Cooling fan always on? Wtf?
 

Hey guys!

I've had the strangest things happen to my car since I installed the Megasquirt. For starters, when I turned on the car, the radiator fan would turn on automatically. This didn't really bother me, as I just figured the MS1 probably turned it on all the time...

But now I've just arrived home, turned off the car, and the fan stayed on????

I have no idea what's happening... What could cause the fan to stay on all the time? Could it be a faulty relay? I doubt it could be the Megasquirt, because that is turned off with the ignition I reckon. And I don't think the car has any thermovalve that could cause the fan to keep running. It just doesn't shut off!

What can I do to check where the problem is coming from?

fix your megasquirt settings...

Does the Megasquirt even control it? From what I can tell on the service manual, the only things controlling the fan are a pure electrical circuit comprised of a thermoswitch mounted above the thermostat, and a relay. The thermoswitch-to-relay circuit is ignition triggered, and the relay-to-fan circuit is connected to the battery directly. And that's all there is to it, for pre-93 cars, no?

The problem seems to have vanished now though. I replugged everything and it's working fine again. I think the relay might have stuck closed?

no. i think your ms was keeping it on for some reason.

who built your ms?

You did! XD

Also, if that were the case, the Megasquirt would de-power the fan when you turn off the ignition, since the MS itself relies on ignition power. But the fan just keeps on running after I turn the car off.

then check the settings on the outputs. most likely wled.

But don't the outputs all go to zero when you turn the car off? That automatically excludes the MS as a cause.

oh... yeah. didnt see that. It will run it when the motor is off and key on....but i think that's just an ms3 option.

if it was running with car off and key out of ignition, it was probably a stuck fan relay.

Stuck relay checks out!

The car did it again a few hours ago, only it didn't stop. I took off the battery again, and when the car was cold and I connected the battery, it was still at it. So I thought I'd give a beating to the relay, and what do you know, the fan stopped! :)

So now I have to just gently tap the relay to get it to unstuck every time I drive the car. Oh well. I need a new relay, and no Mazda dealers around.

If you have any junkyards around you that relay is common in the 626, MPV, MX3, and protege.

Grab a handful for cheap

Nope, no dealers and no junkyards :(

And those cars are all pretty rare... I doubt I'd find them in a junkyard. Gotta go by a Mazda dealer tomorrow and do a price enquiry.

Get on over to MX5Nutz, I'm sure one of the breakers like JunkYardDog would be willing to post one over to you.

Rockauto has em for pretty cheap I think. Did you have to beat on the on in the box or the one by the intake/throttle body. If its the one in the box I think they are only 10-20 dollars shipped.

Hey guys!

So eventually my relay burned out and got stuck on open, and I was left fan-less :(

I replaced the relay with a new one, and all was fine again!

However, after only two days, the new relay got stuck closed again???? I'm pretty sure it is overheating from the fan being always on.

Brain, does the 9093 MS1 you built control the fan in any way? Because mine just seems to never turn off and I honestly don't know what to do now :(

yes. always build it in. but your thermoswitch could override it... check the MS settings.

I have given a quick look earlier today on my MS configuration and didn't find where I can control the outputs... Where is it? This must seem like a really newbie question to be fair, but since I was given this Megasquirt unit from a car that had undergone extensive modifications, many things had to be fixed by hand and I might have overlooked that one...

EDIT: In fact, I had already checked the settings before, on the Outputs tab of Tunerstudio (I reckon it must be using the JS3 output, right?) and all checks out. Does this mean I have a faulty thermoswitch? And why didn't it happen before with the OEM ECU?

As I expected, I turned on the ignition, fan started revving, then I unplugged the thermoswitch, see if that killed it...

... It didn't!!!

It was still running with the thermoswitch off. I guess that rules out any problems with the thermoswitch. What am I missing? Which output is programmed for the fan control, Brain?

post your msq

Crap. I don't have the latest version here. But this should be fine considering the problem was already happening back then, and all I changed since were VE tables and accel enrichment...

(Using hr10g for all that matters!)

Under basic settings > codebase and outputs, change LED18 from warmup to output 4.

then go to more settings > shift light | fans | output 3 4, under OUTPUT 4, change Use above source or FAN control to Fan control.

on the bottom used like fan on 200 and fan off 190.

burn all changes, power cycle. lmk.

Thanks Brain, will try that tomorrow and let you know how it fares ;)

So the fan should be setup using output 4 I assume? And not JS3? I was using the settings over from the DIYPNP old MS1 90-93 files as reference for those.

I doubt I wwould havve used js3. I don't think I could even.

By the way, out of sheer curiosity... Does the ECU supply 12V on that line for the relay, or does it just ground the line from the relay? I suppose the thermoswitch being a one wire only probably grounds the wire. Didn't test it.

Just a ground.

Brain, I tested just like you said, and it didn't work... Even though I set everything for outpu 4 (LED18 to Output4, Fan Control in the other panel, and set the temperatures roughly to what you said) but the fan kept on running. I was able to observe that, with LED18 set to Warmup (like it was) the Output4 gave an ON signal on Megatune's dashboard, and with it set to Output4, the Output4 gave an OFF signal. Regardless, the fan kept on running.

Also I noticed it only runs IF the engine is running. I thought it did on ignition, but nope, it's only with the engine revving. On ignition, the fan stays off.

Also, while searching the internet regarding this problem, I found out the previous owner of this ECU was having the same problem on his car, systematically burning out the relay due to over-usage.

Could it be that something inside the ECU is messed up? :(

Should I try and see if it works properly using JS0/X2?

Switched LED18 back to Warmup, and X2/JS0 to Fan Control on the outputs tab.

All fine and dandy :)

Thanks a lot for the help guys!

oh okay great!

This board is modded with VICS, Knock and WB inputs from what the previous owner told me :)

Okay so I'm back with NEW problems regarding this...

After I set the X2/JS0 to Fan Output like I said before, it all worked fine until recently. A new relay got stuck AGAIN! Only this time it was clicking while the car was cold.

I checked the relay wires with a multimeter. Between the main tabs, there's a differential of 12V which, when shunted, turns on the fan. That checks out.

I then checked the relay activation line. It measures a despisable amount of voltage when ignition is on (< 0.05V ), it measures a variable amount of voltage with the engine ON, and when the Fan is finally at the set temperature, it shows 14V as it should.

Now the odd thing is... The values it shows on the voltmeter with the engine running while below fan threshold are odd. They vary between 1-2V on the display, but from the relay clicks I figured the relay is momentarily activated at the same rate as the engine turns. It is as if there was an impulse signal to the relay when the fan is below threshold but the engine is running.

Could this be caused by a bad earth somewhere, a misconfiguration in my MS, or should I be looking into damage inside the MS itself?

Any help would be appreciated as this almost cost me my engine a few days ago when the car overheated badly because of this...

Could it be that, because the fan wasn't meant to be controlled by the ECU, when both the ECU and thermoswitch activate, the fan shuts off? I dunno, I'm completely lost here. I've tried everything I could think of!

no, both just pull the relay to ground, they can work in conjunction.

Radiator Fan Running with ignition off
 

My 91 Miata continues to drain the battery during the night sitting in my garage with the ignition off. I changed out the relay that I thought was the issue and changed the battery as the old one was weak. I walked out a week later to find the Miata fan running full blast with the ignition off. Could the temperature sensor cause this issue with the ignition turned off or does anyone have any other ideas? thanks