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Gauge Questions ...

ballcock

Well-known member
Joined
22 Jul 2008
Messages
3,011
Hi all, I'd appreciate thoughts on some queries re the voltmeter and the oil pressure gauge.
Firstly , how accurate are they, and are they 'buffered' like the temp gauge?

My pressure gauge doesn't go above 4.5 bars even at first start (my 993 is always up at 5 to begin with) and it appears to be quite 'laggy' compared to the 993 when the engine is warmed up and accelerating hard. Is it looked on as an accurate gauge? As an aside I've just replaced the sender.

WRT to the battery gauge, it seems to fluctuate between 12.5 and 14V, it normally drops to 13V under load (AC, lights, wipers etc on) and maybe a bit lower again if the engine is at idle. Is this normal gauge behaviour?
I suspect an alternator change is looming.

Thanks all!
 
No, that seems about right ballers, a spot more oil will help keep the pressure up, mine was at the recommended halfway point but would not go over 3 and idled 0.5 hot. Topped oil to Max and now much like yours and much healthier pressure and yes not as whippy up and down as the 993 was.
Volt gauge sounds similar too, only way to check accuracy would be digital voltmeter on the alternator, if it's working and battery not dying then I'd say leave it alone.
 
Brill, thanks for your reply ..
Mine ideals hot at 1 bar, I thought that was very low! But it's full as per the gauge..
Was thinking of increasing to 10W50 to see if it'd help.
Your 0.5 bar gives me comfort tho :grin:
 
My 2 pennys :)

Ignition on and the oil gauge should read zero .. anything above that and replace the sender unit .

4.5 bar is correct on a cold engine .. it will drop off as it gets warm .

928 the other day and the needle jammed at max for a few seconds .. the sender was over reading and the gauge wont go higher than 5 bar so it jammed the gauge .

Pretty accurate if it reads zero at the start though ... ie if it reads less than 1bar when hot on idle then i would take that as a fault and want a seperate oil gauge check to confirm it .. in other words i take that seriously .

Dash volt meter .. take it with a pinch of salt .. not that accurate .. a true reading is done via a volt meter on the battery .

Basically ive repeated what Asterix said :D
 
Thanks DM (was hoping you'd comment!)
Mine has had the sender just changed, it was just reading max value up to then.
It's now giving good read outs except showing 1 bar once it's properly hot. This is too low I think.
I don't know if changing from 5W40 to 10W50 is going to make a huge difference tho?
 
1 bar is about right .. should be slightly over 1bar to be fair .

We as a garage dont go above 5/40 on these cars .

Please be aware though that you have a seperate warning light for low oil pressure .. that would flicker on a hot idle if there was actually an oil pressure fault .
 

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