My brother just bought a tokunbo Acura MDX 2008,3.7l engine capacity from Canada. Expectedly it came with two fans. One for the engine/radiator and the other for the AC. I noticed that when the AC is not on,the engine fan will pick as soon as the engine gets warm,but when you turn on the AC,the AC fan comes on while the engine fan goes idle. The AC fan is controlled by the thermostat as such it comes on and off. But the engine fan rarely works same time with the AC fan which most times results in the rising of the temperature guage above the middle line. A rewire was contacted who installed a relay that now enables the engine fan to work whenever the engine is turned on, while the AC is still working normally as installed from the factory. Note that the temperature has remained normal since then. Experts in the house please I want to know if we have done the right thing.

chuckynath:
My brother just bought a tokunbo Acura MDX 2008,3.7l engine capacity from Canada. Expectedly it came with two fans. One for the engine/radiator and the other for the AC. I noticed that when the AC is not on,the engine fan will pick as soon as the engine gets warm,but when you turn on the AC,the AC fan comes on while the engine fan goes idle. The AC fan is controlled by the thermostat as such it comes on and off. But the engine fan rarely works same time with the AC fan which most times results in the rising of the temperature guage above the middle line. A rewire was contacted who installed a relay that now enables the engine fan to work whenever the engine is turned on, while the AC is still working normally as installed from the factory. Note that the temperature has remained normal since then. Experts in the house please I want to know if we have done the right thing.

That rewire has jst ran your engine fan direct which will eventually shorten the lifespan of your fan and even that of your engine cos your engine temp will never achieve optimum temperature .
The correct strategy for your 2 fan operation is automatically dictated by the engine computer (ecu ) and the two fan are supposed to turn on together at same time and and run together and the period that the two fan should turn on are
1. When your engine temperature get to high threshold ie .97 degree
2. When ac are turned on
And anything outside these conditions above ,the fans should be turned off.

autologic:

That rewire has jst ran your engine fan direct which will eventually shorten the lifespan of your fan and even that of your engine cos your engine temp will never achieve optimum temperature .
The correct strategy for your 2 fan operation is automatically dictated by the engine computer (ecu ) and the two fan are supposed to turn on together at same time and and run together and the period that the two fan should turn on are
1. When your engine temperature get to high threshold ie .97 degree
2. When ac are turned on
And anything outside these conditions above ,the fans should be turned off.

.

Thank you for your valid and informed points. However,in course of trying to have the engine achieve optimum temperature, wudnt that lead to over heating thereby affecting the engine,given that the two fans weren't working the same time and the temperate region we reside in?
Yea the life span of the fan obviously will be shortened,but wdnt that be better than having the engine guage rising above normal?
Thirdly, inability of the engine to attain optimum temperature and the engine exceeding optimum temperature,which of the two posses a higher risk to the engine?
Your informed inputs will always be appreciated

chuckynath:
.

Thank you for your valid and informed points. However,in course of trying to have the engine achieve optimum temperature, wudnt that lead to over heating thereby affecting the engine,given that the two fans weren't working the same time and the temperate region we reside in?
Yea the life span of the fan obviously will be shortened,but wdnt that be better than having the engine guage rising above normal?
Thirdly, inability of the engine to attain optimum temperature and the engine exceeding optimum temperature,which of the two posses a higher risk to the engine?
Your informed inputs will always be appreciated

I think this kind of discussion has been overstretched on nairaland and u need to search for appropriate thread to get your self informed but I will still give you some eye opener .
The fan kick- on strategy described above is the full proof design of the manufacturer of your car where millions of dollars has been expended in R& D and this same model used regardless of location and even for areas like Arizona ,Texas and Dubai that even hotter than Nigerian in term of climatic condition, and I am sure you don't want to say you know more than the maker of the car .
Also ,coupled with my own theoretical and practical knowledge and experience of donkey year of auto engineering practice, having seen and attended to thousand of case studies and still counting , with access to latest training abroad ,I am yet to see any manufacturer ,or any scientific study that will ever encourage maintaining your engine temp low relatively to optimum middle mark or above cos it will destroy your engine and will also result to environmental emissions hazard(naija peeps don't even care about that ).,
unfortunately nigeria mecho are the only people perpetrating this evil practice and the reason they are still in business of destroying cars is because you people keep patronising them which is why naija engine dont last and we are enriching the part sellers.
Below picture depict a case study of a Nissan 2016 that was towed to our shop with complaint of inability to start (severely abused from previous tech )untill we discovered that engine is already choked with sludge which eventually ruin the engine (I will still do a detail troubleshooting analysis of case study of this particular vehicle in subsequent thread ) .Just another case of typical naija lackadaisical to their vehicle maintanance by running the fan direct .