Technical Electric windows and also ammeters

[arc]

I didnt think these needed two seperate threads, so they're both in here.

Does anyone know if the electric windows are positive, or negative lift. I'm suspecting positive..

Ok, now ammeters. I know exactly what one does, and how to use one however i'm confused as to where and why people fit them in a car.

An ammeter must be wired in series with the circuit its monitoring, so for an ammeter to be any use on a car, you'd need wire it between the body and the negative battery terminal, yeah?

Well, when a car starts it draws massive current - but after that it levels out a lot lower doesnt it. So any ammeter would have to deal with a high current, but then also swap to displaying low amounts of currents. Large currents with decent accuracy sounds expensive, something car ammeters are not.

Also, the cabling to the bloomin thing would have to be huge - unless it has some sort of sending unit.

So yeah, ammeters - is there any possible reason for using on on a normal car?

 

[arseofbox]

Well, when a car starts it draws massive current - but after that it levels out a lot lower doesnt it. So any ammeter would have to deal with a high current, but then also swap to displaying low amounts of currents. Large currents with decent accuracy sounds expensive, something car ammeters are not.

So yeah, ammeters - is there any possible reason for using on on a normal car?

Id personally expect it to be accurate +/- 5A at a push. It'd be cheap, not a precision instrument.

Uses, Id say few, other than for checking the alternator is kicking out the right currrent. Is this anything to do with Viv's idea for the Smartie?

A voltmeter on the other hand would be much more useful. In fat, bugger that! Fit a DMM in - Pimp My Ride styleé

 

[arc]

my point is tho tom, for it to be checking the alternator - you'd have to have it between the battery and the main earth - and then run 4awg cable to the ammeter. It'd be useless.

Nothing to do with Hazel (the smart) - i was just pondering, and still need something to fill the other guage pod!

 

[JonnyBoy]

my point is tho tom, for it to be checking the alternator - you'd have to have it between the battery and the main earth - and then run 4awg cable to the ammeter. It'd be useless.

Nothing to do with Hazel (the smart) - i was just pondering, and still need something to fill the other guage pod!

Most ammeters in a car don't actually take the full charging current (~30 or 40A); instead most of them are actually a voltage meter that displays the voltage between the battery's positive terminal and earth. There may still be amp values on the scale, these are estimates based on the internal resistance of the average car battery. A reading of 12v (the middle point on most ammeters) indicates that the battery is neither charging nor discharging. Under 12v indicates current flowing out of the battery (e.g. when the starter motor is operating); over 12v indicates that the battery is being charged by the alternator.
Wiring one of these in is a piece of p*ss... connect the earth terminal to earth, the live terminal to a switched live (the one for the radio will do), and if it's a posh one there might be a backlight to connect to the sidelight circuit too.

 

[arc]

so its not an ammeter, its a dodgy calibrated volt meter. I see!

 

[arseofbox]

Fill it with a lambda sensor thinger...

 

[arc]

i have my eye on a posh gauge to go there, but its expensive

the electric windows are positive lift by the way people

 

[JonnyBoy]

EGT (exhaust gas temp) gauge? All the Jap turbo nutter cars have 'em

 

[arseofbox]

EGT has no real relevance from a tuning stand point unless the ECU knows what to do with it...otherwise its useless knowing it (unless its there to make sure you dont melt the exhaust )

 

[arc]

hehe, ETG not much use imo on an NA car.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=7962650255&ssPageName=ADME:B:WN:UK:1

I'm after something like that i think, not that i can afford it like.. but still

 

[JonnyBoy]

EGT has no real relevance from a tuning stand point unless the ECU knows what to do with it...otherwise its useless knowing it (unless its there to make sure you dont melt the exhaust )

I know, but it looks cool

 

[arseofbox]

Fair Point. I can see where youre coming from

 

[Liam]

If the exhaust gas is crazy then surely the engine and turbo are being affected but I'd suspect another standard guage or the car itself would tell you this.

Liam