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power steering switch

7K views 25 replies 12 participants last post by  fordboy98 
#1 ·
what do ya get when ya cross a broken power steering switch and a hot cat converter,,i tell ya's a lot of smelly smoke..

got home yesterday and there was smoke pouring out from under the bonnet(WTF)

had a look the damn switch shit itself,,bugger man..
 
#3 ·
I think those little switches along with the brake switch should be changed every 18 months :)
 
#4 ·
What exactly do the power steering pressure switches do? I mean, what is their purpose? You know there's no pressure when the steering becomes unbelievably heavy & you crash because you can't turn, but I just can't fathom how having the switch helps. Also, what sort of thread is it? You could just plug the hole it goes in.
 
#6 ·
no idea what it does but had it been designed by me, it would sense pressure drop and would dissengage a clutch on the pump so one can still turn the wheel when the pump dies.
 
#8 ·
we have an au2 that kept on eating the power steering switch and ford did'nt know what was goin on and we took it to them every 2-3 months cause it was leaking, so when the warranty ran out my dad got sick of changing it and just blocked the switch up and screwed it back on 1 year later no probs every thing works and no leaks.
 
#11 ·
I wouldn't be much use as a low level switch because it's on the power steering unit not the pump - but if it should have anything it should be a low level switch on the pump reservoir. Sounds to me like it's more an "ambulance at the bottom of a cliff" type system. My XF doesn't have one. And if it did I'd rip it out. I know the EA's had them and they were constant hassles.
 
#14 ·
basicly it is used to increase the speed of the engine when full lock is obtained by the driver,,for when one is parking the vehicle,,supposedly to stop it from stalling,,but until i got the ea i had never seen a switch on the power steering rack,,bloody friggin ford have to be bloody different don't they,,bloody so and so's
 
#20 ·
Hi guys,

The power steering pressure switch is designed to asssist the power steering effort at idle engine speeds. At idle, or when stationary (like parking manoeveurs), it detects an increase in hydraulic pressure when the steering wheel is turned. Normally, there is little pressure in the power steering system and only increases (and very rapidly) when the wheel is turned to steer the car. When the switch detects the increase in pressure, it signals the ECU to slightly increase the engine idle speed to compensate for the load imposed on the engine by the PS pump, thus ensuring there is sufficient steering effort available and to prevent engine stall. You should be able to hear this when you turn the wheel. If you don't, it is very likely the switch terminals are coverd in crud and dirt, making the switch ineffective. (There is only 5 volts across the terminals and they go high resistance very readily). Take the connector off and clean the terminals.
Turning car wheels that are not rotating takes quite some effort - try it in a car without PS! Above idle speed during normal driving the pressure switch function is not necessary as the engine is rotating fast enough to operate the PS system without the driver sensing it.
 
#22 ·
Almost right mate. The switch is activated as soon as the steering wheel is turned, if only a few degrees. It is then it provides the xtra assistance to the engine to operate the PS pump. If you do "blow" a switch you can be assured of a mess in the engine bay as the hydraulic fluid can be under several thousand kPa when it escapes. Try this - grab the high pressure hose from the pump and have someone turn the wheel. You'll feel the hose flex and swell in your hands. This will tell you how much pressure is at work in the system.

Cars with PS should never be turned to full lock against the backstop. This causes excessive pressure to be built up in the system. Under these condiitons a relief valve should operate to relieve most of the excess pressure. This can also cause belt slip and squeal. The car can be turned to full lock, but only momentarily. Pull the wheel back only a cm or two before making a turn. This won't affect your your turn, but it will keep the hydraulic pressures under control.
 
#23 ·
well i have learned something new. switch to make revs increase at low speed, my XG with its XF type steering could do with this as it seems to idle a bit slow for the pump the old crossflow motor never dropped revs as much as the 4.0 at idle speed turning,VERY INTERESTING
 
#24 ·
My pressure switch was leaking and i replaced it not long ago, I asked on these forums for help and they were very helpful. Its easy to replace just as long as its not too tight i had no fun getting mine out! I think all the switch does is stop the car from stalling under heavy load. Correct me if I'm wrong. Switch only cost me $40 from repco.

Ben
 
#25 ·
The switch isnt activated, it is constantly sensing fluid pressure.

It doesnt increase idle at all, mechanical resistance from the pump reduces idle as it is harder to turn (essentially it is placing more load on the engine), the ecu realises the idle speed has dropped and the idle control motor increases revs to accomodate. It has nothing to do with the switch.

The switch is there for problem diagnosis, it sense's pressure (both low and high) and when it falls outside of these specifications it logs a fault code. If anyone has ever had the option to watch their vehicle (or do the test on their own) when it is hooked up to a scan tool to check trouble codes, you can see there are a bunch of codes that relate to the power steering. Low pressure, high pressure, sensor out of range, failure, they are all logged.

Since fault code scanning is done periodically at the dealership, a problem should be found before it creates a big problem with the power steering system (excessive pressure, leaks, low pressure, increased wear, etc)
 
#26 ·
G'day. Interesting comment Madhatter. I agree with you about the mechanical load imposed on the engine by the pump. The engine revs will droop, and the ISC may well activate to compensate for that. It does work because if you idle the car along in first gear (I have a manual) the ISC will attempt to keep the revs around 700. You can feel it compensating.

But I'm not so sure about what you're saying with the PS switch. It is simply a switch activated by pressure, and can't modulate to sense changes in pressure, apart from either high - or low. In the Gregorys there is not any reference to a series of fault codes from the PS switch - at least not for E series cars. There is just one code 521 that says PSPS open circuit. The narrative on the sensor says that it should signal the ECU when steering wheel is being turned. I'd say the fault code would be generated if the ECU did not receive a PSPS signal when it expected to.

I'll stick by my theory that the PSPS works (maybe) with the ISC to kick up the idle for when the power steering is called on, particularly when the car isn't moving during parking manoeveurs and when all good drivers turn their wheels lock to lock with the car stationary! Once you're mobile and the engine's spinning enough to provide all the necessary grunt for the power steering, the actions of the PSPS are irrelevant.

It's only a very simple switch like an oil pressure switch. Other sensors on the engine give info like out of limits/high/low etc such as the TPS and HEGO sensors. But not the PSPS I don't think. If it had any real purpose to give indications of trouble, it would want to do it for the driver there and then at the time, and well before the car made it to the dealership for an (in)frequent service. Power steering systems are not really very complicated, and they usually give instant and dramatic notice if they are not happy!

But if you can expand on your theory, I'd be interested.

Cheers.
 
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