West-se

My fan stopped working and I've started trouble shooting why. It was working fine for awhile but has stopped. I've replaced the transistor which controls it and I've replaced the relay. On the stim it works fine, the fan output light comes on (in megatune) and it trips the relay as expected. Once back in the car when I set the points at which fan comes on nothing happens, the coolant temp passes the set point and nothing , the fan output light doesn't even come on. I figured I ask here before heading over to msextra forum. The odd thing is that it works on the bench with the stim but nothing when in the car, if I ground the lead that goes to the relay on the chassis or the ms ground it activates the fan but when connected to the transistor connected to JS0 I get nothing. Its making me wonder if I've got another problem somewhere else on the board.

SCCA RX7 RACER

Hello Sean

In my business I deal with all types of electrical problems on the equipment I sell. Even a new part can be faulty right out of the box. I know of your work experience and your knowledge of these Mega squirt boards is very strong. The one thing that pops out at me was having the relay (Fan Relay) operate from your simulator but not the Mega Squirt board. In the past I have had relays new or used on the coil side not creating the magnetic field to pull the contacts together. Poor voltage to the coil or the wiring or the JS0 is not creating the same quality of ground as if you did it in your tests. It sounds to simple but I found simple some times trick me in this way. We over look the obvious.

Have a good Xmas

West-se

Thanks Kim, the odd part of this problem is that once in the car, megatune doesn't show that the fan is even turning on. I've tested the output js0 with a meter and it is working, ground when fan on, no ground when off.

renns

Do you have your coolant temp thermistor calibrated properly? Do you have the correct thermfactor.inc file in your mtCft folder? Sounds like a software/setup issue to me.

West-se

Correct me if I am wrong when you set the fan on temp to N and when megatune says that the sensor is reading N, should not ms then turn on the output for the fan? and the fan/water inj light should come on in megatune ? This works as I've described using the stimulator, but in the car it does not. Im on my 2nd transistor 2N2222A and my 2nd 30A relay. The relay works If I ground pin 86 to the chassis, but nothing if its connected to the circuit. I'm wondering if my circuit on the transistor is not creating enough ground ? Right now im using the ground on the proto area for the transistor, should I try changing to another ground ? not sure if it matters or not where I get ground just as long as its grounded....

renns

MegaTune doesn't know what temp the sensor is reading. It only knows the raw ADC value reported by the analog input connected to that sensor circuit. MegaTune uses the thermfactor.inc file to convert between the raw ADC value and degrees F. The data within the thermfactor.inc file is also embedded within MS, so if MS is programmed to turn on an output at 200 degF, it is able to do so. If there is a mis-match between the embedded version and the version on your tuning machine (desktop or laptop), you will see the symptoms you describe.

West-se

Ok, I understand let me double check my files.