Ammeter was sitting at 0, now peaks when revved, but...

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G

Gruntled

10 Year
Joined
May 31, 2011
Threads
10
Messages
188
Location
Darwin, Australia
Hi All,
My ammeter in the dash has always sat at 0 during driving or whatever. Over the past few days it has begun jumping up to +30 when I rev the engine. However, it then settles back down to 0 after a few minutes of holding the revs up a little (that is, revving about 1500-2000 rpm).

Any ideas what I should be looking at to begin diagnosis? Altometer bushings? :confused:
Thanks!
Scott
 
Year of your rig would help. On earlier 40s, the ammeter was much more sensitive. When they switched to the shunted ammeter, it became much less useful.

Think of your ammeter as a device to show you where current is going. If it is to the positive side, electricity is flowing into your battery. At 0, batteries are fully charged and alternator is keeping up with demand. If the meter deflects to negative, electricity is flowing out of your battery to power things (lights, accessories, etc).

Did your ammeter work before, meaning it would deflect to negative with the key on, engine off and then switch to slightly positive with engine running? If so, I would guess something is drawing down the batteries while the key is off. Try and find a short or something.

If your ammeter never really worked all that well (especially in a newer model), then look at your fusible links. Tom (i.e. Lostmarbles) has a good write up on his fusible links causing his ammeter to jump around.

Good luck!

:cheers:
 
FF LC FREAK said:
Ammeter doesn't care about voltage. It only shows your electrical flow.
Click to expand...

are you running a generator with a mechanical voltage regulator? if so the voltage reg will control when the generator motors to charge and when it stops based on armature amps. The voltage regulator regulates the charging circuit.

It may differ for an alternator somewhat however, I am no pro in that boat, but very likely simular.

let us know your set up and someone that knows your configuration can pipe in.

I think a good sign is that you amp gauge is not showing a drain though, meaning you are not charging and having a draw.
 
Thanks guys. The FJ is a 1977. The ammeter was previously sitting at 0 all of the time - it would not deflect to negative when the ignition was switched on, rather it would go straight to 0 and sit there regardless of what I did - driving, idling, lights on, lights off etc. It has always moved a little back and forth in time with the indicators.

The strange thing is that it has never shown a positive before, and now when the engine is cold or I have been idling for a while and accelerate quickly the needle jumps up to positive, and then goes back to 0 at idle. This is not consistent though - sometimes it will start jumping around up to positive then back to 0 when I am driving along. If I accelerate slowly, the needle stays at 0. For most of the time (80%) the needle is remaining steady at zero during my daily 1 hour drive to work and back, and behaves as it always has.
 
I suggest you check battery condition - how many volts the regulator is sending to it using a digital voltage meter.
I think it should be 13.7 v max or so.
I installed a new voltage regulator purchased from a Toyota unathorized dealer and thought nothing of it.
It sure looked genuine, packaging and all.
The first indication something was wrong was when my Sony Explode radio cut out when I first headed out down the road.
Apparantly, they have a built in shut down for when the voltage supply is too much.
The radio would kick back in after 5 or 10 minutes.
Then, on a highway trip, my battery fried - it was steaming (literally) hot.
Had to replace that battery to get going again.

It looks like I didn't get a genuine Toyota regulator, but I sure will next time around.
 
Gruntled said:
The ammeter was previously sitting at 0 all of the time - it would not deflect to negative when the ignition was switched on, rather it would go straight to 0 and sit there regardless of what I did - driving, idling, lights on, lights off etc. It has always moved a little back and forth in time with the indicators.
.
Click to expand...

This is normal behavior when everything is fine. When it deflects left and stays there, the charging system isn't keeping up with demand and your battery is discharging. When it deflects right and stays there for some time, the battery is discharged and it charging. When it is charged, it comes back to zero.
 
FF LC FREAK said:
......
If your ammeter never really worked all that well (especially in a newer model), then look at your fusible links. Tom (i.e. Lostmarbles) has a good write up on his fusible links causing his ammeter to jump around......
Click to expand...

Gruntled said:
Thanks guys. The FJ is a 1977. The ammeter was previously sitting at 0 all of the time - it would not deflect to negative when the ignition was switched on, rather it would go straight to 0 and sit there regardless of what I did - driving, idling, lights on, lights off etc. It has always moved a little back and forth in time with the indicators.

The strange thing is that it has never shown a positive before, and now when the engine is cold or I have been idling for a while and accelerate quickly the needle jumps up to positive, and then goes back to 0 at idle. This is not consistent though - sometimes it will start jumping around up to positive then back to 0 when I am driving along. If I accelerate slowly, the needle stays at 0. For most of the time (80%) the needle is remaining steady at zero during my daily 1 hour drive to work and back, and behaves as it always has.
Click to expand...

Gruntled said:
Ah ha! Having read through Lostmarbles fusible link thread I am very suspicious of mine! Hopefully Coolerman still sells replacements!!
Click to expand...

Hi there Gruntled.

I was going to post up suggesting your "fusible link" but didn't because I thought Toyota hadn't yet started using a fusible link as the ammeter-shunt in 1977.

Do you have those two 5A ammeter fuses in the loom near your battery's 12V +Ve post? If you do, that'll prove you do indeed have the fusible-link-shunt-type ammeter. (And in which case, I'd agree that the link is likely to have frayed/deteriorated from vibration, reducing its effective cross-sectional area, and thereby magnifying the previously undetectable ammeter-needle movements.)

Whatever the cause, your symptoms are certainly the same as those I had from my fusible-link fault.

And if you do have the same type of ammeter as me and if you find it is the same fusible link problem - then I suggest doing your own repair.

Rudi has a good thread on making his own fusible link here:
https://forum.ih8mud.com/diesel-tech-24-volts-systems/526232-fusible-link-one-my-78-bj40.html

:cheers:
PS - The only thing special about "fusible link wire" is the "insulation material" and the value of having it non-combustible is probably over-rated anyway.

(If your fusible link isn't close to other combustible material, I think you'd be fine using wire with ordinary combustible insulation provided it is shrouded in a "non-combustible fabric-sleeve" like the original Toyota ones were.)
 
OK, more issues - the ammeter is still jumping around and I don't have a fusible link, but another fault has arisen. My fuse on the coil circuit blew a couple of days ago, and the fuse kept blowing as soon as the ignition was switched on. Today we traced the wiring on that circuit and found nothing awry. We then replace3d the fuse again, and it didn't blow. I must have an intermittent short somewhere in the system? Any advice on where to go from here would be very, very much appreciated. Is it time to visit an auto electrician? Thanks!!
 
The ballast resistor for the coil faulty or tired?
 
Cheers Crumbo, I replaced the coil with one I had sitting around and the fuse was still blowing. I suspect a short somewhere, but it's gone away now which is a pain since I can't find what's wrong! I suspect the alternator but I am not sure if it could cause the problem with blowing the fuse if it is spiking? I had the coil fuse blow a few months back and suspected the idle solenoid, but that seems all good.
 
Gruntled said:
Cheers Crumbo, I replaced the coil with one I had sitting around and the fuse was still blowing. I suspect a short somewhere, but it's gone away now which is a pain since I can't find what's wrong! I suspect the alternator but I am not sure if it could cause the problem with blowing the fuse if it is spiking? I had the coil fuse blow a few months back and suspected the idle solenoid, but that seems all good.
Click to expand...


Is your regulator on the firewall...try starting it without that pluged in and see how you go
 
Hi all, I made a video this afternoon to show how your AMP gauge should behave / work.
The first question is; which AMP gauge do you have?
This one ? amp.webp This is the one for '73 till end '78 and has an internal shunt, which means the full current runs from the battery/alternator through the firewall passing this gauge.
Or this one? amp50.webp This one is for '79 and later and has an external shunt. It's actually a milliVolt meter that reads the voltage drop over the 2 fusible links under the hood.
The video I made is from my '78 BJ40 and should be equal to your "77 FJ40. If your AMP gauge acts like the one in my video then I can only say; your needle was stuck and came free.

If its acting different try to describe what happens compared to mine.
Note that the battery voltage is 12.5V before I crank the engine.
While cranking the Voltage drops to 9.4V.
At idle the Voltage is back at 12.5.
When I rev the engine you'll see the AMP gauge reading 15 Amps and the Voltage is slowly climbing to a bit over 14.4 which is the "set point" of my Voltage Regulator. From that moment the VR tells the Alt to stop charging. The battery is full. The battery doesn't hold the charge at 14.4V but drops back a bit which the VR "sees" and tells the Alt to charge again. This is the shaking of the needle that you see. Charge - no charge, Alternator on - off - on - off and so on. This process goes faster with the rpm's going up and is normal behavior for these "old school" Voltage Regulators. It knows only 2 situations, on and off. So it's the switching from the VR that you see in your AMP gauge.
The microphone of my brand new camera is very sensitive so keep your hand at the volume knob after I finished speaking. I had the door open while recording and the sound from the engine sounds terrible. Well the engine sounds good but the recording sounds bad.
Here is the video: amp_gauge-1.AVI - YouTube
There is a 2nd video to show what you see when you discharge the battery by using your headlights, brake and turn signals. amp_gauge_2.AVI - YouTube

Hope this helps a bit in understanding the Amp gauges in our trucks.

Rudi

EDIT: I recently found out that the OEM regulators have 3 steps: full charge (Bat. low), half charge (Bat. almost full) and no charge (Bat. full). The excessive shaking from my ammeter in the video is caused by my "solid state" 2 step Bosch Voltage Regulator. Just; Charge - No Charge.
amp.webp
amp50.webp
 
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Hi Rudi,
Thanks very much! My ammeter is behaving just as you describe - the videos are most helpful. Here is a quick video of what my ammeter is doing:
Ammeter behaviour 1977 FJ40 - YouTube

I suppose my ammeter needle must have been stuck as you suggest?

Crumbo, I'll check into the regulator. IS that the box sitting on the upper passenger side of the firewall wired to the alternator?
Cheers,
Scott
 
Gruntled said:
Hi Rudi,
Thanks very much! My ammeter is behaving just as you describe - the videos are most helpful. Here is a quick video of what my ammeter is doing:
Ammeter behaviour 1977 FJ40 - YouTube

I suppose my ammeter needle must have been stuck as you suggest?

Crumbo, I'll check into the regulator. IS that the box sitting on the upper passenger side of the firewall wired to the alternator?
Cheers,
Scott
Click to expand...

Hi Scott,

Good video. Looks fine to me. Just for the peace of mind check with a voltmeter if your amps are going down (= battery is full) at a voltage somewhere between 13.8 and 14.4 Volts. This voltage "set point" depends on your Voltage Regulator but any value between those 2 numbers is fine. The reading while driving (= more then 1000rpm) when the battery is fully charged is something between 5 - 10 amps. This depends on the state of the battery. Low if the battery is new and a bit higher when the battery is a few years old.

Happy driving !

Rudi

Ps. before you start diving into the VR just do a voltage check. No need to open things when there is no reason for it.
 
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I had a bad voltage regulator years ago. Amp guage would jump around, usually to positive just driving down the road then back to 0, but it would be very eratic, just bouncing and jumping around, would even exibit fluctuations in the lights and heater blower speed at constant cruisng RPM's, unlike when you stop at a stop light or something and the lights and heaters slow. Eventually it started jumping to the negative too. Replaced the alternator not knowing the VR was the problem. Still had issues, replaced the VR with a Toyota rebuilt unit, still had issues. Fianlly took it to a auto electrical place. They put in a generic Ford VR that was solid state (electronic) and I never had another issue ever with charging, now ammeter shows the proper negative deflection when starting and a slight positive most the rest of the time.

While the VR controls voltage, it also controls charging flow. My original VR was probably just old, I think the rebuilt replacement had sat on Spectors shelves for so long the points were coroded in it. They use two sets of points that open and close fairly rapidly to control voltage. A bad ground to the VR regulator case can have bad effects too, I'm seeing that right now on an old IH dumptruck. Truck shows a discharge, when I bump the VR which is under the dash, I get charge, it is a new VR, so I think the old rusty truck body is not grounding it very good.

You can open it and dress the points with a points file, there are specs in the factory manuals as I recall for proper operation of the unit.

I'm sold on the electronic ones and Transpro sells a factory replacement version for Cruisers. They look identical to stock but no more points in them. Otherwise the one in mine is just a VR from a 70's to 80's ford, Transpro brand also. The terminals are marked on it, you have to match I and F to the alternator, the wiring digrams label these wires for the cruiser. I cut the pigtail off a bad VR and spliced it to the flat plug on my new VR so that it plugged in properly to the Toyota loom.

The VR is mounted as you describe on your Aussy cruiser I believe, for us US guys it is on the drivers side below the brake and clutch masters, half way up the firewall. Small black box, rounded edges with gold zinc base, two bolts hold it on, on one side. Usually a three hole plug.
 
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