heater fans not working

chinaman20 · Postby **chinaman20** » Thu Jul 10, 2008 7:54 pm

Hi, i have a problem with my 85 v12 with the fans not working at all.I have checked and replaced fuses just in case but they are ok. The aircon does not work, but since the car was laid up for 10 years i suspect it needs regassing.
Do you have to have the aircon working for the fans to work?
Any help would be most welcome.

almcl · Postby **almcl** » Thu Jul 10, 2008 9:53 pm

The air con doesn't need to be working and after ten years it may need more than a regas, but the fans won't blow in low or auto until the coolant warms up. They should work in high or defrost, however.

If they don't, then check for voltage on the fan speed relay (largish silver box low down on the left hand side of the heater unit) 12 v should arrive via a Brown/white and leave via a green/slate.

If voltage is getting to the green slate but the fans aren't running, it might be worth disconnecting the harness and jump wiring the fan directly to a 12v supply to see if they can be shocked back to life.

chinaman20 · Postby **chinaman20** » Thu Jul 10, 2008 11:06 pm

Many thanks for the reply and help, will give it a try this weekend.

chinaman20 · Postby **chinaman20** » Sun Jul 13, 2008 12:44 pm

The air con doesn't need to be working and after ten years it may need more than a regas, but the fans won't blow in low or auto until the coolant warms up. They should work in high or defrost, however.

If they don't, then check for voltage on the fan speed relay (largish silver box low down on the left hand side of the heater unit) 12 v should arrive via a Brown/white and leave via a green/slate.

If voltage is getting to the green slate but the fans aren't running, it might be worth disconnecting the harness and jump wiring the fan directly to a 12v supply to see if they can be shocked back to life.
Hi, done as you advised and i am getting 12v in via brown/white but nothing on the green/slate.Jumped the fans with 12v and they work.
I cannot see a silver relay, just a black box with those connections and several others. Is this the relay?

almcl · Postby **almcl** » Sun Jul 13, 2008 10:34 pm

Sounds as though the relay could be faulty, but don't jump to that conclusion just yet.

To be quite sure, the relays are housed in the item numbered five on this diagram:
http://www.jec-xjs-forum.org.uk/xjsbb2/ ... 4-1_tn.jpg

while it is quite likely that the relay is faulty, there are some other things to check; the thermostatic switch (no 3 in the diagram) short the leads on this together; the brown yellow wire on the relay box should also have 12 volts, if it doesn't then there's a switch fault or a harness break.

If there's 12 volts on the relay's Y terminal then the resistors or their wiring may be faulty.

ng4xjs · Postby **ng4xjs** » Mon Jul 21, 2008 1:30 pm

Sounds a bit like the transistor pack has gone down. One for each fan.

Nick

almcl · Postby **almcl** » Mon Jul 21, 2008 10:01 pm

It's an '85, Nick, no transistors!

chinaman20 · Postby **chinaman20** » Wed Jul 23, 2008 8:24 pm

It's an '85, Nick, no transitors!
I had a look and no transistor packs on it, but i have no volts on the brown/yellow wire so a wiring/switch problem looks likely. I will have to be brave and centre console out to get at switch.

chinaman20 · Postby **chinaman20** » Wed Aug 06, 2008 4:23 pm

Just like to say thanks to all for the advice and ideas, traced the fault to a bad connection on a fuse under the dash. All working now!
Many thanks to all.