Another ammeter question

Oliver 1655 diesel. 12 volt system in parallel two batteries.

Have been monkeying with electrical system to get it working right.

So far so good.

Idiot light installed, alternator charging battery after start, ammeter comes back to just above 0 after a few minutes.

Manifold heater is the question.

Thought it wasn t working, as pressing button makes solenoid click but no draw on ammeter while holding button.

However it sure feels nice and hot to touch after a long 30 second press.

Any ideas why a large load like that wouldn t show up on ammeter?

Battery goes to starter, starter goes to ammeter, starter goes to manifold heater.

Flick on headlamps and that shows a draw on ammeter (engine off)

Press heater button nothing shows.

Lights go through ignition and ignition powered thru ammeter

I prob don t understand electricity.

I assumed if the heater pulled juice from battery by way of starter post, that would show up on ammeter.

As ammeter is wired on one side to starter post as well..

However perhaps the manifold heater bypasses the ammeter? Does it just suck juice from battery to starter post to heater and the ammeter would have no way of knowing current was flowing from Battery.

Sorry long winded. Thanks again.

By your description it doesn't sound like the heater is wired through the ammeter. The ammeter will only show load
that is fed trough it in series.

Ammeters just aren't sensitive enough to read small changes. Car manufacturers
switched to volt meters a long time ago. When I change one I install a volt
meter.

You answered your question, the heaters do not pass a load through the amp meter.

Probably wired that way intentionally as the heaters draw a heavy current, more than the amp meter can handle.

In order for the ammeter to register the current draw for the heater, it would have to be connected on the other
side of the ammeter. As it is, it bypasses the ammeter.

In general, heavy current items like manifold heaters, starters, and glow plugs are not routed through the ammeter.
They might have enough current draw to damage the ammeter. In any case, they would probably be beyond the ammeter's
ability to register.

I see what ur sayin. I agree after asking the question. Seems like it s not wired through.

Thx

Not all have voltmeters.
my 2005 buick has a idiot light
My 2007 GMC truck has a voltmeter.
My 2018 cadillac has both idiot light and
you can access a digital voltmeter on the screen if you know how to use the menu to display the digital voltmeter.

My preference on old tractors is an ammeter and an idiot light..
An idiot light tells you the voltage is above the battery voltage.. My Jubilee idiot light goes off after I start it.
I have to wake up the alternator by revving the engine over 1500 rpms and then the ammeter will show a charge at any speed.

It doesn't make sense to route the manifold heater through the ammeter, since you wouldn't use it while the motor is running. The purpose of the ammeter is to tell you if the charging system is working, and of course the generator isn't running when the engine is stopped. On the other hand, you DO use the headlights when the engine is running, and it's important to know if you're getting a net charge with the headlights on, so they're wired through the ammeter.

It would be nice to get some positive feedback that the heater is actually working when you hit the button, but the engineer who designed the system probably opted to wire it as directly to the battery as possible to reduce voltage drop. You say it's connected to a 'starter post', I'm guessing that post is actually on the starter solenoid and is wired directly to the battery as well as to the ammeter and manifold heater switch/relay.

Good morning 777, BY DESIGN high currents such as what a starter draws or possibly manifold heaters or
glow plugs (if so equipped and designed that way) DO NOT PASS THROUGH THE AMMETER. The way a typical
ammeter operates is:

SUPPLY SIDE wires to the battery so selected loads (lights ignition accessories etc) receive power and
often the BATTERY is the ONLY thing wired to the SUPPLY SIDE of an ammeter. Often instead of the ammeters
SUPPLY side being connected direct to the battery, it wires to the INPUT side of a starter solenoid or
switch where the big battery cable attaches.

LOAD SIDE feeds low current (NOT starter or heaters or glow plugs possibly??) to accessories, lights,
ignition etc PLUS the output of a generator or alternator

SOOOOOOOOOOO YESSSSSSSSSSS based on how it was designed and wired ?? high current devices like manifold
heaters or glow plugs would NOT show up on the ammeter.

The ammeter will register and indicate the + charging current INTO the battery or the - discharging
current OUT OF the battery.

If a good charging system is working at fast RPM battery voltage should rise to at least 13 up to 14 or
so SUBJECT TO BATTERY AND VOLTAGE REGULATION. If it never rises shes NOT charging or else its 100% charged
and/or the voltage regulation system causes such

To see if depressing the heater button sends voltage to the heater, place a volt meter or test lamp on
the heater input and see if voltage goes from zero to 12 when depressed. With a heater solenoid button
depression activates the solenoid causing a click and closing the circuit so the heater receives power
REGARDLESS if any current is shown on the ammeter if the heater circuit DOES NOT pass through it. Thats an
easy test with a meter or test lamp.. IM NOT SURPRISED if a heater does NOT pass its current through the
ammeter

Perhaps AND I SUSPECT the manifold heater via its solenoid receives its power off the starter solenoid
INPUT which is connected to the battery via that huge cable !!! If so its current draw DOES NOT pass
through the ammeter...

Best wishes to you and all here, hope this helps, post back any questions

John T

John,

It really isn't necessary to measure the voltage at the manifold heater input because as Sellener says However it sure feels nice and hot to the touch after a long 30 second press. That means the manifold heater is working.

In regard to this ammeter topic, think about the ratio of starter, manifold heater and other heavy current loads as related to the smaller current loads. This ratio is large and if the ammeter was designed to read all of these, the smaller currents most likely wouldn't even register on such an ammeter. The heavy loads are quite short, time wise, which again wouldn't be very useful. I hope you understand the drift on my thoughts here, no offense meant! Ron

(quoted from post at 07:27:30 07/08/22)

[b:29e2dfc2f5]It would be nice to get some positive feedback that the heater is actually working when you hit the button[/b:29e2dfc2f5],

Click to expand...

[b:29e2dfc2f5]"However it sure feels nice and hot to touch after a long 30 second press."[/b:29e2dfc2f5]


That sounds to me like it is working.



This post was edited by Carlmac 369 on 07/08/2022 at 07:54 am.

IH put an ammeter on their glow plugs for the D282. Nothing saying the same thing can't be done for the Oliver grid heater.