Hi speed cooling fan trouble

[Brett_jjj]

My Hi speed circuit on the cooling fan wont work,the low speed one works though.It comes on with the AC,it comes on at half way like usual when sitting idling,but when I unplug the temp sensor wiring from the temp sensor it wont go from lo speed to high speed like it should,it just stays on low speed.It should(once disconnected) after 12 seconds turn on to low speed,then after around 6 seconds go to hi speed.I have swapped relays etc,no difference,checked the engine fan fusible link,all ok.I connected 12 volts to the fan,tried it on both pins in the plug and it worked fine.This one has me stuffed,am I missing something.

 

[RX25SE]

Relay clicking when it tries to cut in?

Are you getting temp readings and fan relay status from the tech 1?
Can the tech1 do and actuation test?

I've seen a bad earth near the battery, the one on the inner guard, preventing the hi fan from coming on.

 

[Brett_jjj]

No relay noise at all.The Tech 1 was how I found out it wasnt working.It just commands the lo and hi speed fans on or off.Temp readings are fine.The lo speed works fine,just no hi.I will check out the earth youve mentioned and see what I find.

 

[Brett_jjj]

Well, no difference.The earth is clean and tight,I loosened it and tightened it again just to be sure of a good contact.Still no hi speed.Battery terminals are also clean.The Tech 1 cartridge I have has no menus for fan relay status.Just fan on or off.Hi or lo.

 

[hako]

Maybe you have a problem with your cooling fan motor or the wiring to the motor/relays - when the A/C comes on it switches the high fan on according to the manual. You say that it switches the fan to low??? When you hotwired the fan did it work at 2 speeds? (you dont specifically mention this).
I know these 2 speed fans wear out because my wrecker removes them from the wrecks and stores them in the office.

 

[Brett_jjj]

It just sounds like its on low speed all the time.(usually fairly noisy on hi speed)Even when hotwired it didnt seem to change much which I just put down to the way Id connected it to the battery,(used thin little wires as jumpers),but the two different terminals in the fan plug both worked.I might get another fan and try it.I thought the AC turned the low speed fan on ,maybe its just going to hi and not lo.Althought when I connected up the tech 1 and command fan on/off, it turns the low speed on,but wont turn the hi speed on.

 

[hako]

What happens when you pull the hi or lo speed relay out?

 

[Brett_jjj]

I will go and try it.

 

[Brett_jjj]

I started the engine and removed the lo speed relay,nothing,so replaced that,and removed the bigger hi speed relay,nothing,so I removed them both,nothing at all.Not even on at low speed.I gave it a while with each relay removed too.I know it was working a month or two ago,It was going from lo to hi no problem when the sensor wiring was removed,and nothing has been stuffed around with at all.Nothing has been touched.

 

[hako]

I reckon it's that Tech 1 you bought off Ebay...get rid of it....to me. :smoking:
Fusible links?