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Would a lower voltage cause temperature guage to read a little lower?
Jasongray5 - 3/8/11 at 02:04 PM

Hi guys,
A little background info,
I have a ford falcon (EB model) here in Western Australia, The alternator has been on its way out for some time, and only giving around 12v. The other evening, it decided it would be a good idea to die, 140k's from anywhere. So, I have replaced it, and getting a steady 14.5
Around the same time, the temperature guage has started reading ever so slightly higher, nothing to worry about heat wise, could this be because of the difference in voltage?
She has plenty of coolant, and that was only changed 12,000k or so ago.
I am moving steadily north at the moment tho, so the air temperature has changed from 15 degree's to 30 or so?
Cheers for any thoughts!
Jason

wylliezx9r - 3/8/11 at 02:24 PM

Could well be, as the sensor is sending out a voltage in relation to the temperature. I'm sure somebody will be along to correct me though.

britishtrident - 3/8/11 at 02:51 PM

I would expect on an older model it would but I don't any details at all about your specific car model.

Modern euro box cars ie anything post 1998 or so tend to drive the dashboard instruments from the engine ECU and give readings that are non-linear ie they are programmed to remain smack on "N" between 75c and 115c -- this has caused a lot of blown head gaskets.

ashg - 3/8/11 at 03:00 PM

i would say its more to do with the new alt putting extra load on the engine tbh. temp sensors work on ground resistance so voltage shouldn't have any effect. the 12v feed to the gauge is only required for mechanical movement which will just be faster or slower depending on voltage not more or less movement.

Liam - 3/8/11 at 03:27 PM

Supply voltage shouldn't affect instruments in a modern car or they'd be all over the place under different electrical load/revs/etc.


quote:
Originally posted by Jasongray5
Hi guys,
A little background info,
I have a ford falcon (EB model) here in Western Australia, The alternator has been on its way out for some time, and only giving around 12v. The other evening, it decided it would be a good idea to die, 140k's from anywhere. So, I have replaced it, and getting a steady 14.5
Around the same time, the temperature guage has started reading ever so slightly higher, nothing to worry about heat wise, could this be because of the difference in voltage?
She has plenty of coolant, and that was only changed 12,000k or so ago.
I am moving steadily north at the moment tho, so the air temperature has changed from 15 degree's to 30 or so?
Cheers for any thoughts!
Jason


There must, must be a clue in there somewhere, but I'll be damned if I can see it. Anyone know Sherlock Holmes' number?

[Edited on 3/8/11 by Liam]

britishtrident - 3/8/11 at 03:48 PM

But a voltage regulator can't compensate for low voltage once it is below a given threshold.

On older cars the instruments tended to be the bi-metal type which were very voltage sensitive.

Dingz - 3/8/11 at 04:08 PM

I would say you are right about the higher voltage, I don't have a voltage stabiliser on my instruments in my kit, when I turn the headlights on my fuel gauge drops, turn them off and it fills up again.

Jasongray5 - 4/8/11 at 11:38 AM

Cheers for the replies guys!
I think its going to be a case of keeping on going, until something dramatic happens!
Jason