Cooling Fan Not Running

[silverswitch]

Hello all, just looking or a little help here. I browsed through some previous posts on this topic but couldn't find what I was looking for. Basically cooling fan will not turn on when engine is too hot and will also not turn on when AC is on. I replaced Cooling Fan no. 2 relay in the fuse box on driver's portion of the car thinking that was the issue. No go. I tested the fan by connecting directly to battery and it spins so I think the fan is good. I believe the manual stated that a faulty temp sensor can cause this so I replaced that as well. No go. At this point the only thing I know I haven't replaced is the Cooling fan no. 1 relay and the cooling fan resistor. If any of you have any specific threads to reference that I may have missed or some words of wisdom here I'd really welcome it. I'm coming dangerously close to just hard wiring this fan to a switch (I will regret it). Thanks.

[atomic_hoji]

So the fan doesn't come on at all and you're getting the overtemp light on the dash? Probably not worth the nuisance of hard-wiring the fan to a switch - it'll just take forgetting one day and finding the battery flat to regret that. :biggrin:

The fan control circuit goes through No.1 relay first and then to the No.2 relay in the de-energized state to the Cooling Fan Resistor then ground for low speed. For high speed the No.2 relay is energized, which bypasses the Cooling Fan Resistor and goes to ground. If your No.1 was good and No. 2 bad then I would imagine your low speed fan would be working, just not your high speed. But, if No. 1 is bad then the relay failing to energize cuts off power entirely, so you have no fan speeds. Maybe try swapping the known good relay into the No.1 spot, then try each of the other questionable relays in the No.2 spot and see what you get; once the car is running good and warm obviously.

After that my guess is a bad ground connection somewhere; not sure that's the case, depending on how you tested the fan operation that might disprove that idea. Possibly a combination of multiple failed relays and/or other components. Possibly the ground for the ECM or the ECM itself has a fault - although if there's no suspect reason, e.g. shorted something, water soaking the ECM, etc.., then it seems a stretch for that to be the issue.

Give it a whirl and see if you have some luck.. Let us know what you find.
-- Adam

[silverswitch]

Thanks for input. I know I've replaced the no.2 relay but I haven't the foggiest where the no.1 is. Are they interchangeable? It's entirely possible there is a bad ground somewhere. I tested the fan off of the vehicle directly using some extra wire I had. I took a peak at a wiring diagram I found online and it kind of looks like the cooling fan relay no.1 is on the passenger side but not entirely sure. Only thing I saw over there was a much larger relay. Couldn't really find anything other than the relay no.2 online (autozone etc.). I'm definitely not wanting to walk down the path of bypassing these relays to a switch so I was only half serious but I'd like to explore everything I haven't tried first. I really appreciate the help on this one.

[atomic_hoji]

No problem. I just ran out to the garage as I have a 2007 Yaris Hatchback main junction box, but unfortunately I couldn't find the lid and it doesn't have labels - routing the wiring underneath wasn't as helpful as I thought either.. :rolleyes:

If you check the inside cover of the main junction box lid it should list the relays - in my 3rd gen. the 2 fan relays are right beside one another. The 2007 looks like it is the same sort of setup, but I don't have labels.. Googling now, lol.

The No. 2 relay differs in that it has 2 wires coil side and 3 wires switch side, where-as the No. 1 relay has 2 and 2 - this is because it only uses the switch in the energized state. If you put a No. 2 relay in the No. 1 spot I don't see why it wouldn't work - there's just no wire for the de-energized state connected. You wouldn't get the correct function if you tried to put a No. 1 relay into the No. 2 spot - it would only function on high speed when the relay is energized, low speed wouldn't have a switch connection to the Cooling Fan Resistor.

A quick Google search I see AutoZone carries both types of relays, but can't find a decent relay diagram..

-- Adam

[atomic_hoji]

Well crap.. http://www.yarisworld.com/forums/showthread.php?t=40023

I apologize, from looking at my 3rd gen. and the description of the 2nd. gens I thought it was the same. In the post linked CTScott - well known guru of Yaris knowledge - points out that the No. 1 fan relay is part of the integrated relay. No wonder can't find a diagram.. :rolleyes:

If that is the same style as the 3rd gen. then the relays will be surface mounted to a printed circuit board inside the unit. Can't easily swap a relay on to test it out.

-- Adam

[silverswitch]

Just grabbed the cover off mine. Should be a pic below. I still am only seeing one cooling fan relay listed (no.2) unless I'm losing my mind.

[atomic_hoji]

Oh. Quick other thought before I head off tonight - have you checked the fuse? Might seem obvious, but something easily overlooked? Just a thought..

-- Adam

[ezhacker1]

Ground is common to both Relays, id check that by going backwards, you can always force the relay to close to mimic both ECU controlled and Radiator Fan Resistor tripping.

[ezhacker1]

FanNo1 Relay is in the integreated Relay that is the one that has fuses EFI / HORN / AM2 / FAN NO1 Relay

[silverswitch]

I appreciate all the help. No wonder I couldn't find the damn thing. Just found CTScott's post as well back in 2015. This gives me a great place to start. Thanks all.

[atomic_hoji]

Let us know what you find and you solved it. :thumbsup:
-- Adam

[silverswitch]

Well, first and foremost I'd like to thank anyone who took the time to help me out, even if I did noob it up and ask for information that had been requested and covered here before. With all the help I was able to get it going. I'd like to say it some crazy goofy grounding issue that took hours to find but alas that is not the case. Apparently I'm a moron. It was the 30a RDI fuse that did the trick. I should have done way more digging on just fuses first. At any rate, I appreciate all the help and I learned a whole lot more then I knew before about how these jokers are wired. Thanks again all.

[atomic_hoji]

lol - all good. Glad it was something straight forward and you're all fixed up. :thumbsup:
-- Adam

[zoidberg444]

Well, first and foremost I'd like to thank anyone who took the time to help me out, even if I did noob it up and ask for information that had been requested and covered here before. With all the help I was able to get it going. I'd like to say it some crazy goofy grounding issue that took hours to find but alas that is not the case. Apparently I'm a moron. It was the 30a RDI fuse that did the trick. I should have done way more digging on just fuses first. At any rate, I appreciate all the help and I learned a whole lot more then I knew before about how these jokers are wired. Thanks again all.

Great news mate. Just bear in mind that fuses generally pop for a reason. I've seen instances where worn out motors begin to pull more current than they should. Something to consider if the fuse pops again.

[silverswitch]

Great news mate. Just bear in mind that fuses generally pop for a reason. I've seen instances where worn out motors begin to pull more current than they should. Something to consider if the fuse pops again.

That's actually really good to keep in mind. The kid that owned this prior to me had ghetto rigged up LED bar lights on the roof and on the bumper. The wiring looked like my 10yo did it. Strike that, he could do it better. I should probably go back through and make sure it's all sound. Thanks for the heads up.

[Nkwabi]

Hello all. I am in need of your help. I have a 2006 Vitz/Yaris, 1.3 litre, 3 cylinder. I have a problem with the radiator fan. It will not switch on when i turn the A/C system on. It works fine else where when it needs to be on to cool the engine. Plus the engine shakes tremendously when the A/C is on, to the point when the engine cuts off. Please help, i have replaced the compressor, radiator and cleaned the whole system but it still continues.