Still got an issue, details below if anyone can help!
High RPM voltage rising
- Thread starter mjennings23
- Start date
I have no great insite or idea with electrics. But I do know I had a few isues with my car when the ground connection in the boot was a bit iffy. Worth checking it and also do the one in the engine bay.
If the voltage to the module goes over about 14.5-8v or so, it will trigger a code, as it alters the speed at which the ABS pump operates when it's modulating the fluid pressure. Get yourself a cheap digital multimeter and connect it to the cig lighter and watch the voltage. Does point to a faulty regulator pack in the alternator though, possibly one of the diodes has also gone.
Mike
Mike
Thanks guys, will check the grounds as a matter of course anyway, but I’m anticipating a new regulator may be the course of action. Perhaps a bit odd though as I believe the alternator is only a couple of years old, certainly looks a lot newer than the rest of the engine bay components.
Okay, so I managed to read the codes and, while I was daft enough not to record the code itself, the description was “Board voltage >18”, so quite clearly voltage is spiking at high rpms. My speakers have now also stopped working, so I’m hoping this isn’t the amp getting fried by voltage too! I’ve not had a chance to pull it out to check the fuse yet, hopefully it’s nothing more.
Where abouts do I find the main ground points? I understand there’s one linking the engine to the chassis underneath at the front, but the rear one?
Where abouts do I find the main ground points? I understand there’s one linking the engine to the chassis underneath at the front, but the rear one?
Regulator changed today anyway, not had a chance to properly run it to redline but voltage across battery stayed consistent for the rev range I checked up to 4K so hopefully all is good, was showing a gradual increase beforehand.
Oddly it was a TRW alternator so clearly been replaced at some point, either way the design seems identical to Bosch as the new Bosch regulator was a mirror match to the fitted one.
Oddly it was a TRW alternator so clearly been replaced at some point, either way the design seems identical to Bosch as the new Bosch regulator was a mirror match to the fitted one.
mjennings23 said:
They all tend to use the same solid state internal components from other manufacturers. They can manufacture the rotating components cheaper, but not the semiconductors on the scale they work at.
Glad it seems to have sorted the problem, clear the codes and hopefully your audio will be ok.
Mike
The amp is blowing its fuse constantly still, even when the car is off so I assume there must be some issue, it’s been sent off for testing anyhow so we shall see! For the sake of postage costs it’s no big deal.
So, I thought a new regulator had solved this, except it happened again last night. DSC module had code stored for >18v board voltage when checked.
Now, I'm hoping this is just an alternator ground issue now and will be checking that during the week. Past that coming up clear, it looks to be new battery/alternator time, which I'd rather avoid!
Now, I'm hoping this is just an alternator ground issue now and will be checking that during the week. Past that coming up clear, it looks to be new battery/alternator time, which I'd rather avoid!
Edit: Useless info!
At full throttle up to redline, in certain situations the voltage output spikes from a steady 14v to over 18v.
Now, after testing this weekend, this only seems to occur under heavy electrical load, and even then only when approaching redline on the engine.
For instance, tested with air con, heating, radio and lights all on. No issue.
Repeat test with heated seats on too, voltage spikes.
I have already changed the alternator regulator for a new Bosch piece, it was cheap enough to try and seemed logical. Seems I was wrong!
Would I be right in assuming this is pointing to a weak battery? Or could it be a bad ground? The only thing drawing me away from this is it only happening with high electrical draw.
Any advice would be greatly appreciated.
Thank you
Now, after testing this weekend, this only seems to occur under heavy electrical load, and even then only when approaching redline on the engine.
For instance, tested with air con, heating, radio and lights all on. No issue.
Repeat test with heated seats on too, voltage spikes.
I have already changed the alternator regulator for a new Bosch piece, it was cheap enough to try and seemed logical. Seems I was wrong!
Would I be right in assuming this is pointing to a weak battery? Or could it be a bad ground? The only thing drawing me away from this is it only happening with high electrical draw.
Any advice would be greatly appreciated.
Thank you
The increased voltage has to be coming from the alternator, as it's the only thing that can produce those sort of figures. Possibly bad windings or damaged slip rings? What was the condition of the brushes on the removed unit?
Mike
Mike
Very odd this. I'm assuming it starts fine? There is no way you should be able to get 18V on the battery (well not a healthy one anyway). The current into the battery rises exponentially once you get much above 15V. So if you tried to put 18V onto a good 12V battery, the current would be huge - probably more than the alternator could even put out.
If the battery is very oxidised, it's impedance (think of it as internal resistance) goes up considerably. Under these circumstances, applying 18V doesn't take nearly as much current as the batteries own resistance is high. BUT, a high impedance battery also wouldn't be able to supply much current so you expect very lazy starting. Something here doesn't add up.
I think my next port of call would be replacing the battery, just to remove it from the equation if nothing else.
If the battery is very oxidised, it's impedance (think of it as internal resistance) goes up considerably. Under these circumstances, applying 18V doesn't take nearly as much current as the batteries own resistance is high. BUT, a high impedance battery also wouldn't be able to supply much current so you expect very lazy starting. Something here doesn't add up.
I think my next port of call would be replacing the battery, just to remove it from the equation if nothing else.
Never had an issue with starting, worst case about 1 second of cranking on a below freezing morning.
The old regulator brushes looked fine, still have it at home, currently thinking it was working perfectly well and didn't need replacing. I'll take a photo comparing the two at the weekend to see.
To clarify, the 18v was read from the OBD port, not a multimeter across the battery. Not sure if the battery is to OEM spec however, it's a Bosch S3 unit, believe 096 size but haven't checked properly. What's the minimum amps and CCA for this car? Bosch website lists S4 as minimum. Wonder if that could be something.
The old regulator brushes looked fine, still have it at home, currently thinking it was working perfectly well and didn't need replacing. I'll take a photo comparing the two at the weekend to see.
To clarify, the 18v was read from the OBD port, not a multimeter across the battery. Not sure if the battery is to OEM spec however, it's a Bosch S3 unit, believe 096 size but haven't checked properly. What's the minimum amps and CCA for this car? Bosch website lists S4 as minimum. Wonder if that could be something.
Updates,
Tried a new battery today, no change. Same problem occurring.
Removed, cleaned and reseated engine and battery grounds, both showing resistance when checked as expected, and 0.0v across grounds.
So the next step may indeed be alternator, might pick up a cheap one from ECP for time being, at least that gives the option to return easily if it's not the cause.
The common denominator in all of these tests, however, if that it only happens with the heated seats on. Could this point to a grounding issue on the seat circuit?
Tried a new battery today, no change. Same problem occurring.
Removed, cleaned and reseated engine and battery grounds, both showing resistance when checked as expected, and 0.0v across grounds.
So the next step may indeed be alternator, might pick up a cheap one from ECP for time being, at least that gives the option to return easily if it's not the cause.
The common denominator in all of these tests, however, if that it only happens with the heated seats on. Could this point to a grounding issue on the seat circuit?
Nothing to worry about John, in honesty it just means I can't have a warm arse and blast the engine at the same time 
Well assuming its not a ground on the main power system, a bad alternator or a bad battery, that points to something wrong with the seat heaters themselves?
I bloody hate electrical issues, pain in the arse!
Well assuming its not a ground on the main power system, a bad alternator or a bad battery, that points to something wrong with the seat heaters themselves?
I bloody hate electrical issues, pain in the arse!
mjennings23 said:
THIS could be the issue. You need to get a decent meter across the battery and see the actual values, not just what the ECU "reports" as if, indeed the voltage is high, then that may also be affecting what the ECU is reporting..
Mike
Ducklakeview said:
Unfortunately the only multimeter I have is a handheld one, and I can't see any way to check that when I'm on a motorway. I could give it a go stationary, will check at the weekend. Other than that I'd be lost as to how you'd check.
I did check idle and fast idle across the battery and it read 13.9v, which is within the correct range. Haven't tried above 3k rpm mind.
You won't be getting 18V across a new battery. That much I can tell you for sure. The thing is, if the OBD is reading a peak of 18V, it could be very transitory, maybe just a few milli seconds. I'm just struggling to understand how this can be related to the heated seats. I'll go away and do some thinking!!