Engine Surging with elecs

[Jim Bowen 1]

Noticed this during my mot.

 

I've noticed before that using elec windows can cause the engine to surge slightly, but was quite minor so never worried about it.

But during my mot when they switched the hazards on the revs were going up and down slightly in time with the lights flashing.

 

What could this likely be? An earth? Had a brand new alternator a while back so don't think its anything to do with that, but not sure where to look.

[virtuoso23 10]

Jim I have the same issue with mine, more noticeable when operating the passenger window, comes and goes though.

 

Still haven't figured it out.

[dr_mat 0]

Obvious thing is to check system voltages (and alternator output) while doing this stuff. A big voltage drop could cause issues with spark power I guess, but still, that's a bit weird.

 

 

A Corrado is for life, not just for the MOT.

[Jim Bowen 1]

Going to check voltages tomorrow, took it out today and seems to run a bit too lumpy on idle and then turning anything electrical on like high beam or elec window and the revs increase a bit and seems to run alright

[Jim Bowen 1]

Been out with the multi meter today. Tested it with fans running as they put wire a demand on the elecs as i have twin spal that draw full power instead of 3 stage.

 

With engine running from cold i get 13.75v at battery. It's that too low? I thought it was meant to be over 14v

 

With fans on and engine runing battery showed 12.85v and kept falling regularly to 11.85v, fans stopped after that as i think engine cooled off.

 

Fans on but engine not running showed 11.9v, when fans turned off battery showed 12.09v

[1200 bandit 10]

That is low voltage is the fan / v belt tight,what battery have you fitted

Check all earths,condition of the wiring

When l got my Corrado it had a 380 am fitted had all kinds of problems got 600am battery fitted now a lot better

[dr_mat 0]

13.75 while on charge (engine running) is only a little low, unless the battery is soaking a lot of current itself to recharge. I'd expect to see 13.8-14.2 while charging with minimal electrical load. The other numbers are low though. Sounds a lot like your battery is buggered tbh. However, if those fans have been retrofitted and the alternator can't cope, that would kill batteries no problems. Any idea what current the fans pull? Must be huge if a 90amp alternator can't provide more than 12.8v while it's running.

 

 

A Corrado is for life, not just for the MOT.

Edited June 3, 2018 by dr_mat

[Jim Bowen 1]

Might just get another battery and try it.

 

Something i do have is a noise from aux belt area on startup, i thought it was the tensioner bearing but i spose it could be the alternator, i tend to start car and spray some WD40 on around that area and noise goes away, or it'll make the noise for a few minutes and goes away on its own

[Jim Bowen 1]

Might disconnect one fan and see how it helps.

[1xshaunx1 27]

I’d try s battery swap with a known good one. Then start looking at alternator. A good fully charged battery should read more than 12.09v disconnect it and see what it reads, then you will see if you have a big power drain, if there is a difference that is.

Good luck Matey,

[Jim Bowen 1]

Luckily i have a great place near work who supplied the alternator and can test that. The battery does go flat after a couple of weeks of not driving car.

[dr_mat 0]

If you have an alarm fitted it's not unusual for the battery to go flat if it's not driven.. but this is exactly what kills batteries long term.

 

 

A Corrado is for life, not just for the MOT.

[1xshaunx1 27]

Any further forward on this matey

[Geeba 0]

Sounds like the alternator is being hit, alternators under load require more HP to run them, I learnt this when I did a small stint at the WRC, they wind the alternator right down when the car is in stage mode so as not to suck HP.

 

I usually buy a diesel cranking power battery and as higher amp alternator as I can, I went for the 120amp alternator, but yet to run it of course on the VR6 but have done this on other builds ;)