I recently got 1973 Plymouth Valiant with a 318. It died while driving about a month ago. I jumped it and got home but it seemed like it wasn't getting charge. I replaced the battery, alternator, and voltage regulator but now I'm noticing that the ammeter / alternator gauge starts to max out upon accelaration. The ammeter needle is around the middle upon startup and for the first few minutes or so but once the electric fans kicks on the ammeter shoots up and maxes out with any acceleration. It hovers to the right at idle, but jumps to 40 with any gas. If I turn on the headlights, it jumps a bit higher at idle too. The voltage regulator feels hot but to be fair its been really hot out. The previous owner made a mess of the wiring so it's hard to pin point the problem. I'm assuming its not safe to drive like this and I'm at risk of melting something, but I'm not sure where to start. Any tips would be great
Ammeter Maxed
- Thread starter Valiant73
- Start date
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Try a new voltage regulator?
First of all, is it really overcharging or dod your ammeter go on the fritz? You need to start with a volt meter at the battery. 14.2 volts is a healthy charging system. Much more than that can cause battery boiling and burned out light bulbs and possibly a electrical fire if you have a dead short.
67Dart273
Well-Known Member
I'm thinking that WHEN YOU WIRED IN THE electric fans you got them wired in such a way that the ammeter no longer reads correctly
"Electrically speaking" the alternator output and all accessories/ loads connect to one side of the ammeter, and ONLY the battery connects to the other side.
To put this more practically, if you hook something a large load to the battery or to the starter relay "big stud" the ammeter will no longer read properly
ALSO if you are running "big fans" and have a stock unmodified ammeter circuit YOU NEED TO READ THIS ARTICLE and do a bypass
Catalog
Many on here don't agree with how that article bypass is done, and you can use a bypass wire from the alternator output to the battery BUT YOU MUST protect it or breaker it
Toomanmike is right----------you need to monitor battery/ system voltage at the battery AFTER THE BATTERY is warmed and "normalized" and see what the system voltage actually runs for voltage. You want no lower than 13.5 or so and no higher than 15 or so. "Normal warm" is 13.8---14.2
ANOTHER issue is that the voltage regulator may not be getting 'full' battery voltage at the IGN terminal of the VR which is the sensing.
"Electrically speaking" the alternator output and all accessories/ loads connect to one side of the ammeter, and ONLY the battery connects to the other side.
To put this more practically, if you hook something a large load to the battery or to the starter relay "big stud" the ammeter will no longer read properly
ALSO if you are running "big fans" and have a stock unmodified ammeter circuit YOU NEED TO READ THIS ARTICLE and do a bypass
Catalog
Many on here don't agree with how that article bypass is done, and you can use a bypass wire from the alternator output to the battery BUT YOU MUST protect it or breaker it
Toomanmike is right----------you need to monitor battery/ system voltage at the battery AFTER THE BATTERY is warmed and "normalized" and see what the system voltage actually runs for voltage. You want no lower than 13.5 or so and no higher than 15 or so. "Normal warm" is 13.8---14.2
ANOTHER issue is that the voltage regulator may not be getting 'full' battery voltage at the IGN terminal of the VR which is the sensing.
Early a body
Well-Known Member
go but an voltmeter gauge and see what you are really running, My 65 cuda always is on the high side on the gauge but reads 14.2 at the battery and on the voltmeter i installed. So the gauge in the dash is likely the problem.
I justed tested it. At the battery was 13.3 while running. Increasing the rpm brought it up a little, but it still stayed below 13.5. Once the fan kicked on, it dropped to 12.7 and increasing the rpm didn't change the reading. The ammeter was still reading high and would max out with an rpm increase.
When I installed the alternator and voltage regulator last week, it was reading 14.5 at the battery while idling. With a brand new alternator and regulator, what esle could be causing this?
When I installed the alternator and voltage regulator last week, it was reading 14.5 at the battery while idling. With a brand new alternator and regulator, what esle could be causing this?
Professor Fate
Push the button, Max...
Here we go... you are operating under the assumption that "new=good". It doesn't. Personally, I've been averaging 50/50 with common parts store regulators and reman alternators. If you still have your old regulator, try swapping that back on (making sure it is well grounded) and see what happens.
And you never did say where or how you wired in your fans...
And you never did say where or how you wired in your fans...
That may have been because there were no loads on the alternator and now...
There are additional loads, one of which could be the battery is discharged and/or other possibilities.
You're investigation will require figuring some more things out.
One is easy. Measure the voltage across the battery with the key off. See if its near 12.8 V
Two things. Lets deal with this one here. With the fan on, and the battery charging te alternator is maxed out idle rpm.
If the ammeter is reading high at idle, nothing else running, that means the battery is charging.
Then on top of that, you see it increase toward charge when the fans kick on. This means the fan was wired to the battery.
Fix this right away. Move the fan power to the alternator output. This may not be the permanent solutionb but will get past the danger of abusing the battery feed.
This was already described in the begining of post #4. I'll just illustrate it.
(aside: Honestly unless there is a good reason to keep the electric fan, the best option is to switch back to mechanical with a shroud.)
Here's a schematic of the alternator and battery wires.
See where the ammeter is located in the wiring?
and
See where the fusible link is located in the wiring?
It works like this:
When the alternator is not working and something needs power, it comes from the battery.
The ammeter shows the current flowing out from the power supply (battery at something around 12 Volts)
When the alternator is running, and the battery needs charging, it draws from the alternator.
The ammeter shows the current flowing from the alternator, producing power around 14 Volts if it can, to the battery.
When the battery is charged, no current flows through the ammeter.
That circuit was not intended to be carrying current all the time.
Attaching the power for the fans to the battery is a commonly done, but its a mistake. It stresses all the connections between the alternator output terminal and the battery. As they carry greater amounts of current than intended, for longer periods of time, they get hot. That makes them worse connections, and the situation only gets worse.
So the quick solution is connect the fan power to the alternator, and don't run it when the engine is off.
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If you find voltage is climbing with rpm, then either the regulator is not doing its job, or its getting the wrong infomation.
Measure the votlage at the alternator output and compare to the votlage at the regulator input (blue ignition wire at field or ballast resistor).
Couldn't agree more!
67Dart273
Well-Known Member
A few things about the alternator voltage dropping
1..First forget the ammeter reading. As I told you earlier you have the fans and possibly other loads wired "on the wrong side" of the ammeter
2...It may be that you have serious voltage drop in the "ignition run" circuit which feeds both the alternator field and the VR. When this drop is not too much, it actually causes OVER voltage. But you may have a more serious drop, OR you may have added stuff to that circuit causing the same problem.
3...The other thing that can cause this, or it could be a combo of 2 and 3, is that the alternator simply is too small to output enough amperage to keep things "up." Add up pumps, fans, whatever is running, AND if the battery is somewhat low. it may be the alternator is too small OR THE alternator may have something wrong with it such as a bad diode that partially reduces the output OR THE alternator may have been mis-labled and is not the output rating you believe it to be
4...To find out if the alternator is large enough and is working at that rating, disconnect both field wires from the alternator. Get some no14 wire and appropriate connectors and "rig" the field to ground either field terminal and wire the other field direct to the battery with a GOOD connection. Do not power this until you are ready to test.
Now monitor battery voltage and also get in your mind to also check the alternator output stud, those two points. Get the car running, hook up your field "rig" and monitor battery voltage and modulate engine RPM to keep voltage below 16. With EVERYTHING running and with the engine running to simulate "low to medium cruise" RPM check that battery voltage is up to at least 13.2 or higher. IF NOT check the alternator stud and see if that reading is a lot higher. If it is more than 1 or 2 V difference, you have a SERIOUS drop problem in the wiring between alternator and battery---that being the bulkhead connector, the ammeter, and so on
5...If the above checks out OK, now wire up everything "normal" except "rig" the branch at the ballast (or where it was) so you can jumper direct battery power into that circuit. This will eliminate voltage drop from the ignition "run" circuit. Jumper power into that from the battery and again see by battery V if the system will keep up. If (4) checked out OK and test (5) checks out OK you likely have a serious voltage drop from battery--through bulkhead--through ignition switch--back out through bulkhead--and to the IGN1 "run" circuit feeding the field and the VR IGN terminal.
1..First forget the ammeter reading. As I told you earlier you have the fans and possibly other loads wired "on the wrong side" of the ammeter
2...It may be that you have serious voltage drop in the "ignition run" circuit which feeds both the alternator field and the VR. When this drop is not too much, it actually causes OVER voltage. But you may have a more serious drop, OR you may have added stuff to that circuit causing the same problem.
3...The other thing that can cause this, or it could be a combo of 2 and 3, is that the alternator simply is too small to output enough amperage to keep things "up." Add up pumps, fans, whatever is running, AND if the battery is somewhat low. it may be the alternator is too small OR THE alternator may have something wrong with it such as a bad diode that partially reduces the output OR THE alternator may have been mis-labled and is not the output rating you believe it to be
4...To find out if the alternator is large enough and is working at that rating, disconnect both field wires from the alternator. Get some no14 wire and appropriate connectors and "rig" the field to ground either field terminal and wire the other field direct to the battery with a GOOD connection. Do not power this until you are ready to test.
Now monitor battery voltage and also get in your mind to also check the alternator output stud, those two points. Get the car running, hook up your field "rig" and monitor battery voltage and modulate engine RPM to keep voltage below 16. With EVERYTHING running and with the engine running to simulate "low to medium cruise" RPM check that battery voltage is up to at least 13.2 or higher. IF NOT check the alternator stud and see if that reading is a lot higher. If it is more than 1 or 2 V difference, you have a SERIOUS drop problem in the wiring between alternator and battery---that being the bulkhead connector, the ammeter, and so on
5...If the above checks out OK, now wire up everything "normal" except "rig" the branch at the ballast (or where it was) so you can jumper direct battery power into that circuit. This will eliminate voltage drop from the ignition "run" circuit. Jumper power into that from the battery and again see by battery V if the system will keep up. If (4) checked out OK and test (5) checks out OK you likely have a serious voltage drop from battery--through bulkhead--through ignition switch--back out through bulkhead--and to the IGN1 "run" circuit feeding the field and the VR IGN terminal.
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Ditto. The mechanical fan is a power loss. Perhaps 15 HP or so. But it is however an excellent cooling device when properly set up with a proper fan shroud. The radiator must also be in good shape for ether so that’s a non discussion when it works well and sized right.
The factory fan or the MP viscous fan (even better) in a shroud will cool a lot of HP. It’s worth the power loss in most cases. There also very very reliable.
Early a body
Well-Known Member
I have run into this before. To fix this I had to do 2 things. I ran an wire from the positive on the alternator to the starter relay. The battery connection is also at the starter relay so it will provide a direct link to the battery. Second I installed a larger field wire- the one that goes to the ballast resistor- that seemed to solve my problem
This is assuming that you had 14.5 when you installed the new alternator. I have found most alternators you can buy from local parts houses are not as good as they once were. I have been upgrading to powermaster alternators when the ones I am running stop working. i have had a power master on one of my cars for over 10 years and still no problems
512Stroker
We are all here because we are not all there.
When I ran electric fans I always wired them direct off the battery with a relay and a temperature sensor so the fans did not pull off the rest of the electrical system.
2 things
As others have said your battery voltage is to low. This is a must repair, dont blow it off or you will have issues.
Bypass the ammeter and get a volt meter.
But now surely you understand that the battery only supplies power when the alternator can't. So it is not the direct source of power when the engine is running.
512Stroker
We are all here because we are not all there.
True I do understand that the battery is not the source while the engine is running.
I always ran a service switch for the fans so I could operate the fan without the engine running. It was an simple and effective way to add a fan circuit.
to start with, once the engine is dead cold, I would suggest that you disconnect the electric fan, start the car and see what it does. That should easily isolate the issue if it has to do with how the fan is wired.
66 Valiant wagon
Well-Known Member
I recently had a similar situation. It was a parts store voltage regulator. Good luck.
First off, you need a real alternator that can generate the necessary amps to run your fans. The crappy mopar alternators aren’t capable of doing this properly. Even the high amp ones don’t supply clean, ample current at idle.
Once you install a proper unit, add a good size charge cable to go from the alternator to the starter relay. This creates a path of less resistance for current to travel. Doing this eliminates the need to hack out your ammeter.
Depending on your engine the Nippondenso or GM cs130s are good choices.
Once you install a proper unit, add a good size charge cable to go from the alternator to the starter relay. This creates a path of less resistance for current to travel. Doing this eliminates the need to hack out your ammeter.
Depending on your engine the Nippondenso or GM cs130s are good choices.
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