mackncheese Posted March 8, 2016 Share Posted March 8, 2016 My 05 Granite CV 713's (1M2AG10C75M026820) cooling fan is allowing the truck to get much hotter before coming on and then will run for a second and cut right off and back on. Then it will run like it normally does and stay on for a couple of minutes. I have 2 water temp gauges in the truck the factory one in the dash and an aftermarket autometer. The autometer gauge reads about 20F hotter than the factory gauge, and the fan would come on when the autometer gauge reads 210F now it will get up to 230F before the fan comes on. The factory gauge shows about 200F before the fan comes on. We replaced the fan switch and this is still happening. Can you all tell me what the problem is? Thanks for your time. The engine is ASET AI 460 hp. Quote Link to comment https://www.bigmacktrucks.com/topic/44264-05-granite-fan-acting-wierd/ Share on other sites More sharing options...
wheeler73 Posted March 10, 2016 Share Posted March 10, 2016 If the computer is reading the same as your factory gauge you may havea bad coolant temp sensor that is reading lower than actual temp. Also there could be high resistance in the wiring to the sensor and possibly a defective eecu. Most common is the coolant temp sensor. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/44264-05-granite-fan-acting-wierd/#findComment-327081 Share on other sites More sharing options...
Challenger Posted March 11, 2016 Share Posted March 11, 2016 The engine should have 2 coolant temp sensors. One for the gauge and one for VMAC III. They are both mounted onto the water manifold. The gauge sensor is the "fatter" sensor sticking out of the side of the water manifold. The VMAC III sensor is the smaller sensor sticking out of the back of the manifold. Its the VMAC sensor that operates the fan. Since the fan and temp gauge work off of different sensors, when one goes bad they wont be in line with eachother. Quote Link to comment https://www.bigmacktrucks.com/topic/44264-05-granite-fan-acting-wierd/#findComment-327219 Share on other sites More sharing options...
mackncheese Posted March 12, 2016 Author Share Posted March 12, 2016 Thank you both for the feedback. Called the service manager at the Mack dealer and he said his first guess was bad thermostats. Replaced both of them and drove the truck. At first I thought all was well. The fan came on and bought the temp down. But it only came on once, thereafter the aftermarket mechanical gauge get up to 240 while the factory gauge never got to 200. Oil temp got close to 250. Also saw the factory gauge go down to 110 or so and then rise to 190 all in about 3-5 seconds. No lightning bolt light on and no de rate. Mack dealer is an hour and a half away and can't get to me till late next week and I need the truck. Should I buy sensors and replace? Once again thanks for your time. Quote Link to comment https://www.bigmacktrucks.com/topic/44264-05-granite-fan-acting-wierd/#findComment-327246 Share on other sites More sharing options...
Challenger Posted March 12, 2016 Share Posted March 12, 2016 The temp sensor and gauge have nothing to do with the fan engagement. Its strictly an instrument gauge. This should be the fat sensor sticking out of the side of the water manifold. How long has this gauge not read properly? The VMAC sensor runs the engine fan, this is the sensor that tells the EECU how hot the engine is running. If its bad and jumping around in readings the fan will follow. This is the smaller sensor sticking out of the back of the water manifold. If your autometer reads steady and doesnt jump around, replace the VMAC temp sensor sticking out of the back of the water manifold. I replace this sensor with out draining the coolant. Remember this will not correct your original gauge reading, but hopefully repair the fan and running hot problem. Good luck Quote Link to comment https://www.bigmacktrucks.com/topic/44264-05-granite-fan-acting-wierd/#findComment-327344 Share on other sites More sharing options...
mackncheese Posted March 25, 2016 Author Share Posted March 25, 2016 Long story short. Took truck to the dealer and they changed the probe on the factory temp gauge and all seems well. Also had them install a switch on the dash that will manually turn the fan on. Quote Link to comment https://www.bigmacktrucks.com/topic/44264-05-granite-fan-acting-wierd/#findComment-328369 Share on other sites More sharing options...
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