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[Brucie1946]

I have a 98 MV6, which recently started to misbehave, the power sounder siren went off whilst I was starting the car one morning, and went off in the carpark at work, much to my annoyance.  Im not sure if its connected to the fact I remove and checked all fuses after the car had been sat a few months not being used, for a general check to see if any had blown.

Anyway, I replaced the power sounder with a new one from Vaux, I didn't have problems again until 6 weeks afterwards, whereby the power sounder went off again, then also whilst driving (no lights flashing), I reckon it went off when the cooling fan started to reduce the coolant temp, almost like a dip in voltage had triggered it going off.

With that I replaced the power sounder again under warranty, with Vaux, this was last weekend, the power sounder went off immediately as I plugged it in, for some strange reason, so I charged the b attery a little and it plugged in without a sound ( I had read dave dnd's post about the threshold voltage maybe being low, and the siren thinking it was being stolen due to the voltage drop, not sure but the charging session for 1.5 hours seemed to work, so I left it at that.  Monday evening the siren went off again whilst driving, proving that the siren wasn't at fault, but the fans had kicked in again, my reckoning the power sounder responded by going off due to a voltage drop?

I said earlier about the fuses, well I had another problem a couple of weeks back, whereby I had removed the heated seats/central door locking fuse, and with the fuse being a bit tarnished, the doors refused to open one afternoon, after a 2 hour session of undoing the rear seat button I climbed in and wiggled the offending fuse and the door locks went  up whilst at the same time blipping the keyfob, hence my thought with the link to the tarnished fuse not letting any voltage through after it being disturbed to remove it, I cleaned the fuse blades and the central locking has behaved itself once again.

I read today that the coolant fan works off fuse 15, as does the power sounder, again I removed it and cleaned the blades, as they were grey tarnished and put it back in, not that I thought this was the offending problem, but I gave it a go.  The powersounder going off when the fan kicked it was maybe coincidence, but I thought they maybe were linked?  We'll see?

Anyway, yesterday I checked the battery voltage with the battery specialist I bought the battery from and they told me it was 13 volts, which was good, as it was only replaced 6 weeks ago.  The technician asked me to start the car, the battery voltage then went up to 13.8 volts at idle, we revved the engine only to see that this voltage didn't budge.  I was then asked to load the system (heated seats, rear window, radio, xenons), the voltage then dropped to 13.5 volts, again revving the engine to around 2000 rpm, it didnt budge again, is this normal?  I would of thought it would of increased?

I rang a alternator specialist today, told him the voltage story from yesterday, and he asked me if I had a bosch system?, I replied yes, he then told me that this was perfectly normal for the bosch system, and I would see no more than 13.8 volts! even when revving, as this is a bosch characteristic so he told me.  If it were an AC Delco system, the voltage would increase beyond 14 volts, but not for my car he told me???

I've exhausted myself in researching it now, and getting confused by the day!

I'm going to replace all the fuses, as thats definately caused me problems in the past, tarnished fuse stopped current to central locking that time.  So thought it could do no harm.

I've also read Mark DTMs alternator guide, but not removed anything yet, as I have only chatted with supposed specialists, is that right about the bosch system, or am I being strung a yarn?

Could it be a faulty voltage regulator?  Or maybe could I have cured it now by cleaning fuse 15, and now to subsequently replace all fuses with new ones to make sure I get a good circuit, as I know corroded contacts can cause a voltage drop, hence my reason for cleaning fuse 15 because of its link to the fan and the power sounder?

Sorry to go on, just wanted to tell you the complete story!

Can anyone help please?  especially the boy or marks DTM?

Cheers

Dean

[Diamond Black Geezer]

Just to confirm, you've spoken about 'the battery', are you referring to the small battery for the alarm, remember the power sounder doesn't get its power directly from the main under-bonnet battery, it only trickle-charges a smaller battery inside the offside wing for the sounder.

Changing the power sounder would do nothing, certainly changing it twice even less!

When the battery gets old (often something like about 10-odd years old) it doesnt charge as well as it used to. When the sounder senses reduced power it reads this as a wire's been cut ie: someone trying to break into me, thus the alarm sounds.

As a cure many remove sounder, best to remove the battery too, as they are known to cause fires (!) Though I personally would favour replacing the battery with another suitable.

It's a common fault, and the drain from using various fans etc. would be consistent with a poor/old battery, causing the sounder to go off. If Vauxhall didnt make you aware of this and just sold you a new sounder, thats just an example of so-called experts being thick. If you know all I've just typed already and I've answered a question you never asked, well that's just an example of me being thick!

 

[fiend61]

(Anyway, yesterday I checked the battery voltage with the battery specialist I bought the battery from and they told me it was 13 volts, which was good, as it was only replaced 6 weeks ago)
hmm dont think its refering to powersounder battery DDG
i would have thought that revving the engine would increase the voltage to more than 13.8v more like 14.8v but not sure about the bosch  i will try and find out though 

[Kneepad]

This may not be what you want to hear, but I would disconnect it, take the sounder out and bury it deep.

Or as it's new you might get some of your money back on ebay. 

[fiend61]

nominal charging voltage of a bosch is reputed to be 14.1v because of the voltage regulator, just fishing here but are you sure that the battery has all good cells ? holding charge?

[fiend61]

oh and as kneepad said disconnect the powersounder and as its nearly firework night find the biggest rocket you can find and send it to the moon 

[Entwood]

If the powersounder is being triggered by spurious low voltages, removing it will not solve the underlying problem.

I would check all battery terminal connections, as well as the battery in order to find the true fault.

[Brucie1946]

Battery is a varta silver, one of the best you can buy, was replaced 6 weeks ago and is perfectly fine, chap is a battery specialist having traded for 30 years.  He put me onto an auto electrician, who said voltages do appear normal, under no load and with load.  He did say check fuses and feed to alarm siren, also earth points, its interesting about fuse 15, which ive cleaned up this evening, definately want to find out more about the alternator though, my Mid display does dim and brighten ever so slightly as mark mentions are possibly early signs of voltage regulator playing up? But definately would like to confirm this? Maybe mark dtm might lend his knowledge soon?

BTW Im not going to bin the powersounder, as I just bought it, and want everything on the car to work as it should!

Cheers Dean

[Kneepad]

If the powersounder is being triggered by spurious low voltages, removing it will not solve the underlying problem.

I would check all battery terminal connections, as well as the battery in order to find the true fault.

I appreciate what you are saying, but the underlying problem appears trivial compared to the main problem of the sounder going off randomly.
Would the underlying problem be a problem at all if there was no power sounder. 

[fiend61]

yup could be the voltage regulator starting to fail, does anything else dim when the mid dims? or as already been said check earths and battery connections  :-/
when mine started to play up my instrument lights were dimming slightly and the more load i had on the more they dimmed including headlights but mine was just a dodgey connection

[Kneepad]

  BTW Im not going to bin the powersounder, as I just bought it, and want everything on the car to work as it should! 

I fully respect your right to make that decision. 

[Kevin Wood]

If you run the engine with a few electrical loads on does either of the battery terminals get warm?

The crimps, especially in the positive terminal, can work loose leading to poor charging.

Kevin

[Brucie1946]

Cheers for the replies, the battery terminals are all tight as the new battery was put on 6 weeks ago, but will check.

Not had the problem since monday evening with the power sounder, when I think the voltage drop from fan coming on triggered it, Im sure the same happened the other time whilst driving, but not 100%.

Fuses will all be replaced this weekend, as I was told to check these, and with previous experience with the central locking not working by removing the fuse rings true, there wasn't a problem at all until I disturbed them to check if any were faulty back in June, hence why Im intrigued by that theory, the grey tarnishing from experience causes poor contact Ive proven that.

Still puzzled by the alternator though not inducing any more charge under load when revved over idle than 13.8 volts with no load and 13.5 with load? Can anyone confirm this?

In the meantime, Ill check earths under battery and clean up, the electrician said it might be linked to what feeds power to the siren, fuse 15?

Keep the replies coming.

Regards

Dean

[fiend61]

found this ---Unfortunately Bosch seems to think running the alternator output at about .01 volts higher than the battery is enough. OK, it's actually in the high 13's, a full volt or so higher, but it often seems rather insufficient.
which confirms the 13.8v 

[henryd]

Cheers for the replies, the battery terminals are all tight as the new battery was put on 6 weeks ago, but will check.

Not had the problem since monday evening with the power sounder, when I think the voltage drop from fan coming on triggered it, Im sure the same happened the other time whilst driving, but not 100%.

Fuses will all be replaced this weekend, as I was told to check these, and with previous experience with the central locking not working by removing the fuse rings true, there wasn't a problem at all until I disturbed them to check if any were faulty back in June, hence why Im intrigued by that theory, the grey tarnishing from experience causes poor contact Ive proven that.

Still puzzled by the alternator though not inducing any more charge under load when revved over idle than 13.8 volts with no load and 13.5 with load? Can anyone confirm this?

In the meantime, Ill check earths under battery and clean up, the electrician said it might be linked to what feeds power to the siren, fuse 15?

Keep the replies coming.

Regards

Dean

your battery terminals may well be tight but what kevin means is where the wires enter the terminals the crimp joint can fail and lead to high resistance,hence the terminals getting warm in use