relay out of the control box, connected the cables to the fan, then put 12v on to the coil, simples

Do you think it might be the PCB now ?

29th April 2015, 13:58	#27
philfatkid Loves to post MG ZT Join Date: Oct 2010 Location: Newton-le willows Posts: 267 Thanks: 1 Thanked 11 Times in 11 Posts	Ok Simon, Update 3, found the trinary switch, shorted out the black and yellow wires, the fan came on but only at slow speed ? Phil D. Last edited by philfatkid; 29th April 2015 at 15:02..

29th April 2015, 11:46	#24
philfatkid Loves to post MG ZT Join Date: Oct 2010 Location: Newton-le willows Posts: 267 Thanks: 1 Thanked 11 Times in 11 Posts	Update 2, Fitted the new resistor, tested the high speed relay (as per SD1too's instructions) this was fine, tested the fan via the demist route, it still didn't work, checked the low speed relay, found it wasn't latching (coil knackered) swapped it for the unused one next to it, and low and behold it worked when tested via the demist route. My questions are, 1, When i first tested the fan yesterday, after changing the high speed relay, the fan didn't work at all, (this is after originally the fan being on constantly on fast speed, even when ignition was turned off) SD1too said it should have pulsed at high speed, is the reason it didn't, because the low speed relay was u/s ? 2, Is there any way i can test the high speed function, like you can test the low speed (demist test) ? because i don't fancy putting the Blue beast back together only to find the fan doesn't work on fast speed. Phil D.

29th April 2015, 15:03	#28
philfatkid Loves to post MG ZT Join Date: Oct 2010 Location: Newton-le willows Posts: 267 Thanks: 1 Thanked 11 Times in 11 Posts	Update 4, Energised the high speed relay with 12v and the fan came on at high speed ? Phil D.