Power steering worked perfectly after chainging Mosfets in my car

Hi Friends well-come back.
Today again i am going to take you to the different story How i repaired my maruti Suzuki wagon-r vxi Model  power steering motor driver module.
Before the repair story  i would like to take you story how i faced the problem.When I brought my car I was not knowing about an electronic involvement even though i am a professional in electronic repair and servicing. Car technicians use to talk about ECM,Motor driver,EPS,Sensors,Electronic lock systems etc.
I am wondering what are all this terms?? How they employed in a mechanical automobile machine,Really as an electronic engineer its quite impressed me to find their functions.But i did not got chance to see all this until my car purchase.
Let me begin the story Once when i taken my car for riding its steering is very hard to turn right and left as compared before.I called my professional cab driver friend and asked regrading this.He advised me to lubricate the car in service center.





My maruti Suzuki wagon-r VXI



  As per my friends advice my car has gone to service center but  surprise to hear different story .They noticed an electronic module in my car gone bad and recommended new piece for the same called Electronic Power steering motor control module  EPS Which is  very high expensive. I finally realized the cost more than Rupees 9000/-.
 Generally as an electronic professionals we won't throw any defective electronic PCBs until unless finding route cause and its common things usually all electronic engineers will do.In my mind its very queries to see what is their inside this module??How it works ?? And why it is not repairable?? Finally  asked car service engineer for repair this module instead of purchasing new,but his replay is only solution is new replacement no repair solution.


Any how without power steering its UN-comfortable to ride my wagon-r and  made my mind to purchase new.Please go through the below image module for your reference.

Before buying such an expensive EPS need to know

what is their inside? Is it possible to repair myself?? How to save the money? Many questions.As a technician we need to think what are all the possibility for the break down to save the expensive cost .



EPS Module

Yes my assumption is correct .When I opened the chassis inside the components is nothing new to me its only H-Bridge /Driver section/Micro controller/Power supply section etc.Already we played a lot in my bench on this section on repairing kids  remote controller  car/Bike toys etc.



Typical Schematic Diagram






Connector pins DATA

How they Connected Motor V/S Sensor

Working Principles of Electronic Power steering

Electric power steering (EPS or EPAS) uses an electric motor to assist the driver of a vehicle. Sensors detect the position and torque of the steering column, and a computer module applies assistive torque via the motor, which connects to either the steering gear or steering column. This allows varying amounts of assistance to be applied depending on driving conditions. Engineers can therefore tailor steering-gear response to variable-rate and variable-damping suspension systems, optimizing ride, handling, and steering for each vehicle.[15] On Fiat group cars the amount of assistance can be regulated using a button named "CITY" that switches between two different assist curves, while most other EPS systems have variable assist. These give more assistance as the vehicle slows down, and less at faster speeds. In the event of component failure that fails to provide assistance, a mechanical linkage such as a rack and pinion serves as a back-up in a manner similar to that of hydraulic systems.

Electric systems have an advantage in fuel efficiency because there is no belt-driven hydraulic pump constantly running, whether assistance is required or not, and this is a major reason for their introduction. Another major advantage is the elimination of a belt-driven engine accessory, and several high-pressure hydraulic hoses between the hydraulic pump, mounted on the engine, and the steering gear, mounted on the chassis. This greatly simplifies manufacturing and maintenance. By incorporating electronic stability control electric power steering systems can instantly vary torque assist levels to aid the driver in corrective maneuvers.[16]
The first electric power steering system appeared on the Suzuki Cervo in 1988. Today a number of manufacturers use electric power steering. 

Machnical Assembly

Based upon the above theory I started to debug to find the solution to the break down.I am writing this article because many of our electronic repair technicians owning their vehicles may face such situations .Before starting i thoroughly inspected the EPS after opening the chassis I noticed the water has gone inside the module and H-Bridge mosfet has gone cracked physically it is clearly visible. Parallel i checked mosfet driver section and also found OK in my bench this is done only to improve my knowledge only.

I don't want to do experiment to my car because i cannot play with power steering mechenisum.I gone to maruthi suziki spare vendor to purchase the ECM. He doesn't have exact number and no warranty after purchase his cost is around 7800/- rupees.I don't want to take a chance for this equivalent number ECM.

My mind was thinking why i should not try my defective ECM for repair since it is having only mosfet damage.Checked the mosfet number IRFZ40.

Visited the electronic spare vendor asked IRFZ40. but this spare is not available tried in n number of shops but not available. Since it is an unique part adopted by Bosch company this ECM contains unique spare there availability is very very low.Electronic spare vendors always keeps the spare which is having fast movement common components.Because they always think commercially profit.

Even though as an electronic engineer i have not given up this task.Googled an internet checked the data sheets and varified the RDS,current and voltages ratings.Next gone to the same spare and asked equivalent but he charged rupees 200/- each.

IRFZ40. voltage rating is 50v & current rating is 50 amps.Equivalent NTB5412N voltage rating is 60v and current is 60 amps. In my career i repaired many inverter/UPS so I purchased n number of mosfets having voltage and current ratings more than 100v/100amper but their cost is not more than rupees 75/- each.

Ultimately i got doubt on this electronic shop vendor and i rejected this mosfet from him.Because for a simple experiment i cannot spend 800/- rupees 

Next i went to industrial electronic spare vendor and asked him to give any mosfet having its current and voltage rating more than 60volt and 60 ampere.He has given me two number type irfxxx and IRFyyy but selected NTB5412N and charged me only 35/- rupees each.Replaced in my defective ECM with this  NTB5412N  mosfet.Since this ECM is having N number of pins I don't have any testing jigs in my bench.

Ultimately with cheap cost of 140/-rupees in bench i made it ok now i want to test this working. And only solution is to connect in my car.I have taken it to car service center asked an electrician to re-connect and check for working.Once connected my power steering come into re-life again.I felt very happy to see this.Gone for trial riding working good even today its cool the same mosfet driving my power steering.

Yes i saved 9000/-rupees if you have a knowledge and time even you can do this.It's a worth of your education what you gained in your engineering.This above story is only about Wagon-r car.Think about higher end Car ECM .Once you become an expert on this you can earn like any thing.Ultimately car service person felt very happy & taken my contact for ECM Repair. 

   

Enjoying the  power steering  Riding

This is how i repaired my wagon-r Power steering module ECM.Hope you enjoyed reading this article.Let us meet in the next session with one more interesting story.

With Best Regards

Basavaraj:BM