Not joined yet? Register for free and enjoy features such as alerts, private messaging and viewing latest posts and topics.

High RPM voltage rising

Discuss problems you have had or are having with your Z4
john-e89
Lifer
Lifer
Posts: 11026
Joined: Tue Feb 10, 2015 10:27 pm

High RPM voltage rising

Post by john-e89 » Wed Nov 22, 2017 4:31 pm

mjennings23 wrote: Wed Nov 22, 2017 3:55 pm 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?
New alternator and battery already Mark, both changed just before sale.

I’m so sorry you’re having these problems with it.
M roady...OEM CSL’s, strut brace, Remus back boxes, ZHP
MR2 MK 2
E89 35i project car...mapped 365bhp, M4 stoppers & wheels, KWV3’s, H&R front ARB, M3 front arms, strut brace Eisenmann cat back race exhaust, VRSF downpipes inbound
E89 35is
G29

mjennings23
Senior Member
Senior Member
Posts: 1176
Joined: Tue Mar 21, 2017 11:11 pm
Location: North West

High RPM voltage rising

Post by mjennings23 » Wed Nov 22, 2017 4:47 pm

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 :rofl:

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! :headbang:

User avatar
Ducklakeview
Lifer
Lifer
Posts: 6362
Joined: Tue Mar 22, 2016 4:08 pm
Location: Merseyside

High RPM voltage rising

Post by Ducklakeview » Wed Nov 22, 2017 4:56 pm

mjennings23 wrote: Tue Nov 21, 2017 3:54 pm To clarify, the 18v was read from the OBD port, not a multimeter across the battery.
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

mjennings23
Senior Member
Senior Member
Posts: 1176
Joined: Tue Mar 21, 2017 11:11 pm
Location: North West

High RPM voltage rising

Post by mjennings23 » Wed Nov 22, 2017 5:15 pm

Ducklakeview wrote: Wed Nov 22, 2017 4:56 pm
mjennings23 wrote: Tue Nov 21, 2017 3:54 pm To clarify, the 18v was read from the OBD port, not a multimeter across the battery.
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
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.

User avatar
ph001
Lifer
Lifer
Posts: 3870
Joined: Mon Oct 31, 2016 5:53 pm
Location: N. Yorkshire.

High RPM voltage rising

Post by ph001 » Wed Nov 22, 2017 5:29 pm

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!!
2007 E85 Z4 3.0Si manual :driving:
19" CSL's | Eibach Springs | Aeroskirts | Z4M front bumper | Clear brake light | ZHP | RCH+| Stubby

2004 E46 M3 coupe manual - gone but not forgotten.

Image

User avatar
Ewazix
Lifer
Lifer
Posts: 4721
Joined: Sun May 02, 2010 5:30 pm
Location: Somerset

High RPM voltage rising

Post by Ewazix » Wed Nov 22, 2017 7:11 pm

Couple of thoughts ....... you mentioned blowing fused/components so it's a voltage surge rather than spike, if voltage surges after the seats have been on for a bit it's probably because they are switching out once warm, the alternator has been producing a high current and is reducing output too slowly, causing a brief surge. I'd have suspected the regulator/alternator, but since you have swapped out the reg' a bad earth or connection (battery, block, alt' or ECU, or seats maybe?)

Chances are surges are occurring with other high draw components like heated glass but not high enough to trip warnings, if so other damaged components will start to pop-up so I wouldn't just leave the seats off and hope TBH.
2003 2.5 SE, low miles, Sterling Grey, 108's & Eagles, no stubby here! Unmolested.
2018 Cooper S Countryman
Fiesta Ecoboost

mjennings23
Senior Member
Senior Member
Posts: 1176
Joined: Tue Mar 21, 2017 11:11 pm
Location: North West

High RPM voltage rising

Post by mjennings23 » Thu Nov 23, 2017 8:39 am

Ewazix wrote: Wed Nov 22, 2017 7:11 pm Couple of thoughts ....... you mentioned blowing fused/components so it's a voltage surge rather than spike, if voltage surges after the seats have been on for a bit it's probably because they are switching out once warm, the alternator has been producing a high current and is reducing output too slowly, causing a brief surge. I'd have suspected the regulator/alternator, but since you have swapped out the reg' a bad earth or connection (battery, block, alt' or ECU, or seats maybe?)

Chances are surges are occurring with other high draw components like heated glass but not high enough to trip warnings, if so other damaged components will start to pop-up so I wouldn't just leave the seats off and hope TBH.
Thanks for the input.

To clear it up, the voltage reported jumps to around 18v in one specific condition right now; heated seats are on and engine rpm exceeds 6k.

While, as John says, the alternator was changed quite recently, I'm still going to try a replacement this weekend, if for nothing else than to eliminate it from the probability. Monitoring voltages with any other electricals in any condition seems to maintain a steady 14v however.

mjennings23
Senior Member
Senior Member
Posts: 1176
Joined: Tue Mar 21, 2017 11:11 pm
Location: North West

High RPM voltage rising

Post by mjennings23 » Fri Nov 24, 2017 1:51 pm

So, collected a replacement alternator to try out. Also trying to do some digging and find a diagram showing ground points throughout the chassis to check, but it seems impossible to find in any simple diagram.

I believe there's a fair few near the steering column for the modules behind the dash, so will check these and also the B+ cable as best I can. Doesn't seem like issues that point to a bad cable but I'm just trying to eliminate possibles.

If anyone can point me in the direction of other ground points please do!

mjennings23
Senior Member
Senior Member
Posts: 1176
Joined: Tue Mar 21, 2017 11:11 pm
Location: North West

High RPM voltage rising

Post by mjennings23 » Sat Nov 25, 2017 5:42 pm

Seems the alternator fitted has gone bad unfortunately. Only noticeable under high electric load, but the replacement works perfectly.

Hopefully that's the end of the issue, I have a new Bosch part ordered from Germany which should be here in a couple of weeks.

Might also explain why I was never particularly impressed with brightness of the xenon bulbs...

mjennings23
Senior Member
Senior Member
Posts: 1176
Joined: Tue Mar 21, 2017 11:11 pm
Location: North West

High RPM voltage rising

Post by mjennings23 » Tue Dec 05, 2017 11:13 am

And for a final update, new Bosch unit fitted and all seems perfect. Hopefully that's the end of it, but now I think my front headlight leveling sensor is going bad too... Bloody cars :headbang: :rofl:

User avatar
Ducklakeview
Lifer
Lifer
Posts: 6362
Joined: Tue Mar 22, 2016 4:08 pm
Location: Merseyside

High RPM voltage rising

Post by Ducklakeview » Tue Dec 05, 2017 11:34 am

mjennings23 wrote: Tue Dec 05, 2017 11:13 am And for a final update, new Bosch unit fitted and all seems perfect. Hopefully that's the end of it, but now I think my front headlight leveling sensor is going bad too... Bloody cars :headbang: :rofl:
Did you raise the car to swap the alternator? If so the arm on the front sensor may have folded over on itself and will be giving the wrong readings. Worth a check?

Mike

mjennings23
Senior Member
Senior Member
Posts: 1176
Joined: Tue Mar 21, 2017 11:11 pm
Location: North West

High RPM voltage rising

Post by mjennings23 » Tue Dec 05, 2017 11:37 am

Ducklakeview wrote: Tue Dec 05, 2017 11:34 am
mjennings23 wrote: Tue Dec 05, 2017 11:13 am And for a final update, new Bosch unit fitted and all seems perfect. Hopefully that's the end of it, but now I think my front headlight leveling sensor is going bad too... Bloody cars :headbang: :rofl:
Did you raise the car to swap the alternator? If so the arm on the front sensor may have folded over on itself and will be giving the wrong readings. Worth a check?

Mike
Last time it was up on jack stands was the steering swap, so it could have happened then perhaps. It's been flashing on and off for a while.

The strange thing is INPA reads the code as short circuit to ground on the front levelling sensor sometimes, and others as open circuit on the same, yet when I turn the dipped beams on the warning light goes off. I'll have a play with it and see if moving it causes the lights to move up/down as expected.

Post Reply