Hi there,

Finally got a replacement thermo fan for my 3.5 Verada. Old fan had low speed burnt out. Installed new fan, and low speed working. But now, when engine warms up, low speed kicks in but does not switch off (yes the A/C is off) - even when driving!! This would explain why the old fan burnt out.

Replaced the relay in case it was sticking - but did not solve the problem.

Could it be a faulty thermo switch/sensor incorrectly reading a higher temp than it actually is therefore leaving the fan running when it is not necessary?

Are the thermo sensors the same for 3L and 3.5L?

thanks

Louis K

swap the relays around see if it changes

Check the temp. sender switch. If it's not sending a proper signal, the ECU will keep the fan on all of the time.

Hi Magna LE

Do you mean the sender for the Temp Gauge or the Thermo Sensor that controls the fan? How do you check if the Sender is faulty?

Relays already checked, but that does not seem to be the problem.

You need to check both. If either goes into an open circuit state (ie; broken wire, broken switch, etc.), then the ECU will keep BOTH thermo fans on.

If it's only the main fan then it's either the thermo fan switch or a problem with the cooling system itself (I assume you've already checked the coolant level, cooling system pressure, etc.). Also, for 3rd gens, if you're doing less than about 30km/h (I'm not sure of the exact speed...ask a Mitsubishi service guy), then the ECU will keep the thermo fan on.

The easiest way to check is to just start up your car and let it warm up until the normal thermo fan cycle kicks in. If the fan doesn't shut off after about a minute, rev the car to about 2000 RPM for about 15 seconds and then let it idle again. The fan should shut off within a minute or so of doing that. If it doesn't, then there's something wrong.

I'd suggest to just book it in at a Mitsibishi dealer and ask them to check the thermo fan cylce ('cause they can just hook it up to the computer and get a read out of the exact temps. that the fan(s) are cutting in and out at).

Sorry...I know that's not much help to you.

swap the relays around see if it changes

Ummm she replaced the relay?????

Check your thermo switch.

I have had another TF doing this where the ECU was sending the signal. The car had previously been in a minor accident, the panel beater had been rough with the wiring and damaged the loom, the wire from the thermo switch was sending a false signal to the ECU and then the ECU decided to run the fan.

Not saying this is your problem but to test, disconnect the thermo switch and see if the fan stops, if it does, get a second hand swithc, they are not hard to find and then if still problem, your wiring or ecu is to blame

i know it sounds silly.. but try changing the radiator cap! i on 2 occasions had the problem of the fan not cutting out on a 3rd gen magna.. and with a quick check using the MUTT, i found the coolant temp reading was out.. causing the fan not to cut out! give it a shot and good luck!

p.s: oh, get a genuine cap, that way, u know the pressures are correct.. cheap too, not even 20 bucks!

Even cheaper if you buy them from me for $10 bucks genuine lol

The car start up normally but once the fan kicks in, it keeps on running. Once the fan is on, it does not stop until I turn off the car and leave it to cool down. The strang thing is that after the car cooled, restart the car and the fan remain off until the engine heat up again.

When this happened, I've taken the car around the block several time but when I parked to check if the fan was off, but it was still running.

Points to note are:

1. Fan is not running when the engine is cold, it only turns on when the car warmed up.
2. When I turn off the engine and leave it to cool down then restart the engine, the fan remain off until the engine warmed up again. Once it is on, it does not turn off like other car does until you've turned off the ignition.

Anyone have any idea ???

How did you fix it

Hi Tomking

Don't have the car anymore, but I have a feeling it might have a sticky thermostat.
When the fan is running, feel how hot the top radiator hose is near the thermo housing. Could be faulty thermostat which means that the water is hot inside the thermo housing next to thermo sensor (setting the fan off), but as the thermostat is not opening correctly, water is not flowing efficiently in the hose, so the hose is actually cooler than the housing.

Try changing the relay for it in the main fuse/relay box in the engine bay.

Try changing the relay for it in the main fuse/relay box in the engine bay.

yeah already tried that but it didn't help. the temperature gate is stabled at the middle, might try to replace the thermal stat. Any idea how much it cost ?

Hi, new gen Thermo stat is around $40, plus coolant.

Use a genuine thermostat, the saving is not huge with a non-gen.

LouisK

Hmm i think mine has these symptoms too will have to check it out....

Has anybody got any ideas on the fan control speeds?

Mine may well have the 30km/hr fan control but i haven't noticed this on other 3rd gens in the family...

Hi, new gen Thermo stat is around $40, plus coolant.

Use a genuine thermostat, the saving is not huge with a non-gen.

LouisK

Genuines are $27 (MD194988) - non genuines are over $100 (!) so yeah go genuine.

Hi there,



Are the thermo sensors the same for 3L and 3.5L?

thanks

Louis K

Yep - same from TE to TJ at least - MD177572-Sensor Unit-Water Temp - $102.00. I'm betting your sensor is stuffed given all the above. This is the larger one fitted near where the top radiator hose goes into the engine. The smaller one next to it is for the temp gauge in the dash.

OK just done a quick check...

My Rad fan low speed comes on and pretty much stays on at idle....

But if i DO give it a slight rev say 1500 to 2000rpm it WILL turn off in a short time..

If i disconnect the coolant temp sensor both fans go to high speed and i get a check engine light...thats good ...

Looking more like a thermostat issue...certainly cheaper than the coolant temp sensor...!!

But alas this could be what later 3rd Gens to ???

Any body with a late 3rd gen confirm this?

I now have this exact problem with my TJ, did anyone work out what it was?

Read posts 5 & 6.

Check your thermo switch.
Check your thermostat.
Check your wiring.

Read posts 5 & 6.

Check your thermo switch.
Check your thermostat.
Check your wiring.


Yes.. However I was hoping someone who was having these problems in this thread would be able to give any solutions (ie which problem is was)...

My fan comes on after about 5mins, stays on, all this time the top hose is red hot, the bottom is cool, but the temp gauge is normal (just before half).. so before i start taking things to bits...

I have a question, under normal circumstances, should the thermostat be opening fully, before the need for the thermo fan to come on?

That sounds like a thermostat fault to me.

I have a question, under normal circumstances, should the thermostat be opening fully, before the need for the thermo fan to come on?

:bump:

Someone?

Yes providing the A/C is switched off...

i think the question is : does anyones fan cycle when hot?

all the g3 magnas ive seen to date run the fans continuously at idle

i was gonna try bridging the condensor fan relay diode behind the dashboard to get both fans running and see if it drags the temp down and causes the fans to cycle

maybe i should consult one of the techs at mitsubishi about the fan control system

I understand at idle, but this is after idle, it just stays on, period

I solved the problem, changed the thermostat...

Now, what was happening is that the existing themostat was opening, but too late (93C) instead of 88C, so the fan was coming on and being forced to stay on due to the restricted flow of water from the radiator (thermo wasnt opening fully either)..

One other thing to note is that I bought a DAYCO thermostat, supposedly Part #DT56D, then when I got to Repco they said it was a discontinued line and DT56E replaced it, however that one has a opening temp of 77C, much lower than it should be, that one was $46. I then went and bought the genuine one for $68 which did open at the right temp (by testing it on the stove in a saucepan).. Hopefully this will be useful for anyone in the future.

Now the bottom rad hose gets nice and warm a long time before the thermo fan comes on, and the thermo fan does cycle. :thumbsup: :thumbsup: