Fiat Coupe Club UK

low oil-pressure indicator on, whilst car is off?

Posted By: dante giacosa

low oil-pressure indicator on, whilst car is off? - 15/04/2018 20:35

Hey team,

interesting time this evening- I was just in the first stages of recommissioning the VIS for the first of this years' outings, when I noticed that the low oil-pressure light was on- whilst the car was OFF!

Quite pleased to have spotted it actually, as the car has developed a habit in the last year of going totally dead for really 'no reason', which is annoying, as I am on it in terms of usage/recharge cycles.
So, it's good to find a reason for an invisible problem.

I'm sure I've heard about this before, and it's obviously indicative of an earthling issue of somekind. Can anyone be a bit more specific about avenues I should pursue in terms of an investigation.

Just before this, I had jet washed out the wheel arches of winter filth. Oil pressure is genuinely fine.

Here's a question; does the low oil-pressure switch go-to-ground when the oil pressure drops / or is it nominally grounded and goes 'high' when the pressure drops?
P.S. is the low oil-pressure switch really 'near' the alternator, as the schematics suggest..?!



Posted By: Morrison

Re: low oil-pressure indicator on, whilst car is off? - 15/04/2018 23:08

Think it means the alternator is dead or dying. Would explain the going flat over the last year.

I'm sure someone with more knowledge than me will post to correct me and point you in the right direction!
Posted By: dante giacosa

Re: low oil-pressure indicator on, whilst car is off? - 16/04/2018 04:12

Actually-

That would 'kind of' make sense- I seem to recall an indicator fault like that being indicative of this symptom in the past myself...

But I thought it was a low voltage indicator...

Thanks Morrison...
Posted By: Anonymous

Re: low oil-pressure indicator on, whilst car is off? - 16/04/2018 08:12

Probably diode pack in the alternator.

There was a recent thread with same problem:

https://www.fiatcoupeclub.org/forum/ubbthreads.php?ubb=showflat&Number=1617692
Posted By: dante giacosa

Re: low oil-pressure indicator on, whilst car is off? - 16/04/2018 08:27

Thankyou, Graham

and thanks for including that link

I 'thought' i remembered something about this from the distant past

Do you think it's possible to swap the diode pack 'back' on the alternator, with it in situ?
I know the standard option would be to replace the whole unit. I have a replacement alternator to hand, left over from 'nearly' having a problem on the 'West Coast Tour '16.
(Joe sent me up a 'known-working' replacement from a VIS with A/C)
Posted By: Anonymous

Re: low oil-pressure indicator on, whilst car is off? - 16/04/2018 08:35

Never done it myself but I'm pretty sure the alternator needs completely removed to dismantle it.
Posted By: DaveG

Re: low oil-pressure indicator on, whilst car is off? - 16/04/2018 08:40

I'm not sure about the VIS, but on the 20vt there's very little room making it hard to do in situ, easier to remove the alternator, but this entails moving the A/C compressor out of the way (if fitted) after removing the radiator fans and draining the coolant to allow removal of the pipe leading from the coolant reservoir to the coolant rail, plus moving the oil cooler out of the way to allow the long bolt to be removed from the bottom of the alternator. AFAIK there's no external air/oil cooler on the VIS so that bit should be easier.

Maybe there's just enough room to do it in situ on the VIS but I think I'd rather remove the alternator, this thread gives some tips
Posted By: dante giacosa

Re: low oil-pressure indicator on, whilst car is off? - 16/04/2018 08:46

Thanks Dave, Graham-

yes; I'm absolutely certain it'll be easier to do with the whole unit removed!

But, I'm trying to scrape a result, without significant expense, at this point in the year.

My VIS does have A/C, but doesn't have the whole turbo-arrangement on the exhaust manifold (oddly enough!), so access is 'poor' but 'better' than the VT.
I'm just wondering if the black-plastic part of the alternator catches the spindle itself within the body of the unit, or whether it is modular, and removable 'theoretically', with the pulley still engaged outside the unit.

I'm dreaming really, aren't I?!
Posted By: DaveG

Re: low oil-pressure indicator on, whilst car is off? - 16/04/2018 10:47

I've just updated my post on alternator overhaul so that the pics are all working.

Even on a 20vt the turbo and downpipe stay in place, but you still need to drain the coolant, remove the water pipe and move the A/C compressor out of the way to be able to reach the alternator for removal. I suspect that in situ you will find it hard to reach all 3 nuts to remove the rear cover and more likely find it hard to undo the other 3 bolts, and may end up rounding them off if you're not careful, but hey, worth a try, eh?
Posted By: dante giacosa

Re: low oil-pressure indicator on, whilst car is off? - 16/04/2018 10:52

I think, to say it it will be 'hard' is an understatement!

But; i'll have a look.

I have just seen your updated thread with pictures; it is tremendous; thank you.

Can I ask; would it be accurate to say, that all the electrical parts which fail or need replacing (in the context of my fault) are in the removable section, as identified win your thread?
Or are there further higher-power diodes further into the unit, which classically need replaced in a deeper refurb..?
Posted By: DaveG

Re: low oil-pressure indicator on, whilst car is off? - 16/04/2018 11:11

I only went as far as removing the regulator, the rectifier (with diodes I assume) is the C shaped thing underneath with "fins" and may prove difficult to remove. What voltage do you see when the engine is running? If it's out of the normal range then hopefully it's just the regulator.
Posted By: dante giacosa

Re: low oil-pressure indicator on, whilst car is off? - 16/04/2018 12:01

Ha!

do you know- I've never measured it!

I wouldn't trust the gauge for accuracy, although oddly enough it has been showing 'low' for a couple of years now...
I'll stick the Fluke on it later on for a reading.

Just been down to the garage to see the car; access will be 'difficult' shall we say.
Technology prevents me from posting some pictures that I got from behind the radiator fans, but I can see about 80% of the rear of the alternator, as it sits.

What I cannot see however, is the tensioner pulley for the inner aux belt...
Posted By: Heatseeker

Re: low oil-pressure indicator on, whilst car is off? - 16/04/2018 12:49

i m afraid to tell you ..but your alternator is no good
Posted By: DaveG

Re: low oil-pressure indicator on, whilst car is off? - 16/04/2018 14:41

To release the tensioner pulley you need the "sawn off allen key" tool or similar, you can locate it by following the route that the belt takes around the pulleys, the long tensioner bolt screws into am elongated "nut" attached to the pulley. Have a look up to step 4 on this How To
Posted By: dante giacosa

Re: low oil-pressure indicator on, whilst car is off? - 16/04/2018 15:25

gosh-

what a resource that is; I've never seen that before.

Thanks for your help.
Posted By: dante giacosa

Re: low oil-pressure indicator on, whilst car is off? - 16/04/2018 19:56

well.

I've done it.

And if I can overpower image-hosting, then I'll get some pics up.


Hey Heatseeker; why do you say that..?
Posted By: dante giacosa

Re: low oil-pressure indicator on, whilst car is off? - 16/04/2018 21:13

okay-

lets go; here is how it worked out;

I had to take this stuff off (you will only recognise this if you have a VIS!)

click to enlarge

and that gave a view like this;

click to enlarge

which allowed me to see along to the rear of the alternator;

click to enlarge

and get the back, and regulator-pack off (sorry; this one is through 90 degrees)

click to enlarge

for what it's worth; the legacy (left) and 'known-working' (right) regulator-packs

click to enlarge

and here is everything hooked up again

click to enlarge

THANKYOU GrahamL & DaveG

JimP
Posted By: DaveG

Re: low oil-pressure indicator on, whilst car is off? - 16/04/2018 21:48

Well done! And you are welcome. Maybe I should have tried repairing mine in situ, but I do think that the turbo-thingummy, downpipe and oil cooler pipes get in the way on a 20vt.

Did you measure the voltage before and after?

And did that large fan-shaped cowling in the first pic really come off the car?
Posted By: Anonymous

Re: low oil-pressure indicator on, whilst car is off? - 16/04/2018 21:54

So is the oil pressure light now out?

Yes, I don't think this method would be possible on the 20vt, but interesting to see the pics of the VIS are there are so few around.
Posted By: dante giacosa

Re: low oil-pressure indicator on, whilst car is off? - 17/04/2018 05:46

The fan shaped cowling covers a cold air intake pipe that goes across the radiator and presents itself behind the front grill, just inboard of the OS fog light.
The intake pipe is in that picture too.

Yes- I don't have the oil-cooler (yet), or a turbocharger, or twin-radiator fans, so it was okay, actually.
Biggest difficulty, was the final OS bottom self tapper for the radiator fan - I'll have to come back to that! Three out of four ain't bad.

I did measure the voltage before and after and it was 'the same', as in 14.10 before, and 14.14 after. (Car running)

But the battery is brand new (alright: I got it in November and have used it in another car twice)

And no Graham- the oil pressure light wasn't on, afterwards.
But then- I had never seen it on before until Sunday night. I think what has happened here, is that I have luckily 'just noticed' something that has been on the go for a while (intermittently), but that I've never seen.

The proof of the pudding will be in what happens now!

I did have a concern, halfway through last night, that the power-diodes that generate the current within and alternator, are still deep down inside the body of the thing, and that I wasn't swapping those out. (Perhaps this is innacurate?)
But, looking at the schematic, such diodes could never lead to a positive back-feed up the battery indicator line (and on into the oil pressure indicator), so I really do believe the regulator-pack is 'it'.

But as I say- we'll see

THANKYOU, all for your invaluable assistance.
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