MS3X Fan Control Issue

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alex240
Helpful MS/Extra'er
Posts: 36
Joined: Tue Nov 04, 2014 6:39 pm

MS3X Fan Control Issue

Post by alex240 »

Hello All,
I have had a weird issue pop up recently on my MS3X install in my 240sx with a ford 5.0L engine. This setup has been in the car for two years with no issues until now. The fan control has begun clicking the relay on and off several times a second and never actually turns the fans on. When the engine is off it works fine and I can turn it on using test mode and the fans run fine (or if the coolant temp is above the fan on threshold and I turn off the engine the fans will then turn on).
I have swapped the relay with no change.

I have attached a datalog of the car idling while it was happening as well as the tune. Here is a video as well: https://drive.google.com/file/d/1W6Q8rk ... sp=sharing

Any Ideas would be greatly appreciated. I have had to wire my fans to a switch on the dash but it sucks having to remember to turn it on....then have it overcool the engine and have to turn them off, etc. etc.
Attachments
2018-01-10_23.19.27.msl
Datalog
(1.06 MiB) Downloaded 25 times
2018-01-11_00.48.48.msq
Tune
(272.96 KiB) Downloaded 20 times
SwedCharger-67
Experienced MS/Extra'er
Posts: 264
Joined: Sun Dec 23, 2012 2:20 pm
Location: Nordmaling, Sweden

Re: MS3X Fan Control Issue

Post by SwedCharger-67 »

Your battery voltage is very low. Could that be the simple reason?

When the fan kicks in, your battery voltage drops even further, could cause your engine temp reading to be slightly lower, the CPU switches off the fan...voltage goes up again...switches fan on... :)
Martin, Sweden
Mopar 512 cui, 8.4 liters, high compression, fuel E85, full sequential control by MS3X, burning rubber just blipping the throttle... :D
alex240
Helpful MS/Extra'er
Posts: 36
Joined: Tue Nov 04, 2014 6:39 pm

Re: MS3X Fan Control Issue

Post by alex240 »

The battery voltage in the megasquirt has always shown 2v-3v low, ever since I built it so I usually ignore it (probably not the proper way to go about it :? ). But your right it is exceptionally low I will charge the battery and hope its as simple as that!
alex240
Helpful MS/Extra'er
Posts: 36
Joined: Tue Nov 04, 2014 6:39 pm

Re: MS3X Fan Control Issue

Post by alex240 »

I charged the battery and tried again today. No change, the fan output still is intermittent. I also checked the voltage at the battery (engine running) and it is 14.5V while the mega squirt shows ~10.9V.........

Testing on bench with jimstim providing power from wall outlet-
Ground pin to left leg of U5 on MS3 board: 10.56V
Jimstim output to MS3: 11.31V
voltage shown in tunerstudio: 10.9V
So 0.75V drop through the megasquirt.

Testing harness in car, engine off, mega squirt disconnected-
Voltage at MS3 Connector (harness side): 11.68V
Voltage at battery terminals: 12.13V
So 0.45V drop through the wiring harness.

Do I need to look into wiring issues?

I also reflashed the firmware with no change.

I'm at a loss, any ideas?
alex240
Helpful MS/Extra'er
Posts: 36
Joined: Tue Nov 04, 2014 6:39 pm

Re: MS3X Fan Control Issue

Post by alex240 »

Problem solved....not sure why but the "allow fan while engine is off?" option was causing the fan output issues. I have turned it off and everything runs as it should.
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