Help To Diagnose Power Steering Problem

[simon43]

I posted on the Phuket forum for an alternator repair shop, (because Chevrolet garage said my alternator was bad), but after having driven/tested this car, I'm not so sure the alternator is the problem!

The symptoms are that the power steering will switch on and off whilst the car is in motion, (the on/off is not regular, perhaps off for 1 minute, then on for 2 minutes etc).

When the power steering fails, no power steering warning light shows on the dash, and the car can still be driven, albeit some force is needed to turn the steering wheel.

Under these fault conditions, (and when the fault is not present), a voltmeter on the battery, (with engine running) indicates about 15 volts.

The alternator in the car is a rebuilt unit which Chevrolet installed about 4 months ago when the same failure mode of the power steering was present. This replacement unit did solve the original fault problem, but I still am not convinced that the replacement alternator itself is now faulty.

I understand that the power steering pump obtains it's electrical supply from the alternator, so surely the intermittent fault suggests some issue with either that pump or the electrical supply to it?

(If one or two of the alternator diodes had failed, then I think the steering fault would be present all the time, and the rectified voltage output would be low all the time).

Any suggestions as to what checks/measurements I can make, or can anyone suggest a competent repair shop in Phuket?? I have lost confidence in the abilities of Chevrolet...

Thanks

Simon

[katabeachbum]

15 Volt kills you battery in few hours. most electric components are 11-15 volt compatible, so they may not be damaged, but can malfunction. Lightbulbs last for a few days with 15 volt

Chao Fa east, north of zoo junction, left side going north, next to a supercheap convinient store, should be able to limit your alternator to 14,45V as a start. Lets hope thats it

[simon43]

I did some more checks on this problem.

With the engine off, the battery output voltage is about 12.4 volts, which seems OK.

After I start the car, the measured voltage (at the battery terminals, with alternator connected), gradually climbs to 15 volts. If I rev the engine, the voltage jumps to about 15.2 volts and the battery warning light on the dash comes on.

When the engine is initially switched on, and before the voltage has climbed to 15 volts, the power steering works OK, but then stops operating when the voltage is high. So it sounds as if the power steering has a safety cut-out which is operating when the applied voltage from the battery is too high.

So it sounds as if the alternator is generating an excessive voltage output which is causing over-voltage safety circuits/cut-outs to operate.

If this is the case - then I presume the alternator internal (I assume it is internal), voltage regulator is faulty. If that's the case, then I could resolve the problem by installing an external voltage regulator, (zenor diode).

Simon

[katabeachbum]

I did some more checks on this problem.

With the engine off, the battery output voltage is about 12.4 volts, which seems OK.

After I start the car, the measured voltage (at the battery terminals, with alternator connected), gradually climbs to 15 volts. If I rev the engine, the voltage jumps to about 15.2 volts and the battery warning light on the dash comes on.

When the engine is initially switched on, and before the voltage has climbed to 15 volts, the power steering works OK, but then stops operating when the voltage is high. So it sounds as if the power steering has a safety cut-out which is operating when the applied voltage from the battery is too high.

So it sounds as if the alternator is generating an excessive voltage output which is causing over-voltage safety circuits/cut-outs to operate.

If this is the case - then I presume the alternator internal (I assume it is internal), voltage regulator is faulty. If that's the case, then I could resolve the problem by installing an external voltage regulator, (zenor diode).

Simon

yep, looks like you PS protects itself from being cooked, clever thing

I would assume a cheap regulator could be found at supercheap, even possibly one sensing at battery, not at alternator.

there is also a parts-shop between Vachira and BKK hospital, right side going from BKK hospital, in the junction

afraid your battery has already been cooked, anything below 12,6 while resting is rather useless

[simon43]

I'd like to add an external regulator, since otherwise it's quite a task to remove the alternator from the vehicle. Having seen this over-voltage, I'm not happy to drive the car without a VR in place. It's my wife's car in Ao Nang, so unless I can find a VR in Krabi, her car will have to sit unused for the next week until I get a VR in Phuket.

I should think that any external VR would be suitable - the functionality should not be specific to any model of car.

does anyone know the Thai for 'voltage regulator'? (Apparently, the Thai for alternator is something like 'diecharge').

Simon

[katabeachbum]

I'd like to add an external regulator, since otherwise it's quite a task to remove the alternator from the vehicle. Having seen this over-voltage, I'm not happy to drive the car without a VR in place. It's my wife's car in Ao Nang, so unless I can find a VR in Krabi, her car will have to sit unused for the next week until I get a VR in Phuket.

I should think that any external VR would be suitable - the functionality should not be specific to any model of car.

does anyone know the Thai for 'voltage regulator'? (Apparently, the Thai for alternator is something like 'diecharge').

Simon

I would check the Amp of alternator to make sure regulator can handle it. If you cant find it anywhere else, most marinas/chandleries should have them, but at a price. In boats/yachts external VR are common as they need to sense on batterys far away from alternator

If you need to start engine at all, its better to remove belt pulling alternator to avoid cooking anything. without ac fan or headlights, it should run a couple of hours wo alternator

and you have just taught me what I already had senced, stay away from badgeneered Chevys in TH, as most parts need to be imported, thus the prices. Chev Zafira is a Opel

[simon43]

Brute force (temporary) fix suggestion:

If I slacken off the alternator drive belt slightly, this should cause some slippage on that drive and possibly reduce the maximum output voltage??

(Just trying to think of some cheap and cheerful solution...)

Simon

[katabeachbum]

Brute force (temporary) fix suggestion:

If I slacken off the alternator drive belt slightly, this should cause some slippage on that drive and possibly reduce the maximum output voltage??

(Just trying to think of some cheap and cheerful solution...)

Simon

slacken it more than slightly could work. what else does belt pull?

[simon43]

slacken it more than slightly could work. what else does belt pull?

Not sure - need to check - this could maybe help until the shops in BKK are open again to supply a rebuilt unit.

Now where is my spanner??

Simon

[simon43]

The alternator is buried in the engine area - no easy way to get at it.

I minitored the battery voltage whilst driving and can see that the over-voltage protection switches in around 14.5 volts.

How can my wife safely drive the car next week whilst I search for an alternator repair solution?

Easy - drive with the lights on...

With this extra current drain, the voltage measured at the battery does not rise above 14 volts and the over-voltage protection does not activate - and the power steering works correctly. If I rev the engine or drive too fast, then the voltage increases above the safe limit. If my wife keeps to 60 km/h max (for local journeys), and keeps her car lights on whether night or day - then all seems OK.

It's a very temporary solution of course, but gives me a time window to find a permanent solution.

Simon

[TommyDee]

buy a new alternator. get it fitted by a mechanic. job done.

fiddle around trying to fix an obvious mistake with another component is a wate of time and money, and in all likelyhood a very temp fix

this is your missus, on a quiet road, after dark, driving your car maybe breaking down. think about it. ( seriously) a new one is job done,

and the last dreamed up idea of loosening the belt is the most funyy ( sorry). the belt will friction contact to the pulley still, still turn it at the same RPM just burn the belt out too.

seriously, let a technician do it and have peace of mind

[simon43]

@TommyDee, having identified the problem as a faulty voltage regulator that resides within the alternator housing, I see no point in paying 30,000 baht fror a new alternator when a competent specialist can replace the failed VR. (Buying a new alternator is like using a hammer to crack a nut...)

My short-term solution to drive with the lights on is fine for a few days whilst I locate a repair specialist. My wife only has to drive a few km between our Ao Nang guesthouse and home, and her brother travels with her.

Based on Chevrolet's previous repair work, I have minimal ccnfidence in their repair abilities. I'd rather find an alternator specialist.

Simon

[TommyDee]

@TommyDee, having identified the problem as a faulty voltage regulator that resides within the alternator housing, I see no point in paying 30,000 baht fror a new alternator when a competent specialist can replace the failed VR. (Buying a new alternator is like using a hammer to crack a nut...)

My short-term solution to drive with the lights on is fine for a few days whilst I locate a repair specialist. My wife only has to drive a few km between our Ao Nang guesthouse and home, and her brother travels with her.

Based on Chevrolet's previous repair work, I have minimal ccnfidence in their repair abilities. I'd rather find an alternator specialist.

Simon

30,000 for an alternator? thats mega.

you will be able to find an alternator rebuilder I am sure. or a recon one. £650 is madness I agree