radiator fan not coming on

[idosubaru]

radiator cooling fan does not come on at all.

 

relays, fuses, fans, are all good.

swapped in another CTS in the radiator.

 

how do i test? should the pins of the CTS connector always have continuity/12 volts?

the CTS should have continuity when it's hot right - to complete the circuit and trigger the fans?

[unibrook]

is the CTS the thermoswitch?

How do you know your fan is ok? Have you made it turn on by turning on your AC and Fan cabin switches?

 

If so, and if you want to see if the thermoswitch has failed: disconnect the single wire (yellow?) coming out of the back of the thermoswitch at its connector point....probably 5 inches away from the radiator. Put a piece of wire into the connector coming from the harness, turn the key to ON (don't need to start engine), turn AC to ON and Fan to ON, then touch the wire to the radiator ground screw. Your cooling fan should turn on, since this completes the circuit to ground. (and this will imply the problem is your Tswitch).

 

Does this make sense? or am I missing your prob?

[idosubaru]

thanks. yep, you're on it. forgot to mention - it's an XT6. i gave the fans 12 volts and they came on - so the fans should be good.

 

XT6 thermoswitch has two electrical contacts, not just one.

 

so - that circuit, when the car is on, should always have 12 volts right - the plug that plugs into the thermoswitch?

 

that makes the system really simple:

12 volts, a CTS to complete the circuit, and the fans.

 

is that it?

 

the fan relay (XT6 has two electric fans) is only for the A/C fan?

[unibrook]

since that Tswitch is diff from the one I just tested on our 1982 GL (ours had only one wire coming out of it) then I am afraid I can't offer any good advice on how it is supposed to work...ie, at what temp etc.

 

does that fan come on with your AC and Fan controls turned on?

 

If so, I am guessing your Tswitch is faulty.

[idosubaru]

fans never come on. a/c does not work, it's not charged, so that won't trip it. i should charge it up and see if that will turn them on, thanks, that might tell me something.

[unibrook]

I think you can test your type of Tswitch by removing it from the radiator. Boil some water, put the threads of the Tswitch into the water, and test the wires with your multi-meter for continuity. I think that is basically what you were saying anyway, yes, that should work for a test.

[hooziewhatsit]

With the two wire thermo-switch, if they're like the one on my 88 GL, unplug it from the thermoswitch and stick a paper clip in the plug to short the wires together, turn the key on, and the fan should turn on. Basically so you're bypassing the thermoswitch.

[Mantis_Toboggan]

If all your components are good, but the fan is not turning on, you could always build your own harness.

[themoneypit]

gary, pretty sure theyre are several relays for the fans. on the pass side in front of the strut tower there should be 3 of them. two side by side, one underneath those. not sure which does what, maybe try switching them up and see if you have any luck.

[GeneralDisorder]

Have you bothered to wire the fan up directly to a 12v source to see if the fan even works? You might be hunting a problem in the wireing that doesn't exist.....

 

Basically - the fan should always have 12v - it's a ground controlled circuit. If you have voltage to the fan then you need to check the ground side and see where the circuit is broken. If you don't have voltage to the fan then you need to find out why.....

 

You can just short across the connector to the thermoswitch and the fan should fire up - it just completes the circuit across it (to ground I beleive) when it hits it's trigger temp.

 

GD

Edited September 2, 2010 by GeneralDisorder

[Yo'J]

How bout this..... can you feel the wires in the harness that rub on the battery shelf? Its where the crimp is for the power I believe. That is a very messed with wire in that bundle. You always move it for an overhaul of almost any kind.

 

Im about to strip the whole thing a foot in either direction and repair every wire I got probs with. I got a rainy day short and no side markers and a fan you wiggle that same wire to turn on. I've gotta do it this week.

 

Your in an xt? It shouldnt be so different from my wagon.

[idosubaru]

Okay test results:

 

when jumping the CTS sensor for the fan: it does not come on.

 

when given 12 volts the fans come on just fine. so the fans work.

 

all fuses are good, i swapped the 3 relays around so unless all three are bad (highly unlikely), that shouldn't be the issue - though i'm not sure the cooling fan even has a relay (i thought only the A/C fan had a relay)?

 

anyone know what the next test would be?

[GeneralDisorder]

Find out which fuse supplies power to the fan and check that you *have* power on both sides of it.

 

Then find out for sure if it has a relay or not and which one it is. Then you can check for power at the relay, and if the relay is closing or not with the ignition switch. You can easily check the relays with some jumper wires and the battery - just touch the coil terminals to the battery and see that it closes and has continuity between the contact terminals.

 

GD

[idosubaru]

Find out which fuse supplies power to the fan and check that you *have* power on both sides of it.

i did check that but i didn't want to confuse - because i wasn't sure if it was supposed to have power. i checked the other circuits - like headlights, etc and those fuses did not have power until i turned the headlights on. so i would assume that maybe this circuit doesn't have power until the CTS completes or "turns on" the circuit?

 

it didn't have power...but neither did the headlight fuses, which worked fine.

 

i guess it "should" have power if i jump the CTS connector, but without the fans coming on i bet it won't...but who knows.

 

i agree, wiring diagram is a necessity at this point.

Edited September 4, 2010 by grossgary

[NorthWet]

You do not have a wiring diagram? I am not sure if one would help... and I am pretty sure that the 2 in my 88 FSM wouldn't help: They seem to contradict each other. A "simplified" whole-car diagram implies that the fan is connected to power through fuse#15, and the motor has 2 parallel ground paths, one being through the thermoswitch and the other through the A/C relay.

 

The A/C section gives a "more detailed" diagram that shows the fan motor being unswitched to ground and the thermoswitch activating a relay to supply power to the fan motor, and what looks like a separate relay used for a secondary, A/C fan motor.

 

...You can just short across the connector to the thermoswitch and the fan should fire up...

 

Even with a brand new thermoswitch, my Xt-4's fan didn't seem to work right if at all, so I would just run a jumper like GD suggested.

[idosubaru]

You do not have a wiring diagram? I am not sure if one would help... .

exactly what you said. i couldn't find the main cooling fan. i saw the power take off and bit of other cursory info but nothing specific. strange you saw the same, i figured i just missed it.

 

The A/C section gives a "more detailed" diagram that shows the fan motor being unswitched to groun

i don't think i saw that when i was looking. i was ignoring that because i figured the sub fan (for A/C) and main would be separate.

 

so if i wanted to wire this thing....i'm slow with electronics...could i give 12 volts to the two terminals at the CTS and see if that turns the fan on?

 

if it does then i can power one side of the CTS, ground the other, and i've got a working system again right?

 

guess it's not really much more work to just power the fan while i'm doing it? duh?!

 

thanks guys.

[Mantis_Toboggan]

I just realised that I forgot to include fuses. 15A on each power wire as close to the power source as possible.

[GeneralDisorder]

That's not how it's done - the temp switch is a ground control - there is ALWAYS power to the fan (through fuse #15 apparently [Gary - have you checked for power on both sides of this fuse?]). The other lead to the fan goes to the temp switch and then the temp switch closes and shorts it's fan lead to ground. That completes the circuit and starts the fan. There is another path to ground though the AC relay's but if you have no power at either of the fan leads - none of that "downstream" stuff will work. They build stuff this way so that power leads that can short to ground are as short as possible and if a component fails internally, it's on the downstream side of the load and doesn't blow fuses. So if the temp switch were to fail and short itself to ground - all that would happen is the fan would come on and not go off - instead of blowing a fuse, overheating, etc.

 

Sounds to me like you have a bad power lead to the fan (or the fan fuse) - if that's the case then you only need to run a new wire from fuse #15 to the fan lead (whichever one doesn't have continuity with the temp switch).

 

Gary - do you have a multi-meter?

 

DO NOT put voltage to the temp swich connector. You will create a direct short to ground and burn something up. It is not located on the supply side of the load (fan).

 

Bypassing the stock wireing is the LAST resort here. And replacing as little of it as possible is the goal. First we need voltage to the fan. Solve that problem and see where you are at.

 

GD

Edited September 5, 2010 by GeneralDisorder

[Mantis_Toboggan]

DO NOT put voltage to the temp switch connector. You will create a direct short to ground and burn something up. It is not located on the supply side of the load (fan).

 

Bypassing the stock wiring is the LAST resort here. And replacing as little of it as possible is the goal.

GD

 

Be sure not to over look these

[idosubaru]

yes i have a multi-meter...keep in mind my skills at using it are waaay behind my other mechanical familiarity.

 

AH HA - so i just tested it wrong, like stuck the MM in each leg of the fuse - that's not how to test it i see now, obviously that circuit isn't working so duh i didn't get anything! I can test each SIDE of the fuse...or more correctly just the power side by testing the power side and putting the other terminal to any ground. the fuse should always have power but necessarily be grounded?

 

Fuse has two legs - I can test for 12 volts on one side (so to speak), right?

 

I'll do that next, thanks guys.

 

I totally would have given that connector 12 volts, i'm glad you said that. I have no qualms about "learning the hard way"! Thanks again for helping out the electrically inept!

[GeneralDisorder]

The meter is going to give you a measure of voltage "potential" - that is you are not looking for voltage that is flowing, but rather that there exists a higher voltage on one side of the meter than the other. This is important. If you test using both legs of the fuse then you will get a 0 reading if the fuse is good. That means either that there is no voltage on either side, that there is 12v on either side, or that there is 10,000v on either side because a power line fell on the car .

 

It doesn't tell you much in other words. Doesn't even tell you if the fuse is good because there might not be any voltage present - might as well be sticking the meter probes into your toes at that point.

 

You need to check for 12v between either side of the fuse and ground - generally the Subaru fuse box lids will have an arrow indicating which side is "batt" and which side is "load". That tells you which side of the fuse is supposed to have power. You can check that side (through the top of the fuse - the leads are exposed on the top of blade-style fuses so you don't have to remove them) with the meter's red probe and the black probe on a good body ground point. If you have voltage potential you will get a 12v reading. That tells you the supply TO the fuse is good. Move the red probe to the "load" side of the fuse and if you still have the same reading that tells you the fuse itself is good.

 

Then you need to see if there is problem with the lead running from the fuse to the fan. Check from each leg of the fan connector and the battery ground. You should get 12v on one of the these pins. That indicates that you have power at the fan.

 

Do those tests and tell us what you find. I doubt you have power at the fan if jumping the temp switch didn't kick it on so no need to get into further detail till you actually perform these tests.

 

GD

[Mantis_Toboggan]

As a quick and dirty mnemonic, think of electrical components as dams on a river, and the water as electricity. Using a multimeter on both sides of the device measures how high the dam is. If the dam is broken, it will read nothing. At that point, you either have a free-flowing river or a dry river bed.

 

I'll be leaving the country in a few hours, so I'll likely not be able to follow your progress for a few weeks.

Good luck on your circuit!

[idosubaru]

thanks. in theory i know a ton.....i've had electrical engineering classes and labsf. V=IR P=IR^2...gaussian surfaces, BLEH. practically speaking i might just stick the probes in my toes to see what happens. GD you silly rabbit.

 

thanks, for the tips i can do that.

[GeneralDisorder]

thanks. in theory i know a ton.....i've had electrical engineering classes and labsf. V=IR P=IR^2...gaussian surfaces, BLEH. practically speaking i might just stick the probes in my toes to see what happens. GD you silly rabbit.

 

thanks, for the tips i can do that.

 

Hehe - yeah there's a big difference between theory and practice if you aren't familar with how the "industry" likes to build things. It's one thing to understand electrons and current and resistance, etc. It's quite another to troubleshoot something that's broken - be it electrical or mechanical - I have found that very often the engineers that design this stuff are made to scratch their head and look like a deer in the headlights when it doesn't work - and they know little about actually taking readings with a DMM or where to start looking for a problem. Some do - but others are made to look like fools if they have to do anything that doesn't involve drawing lines and selecting icons with their index finger.

 

And even when they do understand - it still takes people like myself who are "down in the trenches" to bring them the faulty part and tell them how badly they designed it and why . And sometimes it's followed closely by an "and I fixed it for you - add this to the design"

 

GD

[idosubaru]

i like the dam analogy, that's a good one.

 

yes engineers have earned their stereotypes.