Hi 'sweetsixteen' and 'Bergi',
Many thanks for your enthusiasm and the invitation.
I was referred to this forum by an electronics engineer who found the post from 'captainsaltry' and 'bluepanda' under the heading Power Steering Torque Sensor Info after I suggested I was going to scrap my Panda and go sulking in my hideout in Portugal in disgust after getting a £2,500 estimate from FIAT maindealer.
Analysis of vintage analogue power amplifier circuits with my very impressive 'nerd' friend was easy compared to dealing with the wall of fear and over dramatized
'we won't touch the sensor, only supply a complete column' attitude of Fiat garage.
This EPS thing is a much
overrated dragon and Perhaps with the help of the posts from 'captainsaltry' and the offered photos from 'bluepanda' we can slay it once and for all , at least for Fiat owners. Overcoming the 'Big Business' agenda of beating the crap out of its customers with technology is very do-able but it has to be done very carefully and the legal implications below should be noted.
I do strongly recommend reading the posts from 'captainsaltry' and 'bluepanda' under the heading ''Power Steering Torque Sensor Info'' in conjunction with anything I post. 'captainsaltry' has approached the task in the appropriate 'tech' way but a more 'anybody can do it' method is also valid here.
As mentioned above, there is much LEGAL history associated with EPS particularly from the USA. It was argued that stories of some very dangerous vehicle behaviour, when these EPS units malfunctioned suddenly, rendered the manufacturers liable and at least justified a re-call where manufacturers should correct the fault at their own expense. The up-shot is Big Business won as usual. They argued that the deterioration of the sensor is progressive and that in most cases of complaint, the drivers continued to use the vehicle long after the EPS warning light appeared and that the chance of the software failing catastrophically is about the same as a front tire blow-out and therefore within acceptable margins.
Personally, I used my Panda for around five weeks after the warning light came on and the signal from the TORQUE SENSOR did indeed deteriorate to the point where car was pulling hard to the left. A life that is dependent on a small cheap component fitted to a vehicle is a sad one.
The implication here is that, if you continue to drive a vehicle with the EPS warning light illuminated, you deserve what you get. I only try to give the flavour of this stuff here, the actual documentation is vast and you would die of boredom if you have not already.
A FEW OBSERVATIONS
I have actually dismantled the failed Torque Position Sensor removed from my 2005 Panda Dynamic 1.2 to see what all the fuss is about and to see if it could be repaired with a bit of cleaning or something. This component is NOT packed with complex circuits, chips, diodes, resitors or any digitally programmed 'heavy duty' technology. It is simply 14 very thin, concentric, electrically conductive, circular printed carbon tracks on one disc and 14 corresponding spring steel 'tongues', mounted at an angle relative to the disc they are mounted on, which are precisely positioned to make contact with their associated tracks on the lower disc. THAT'S IT.
Imagine 14 1965 Morris 1000 horn-push assemblies, miniaturized. This is not TECHNO TECHNO TECHNO. No Harry Potter, Camelot etc. more Blair Witch than anything else. The carbon tracks do present a differing electrical resistance depending on length. It is this difference in resistance which is utilized to send an electrical, as opposed to a digital signal or, indication of which direction the car driver is turning the wheel..
The spring steel 'tongues' which make electrical contact with the carbon tracks are very thin and delicate and each is further divided into 5 even smaller 'tongues' forming a structure similar to a brush. The contact ends of these 'brushes' are formed into a semi-circle, ( a bit like the 'ticks' in a box ticking tax form but with the pointy bit rounded off) since they stay in contact with the carbon track for 180 Degrees+ in both directions and would slide in one direction and dig into the carbon track in the other direction if they were not formed thus.
After a few thousand car park maneuvers etc. these contact points wear through the contact area, the turned up end of the 'foot' part of the brush drops off and the then sharpened end of the spring steel 'tongue' digs into the carbon track in one direction and starts to destroy the carbon track. Furthermore, the now detached turn-ups are floating around and interfering with the function of the remaining tracks.
This 'signal', no matter how corrupted or aberrant, is nevertheless transmitted to the 'brain' (( The steering column has it's own dedicated logic processor or controller)) in the steering column. It increasingly desperately attempts to ignore the spurious elements of the signal fed to it from the ''FAWLTY '' Torque Position Sensor and act only on those voltages (signals) it has been programmed to respond to.
Eventually it all becomes too much for it and it says''f--- this'' and sends out a request to the main ECU to flash or display the power steering warning light but still continues to try to do it's job. Eventually it will say ''that's IT'' and sends a request to the main ECU, ''Please shut me down completely, I can't do this anymore'', '' Get me 'outa' here before I catch fire'' etc. and then there is no power steering assistance at all.
All electronic data processing creates heat in the device doing the processing, deciding what is spurious or unreadable corrupted data is still 'processing'. The worse the sensors innards get scrambled, the more 'crap' it sends out, the chip gets hot trying to operate outside its' envelope and begins to output bad data. Turn off ignition for a minute or two, chip cools down and will function again until it cooks again. I think you all know the rest of the scenario.
There will, of course, be many variations of the above all with much the same result ERR ERR etc. OFF.
Now for the TRULY frightening
Limited but not that limited knowledge of production costing, injection moulding robotic assembly, final testing (Quality control ) and labour costs suggests the sensor is more than likely produced for under a fiver, possibly close to£2. Manual assembly and testing of the final product I can see could be done in less than two minutes.
The rest is Business.
My own experience of this steering malfunction manifested itself as a slight off-centre, i.e. a constant slightly heavy right hand was required to maintain a straight ahead condition. Eventually this malfunction was augmented with an occasional buzzing judder and an even heavier right hand, again, to maintain a straight ahead course on a motorway for example. Carry on driving, 'gotta pay the bank back, the TV license, the rates, blah....blah... blah you all know the story, and the vibrating is constant and 'The Jolly Green Giant wants to turn left'. Seventy miles later ( one commute ) ''Good grief, this thing is possessed. It's trying to kill me'' Pulling hard to the left, constant loud juddering followed by periods of no ASSISTANCE to the steering. It's like a workout in the gym steering this thing with no assistance. No self centering. Five minutes ignition off, thrash Panda with branch of eucalyptus, ignition back on, power steering back on but same conditions as above. Repeat, repeat, total surrender, must press on, vast amount of worse things to deal with. Pulled the fuse on the EPS, 475 miles of upper torso workout later getting stronger and looking good in the mirror, a bit like Arnie in The Terminator, too bad about the legs though.
Took Panda to expensive EXORCIST (Fiat dealer). Diagnosis: 'Possessed' Torque Position Steering Sensor. Remedy: ''loads a money mate, can't really
exorcise these things, you gotta buy a whole new steering column, loads a money mate, 'ave a look at our selection of previously owned vehicles, they're loads a money an all ..........mate. ''
Up until the point of £45 Fiat diagnosis I was convinced a relay was at fault because the judder was reminiscent of the frequency that a relay will open and close the electric circuit it is meant to control when it starts to 'chatter'. This is a condition which occurs when the voltage to the electromagnet assembly ( inside the relay ) is fluctuating. This fluctuation can be caused by various circuit abnormalities too complex for this posting but one which the average home mechanic can deal with is 'connection oxidation '. REMEDY: pull spade connections apart several times to clear the contact surfaces of this crusty stuff. Oxidation raises the resistance of the connection and therefore drops the voltage. Low voltage can also be caused by a crap battery, crap Batt.
and oxidation equals
demonically possessed wiring loom.
I mention relays here because I have read a posting on this forum from somebody who took one of the relays apart and rebuilt it believing that these are no longer available.
Can't be certain without wiring diagram but it looks like the two circuit board mounted relays on the end of the EPS motor simply reverse the DC supply to the DC motor and therefore it's direction of rotation. One relay activates to: assist turn right, other relay activates to: assist turn left.
It should be noted that most commercially viable relays will have a finite number of times they can reliably activate ( open and close contacts - make and break a circuit). Under 'chatter' condition your relay is using up its' life at several hundred times the rate it is designed for. Big DC spark at contact points burns and sometimes welds the points together also.
Going by the posts under ''Power Steering Torque Sensor Info'' in this forum, I think I would agree that 99% of EPS failures are probably caused by deterioration of the 'SENSOR' because the rest of the system is almost bullet proof with the exception of the two or three examples above, dodgy battery being responsible for most of the remaining 1%.
IF we accept the above is true, why give FIAT dealer £45 to tell you the sensor is defective?. Use the £45 toward a new sensor, why feed the Vampire.
I have laid out my experiences of the sensor failure so any reader can compare their own notes against them and decide for themselves if it is worth taking a £70 risk and trying to fit the thing.
My decision to try replacing the sensor was easy, I don't have a spare £2,000 just lying around for FIAT to Hoover up, or to buy another car. Very much a forced gamble and had to be done quickly so some errors were made and I will be as precise as I can in my next posting, on how to avoid them altogether.
I'd like to express my gratitude to 'portland_bill' for his assistance in getting started rectifying one of these errors, specifically the damage to the 'strip circuit' connection to the horn/air bag in the steering wheel boss. This is sometimes referred to as the ''clock spring'' and is more a description of what it looks like and the fact that it is secured at both ends. This error is
easily avoided . Details in next post with step by step procedure.
Please make an effort to watch the 'Dormans video' on You Tube relating to replacing the steering sensor. This will give you a good idea of how easy it is to replace this component but bear in mind that if you follow the guide in
MY post, you will be replacing the sensor without removing the entire steering column, only the top half. By doing the fix with the lower half of the column still connected to the steering rack you avoid all the re-synchronizing problems many have experienced.
Please also read posts from 'Bluepanda' relating to replacing the sensor.
Let's get smart and get lucky.
Regards
Satyr Icon