AMPS or VOLTS gauge better choice?

steptoe · Post by **steptoe** » Tue Nov 17, 2009 9:00 am

Is it better to fit AMPS or VOLTS gauge to monitor the health of the charging and power supply system of an old MY or L Series. Never had either , figure VOLTS is a better indication. Comments and experience appreciated, Jonno

AlpineRaven · Post by **AlpineRaven** » Tue Nov 17, 2009 1:28 pm

for me, voltage. But if you have lights and heavy current load then amps would be good indicator.
Why voltage? Because one day i was driving around with faulty regulator on the alternator and it rose to 19 volts which is good indication of something going wrong. Amps would show but its hard to tell.
Cheers
AP

discopotato03 · Post by **discopotato03** » Tue Nov 17, 2009 2:09 pm

Most go with Voltmeters because of the complexity of having an everything pass through type amp meter .
The thing with volt meters is they don't tell you a whole lot when there's no load on the battery . Like AP said significant over volt or low voltage stands out well enough on a decent volt meter .

Back in the early mid 80's I had an amp meter go open circuit in a Mini meaning everything went dead . Pretty simple to bridge the cables together to power up the system but a worry if you don't realise what happened .
This morning I did a search on wiring up amp meters and those in the know are pretty quick to tell you about the sort of current running through that gauge and the dangers of failed insulation and major shorting of the battery .

For the sake of reliability and simplicity I'd opt for the volt meter , it should show 14.4-14.7 volts in a healthy system and more or less in an unhealthy one .

A little OT but related I've just replaced my dying 370 CCA Century battery with a 570 CCA Century because this is the only way you'll get any distance in an EFI car if the alternator stops charging .
I'd go the more than adequate battery and rebuild your alternator every few years (bearings and brushes) and think about a volt meter last .

Cheers A .

Bert · Post by **Bert** » Tue Nov 17, 2009 4:39 pm

Amp meter doesn't need to go in the main charging circuit per se, just hook up in parallell, so if the meter dies no problems with the rest of the electrics, though working out the shunts can be a bit of a pain

steptoe · Post by **steptoe** » Tue Nov 17, 2009 5:44 pm

thanks, was thinking Volts, understands them bit better than amps. As for the bigger battery I stick the Falcon battery in all my Subies so I can alternate , or swap between either cars. Those litle batteries...phhht

YouTube · Post by **El_Freddo** » Thu Nov 19, 2009 5:12 pm

Agreed about the little battery! I use a 550CC or something of the like, overkill when you compare the factory specs but I'm all for it!

As for the Amps guage - I thought it couldn't be set in parallel as it would allow current to flow through a bypass around the amps guage and not give an accurate reading. I've got one in my subi but its yet to be hooked up as I'm still trying to work it out. I think I'll wire it between the alternator and the battery/fusable link box to see what the alternator is doing (charge/discharge). I think that's right(?).

Both would be the best way to go as you'll have more info on hand immediately. The subi's have a volt guage on the sports dashs as you'd know, I agree with previous posts about the telling of the condition of the battery and is a good all rounder, but if you want to know what the system is using at that point in time the amp guage would be best.

Cheers

Bennie

steptoe · Post by **steptoe** » Fri Nov 20, 2009 9:12 am

both would be a good idea. The joint in the US don't have either in stock. I was gonna order some LPG gear and saw other bits on their website but nil stock now. $6 for a gauge then turned into 9.50 also. No hour meters in stock, no altimeter either! Found another place selling off old stock LPG and have ordered with them. Bennie, it is only small package, you wanna pick it up on your way through??

YouTube · Post by **El_Freddo** » Fri Nov 20, 2009 12:07 pm

Hehehe... unless its on the way to the airport there's not much chance of that happening steptoe! Unless you can get it sent to the hotel I'm at in Anahiem and its under 23kg

Cheers

Bennie

Bert · Post by **Bert** » Fri Nov 20, 2009 3:22 pm

El_Freddo wrote: As for the Amps guage - I thought it couldn't be set in parallel as it would allow current to flow through a bypass around the amps guage and not give an accurate reading. I've got one in my subi but its yet to be hooked up as I'm still trying to work it out. I think I'll wire it between the alternator and the battery/fusable link box to see what the alternator is doing (charge/discharge). I think that's right(?).

Both would be the best way to go as you'll have more info on hand immediately. The subi's have a volt guage on the sports dashs as you'd know, I agree with previous posts about the telling of the condition of the battery and is a good all rounder, but if you want to know what the system is using at that point in time the amp guage would be best.

Cheers

Bennie

A percentage of the current passes through the amp meter which involves the shunt, got the formula for calculating it somewhere but all said and done I still prefer a voltmeter, easier to hook up for starters and agree with Bennie if you want to know what the alternator is doing at any given time the amp meter is the way to go. Oh and they both reference the alternator not the battery, battery only used when engine isn't running or alty is dead.
Cheers
Bert

wrxer · Post by **wrxer** » Mon Nov 23, 2009 9:11 pm

volts for me too.
stuff having that fat power cable running into the cabin through some nonedescript guage, only to turn around and run straight out again. but surely now you can get inductive ones that clip onto power wire, i mean you can get inductive multimeters that work fine

tony · Post by **tony** » Tue Nov 24, 2009 12:49 am

I would go for an ampmeter every time. you can do most of the stuff the volt meter does, except maybe the standing charge in the battery.
if the fan belt breaks the amp will show discharge, if the alternator is not working it will show discharge, if the alternator goes faulty and overcharges the meter will show it as the charge rate will be excessive for a long period so you will be able to avoid cooking the battery, if you get a short circuit the ammeter will show it, if the appliance overloads the system and draws more than the alternator can supply or the alternator is running down, (radio, spotlights, etc) the ammeter will show it, you can work out the current draw of each item by using the ammeter, if you are having a problem with the battery running flat overnight you can see from the ammeter if there is an unusual discharge.
however it is important that you use sufficiently thick cables and proper soldered terminals to handle the current. if a cable is getting warm it is too small.

tex · Post by **tex** » Tue Nov 24, 2009 10:53 am

Unfortunately the inductive loop only works on AC current so it is not ideal for an automotive purpose unless you have an external regulator (I haven't seen one mounted outside the alternator on a subaru yet)! what you could do though is remotely mount the shunt resistors for example conveniently under the bonnet, Although you will still need big cables and need to account for resistance in the cable. Biggest thing is make sure it is all double insulated (a friend nearly burnt down her boat on the weekend after failing to do this)!