Mopar Muscle Association UK

My 1970 318ci Satellite has developed a charging problem over the winter!
I have read a few posts on here but none the wiser!!
Put car away early October and not used it until xmas week for a 10 mile round trip which i noticed Amp gauge being on the negative side, put that down to taking a while to start after sitting about a few months and topping battery up! So this Saturday changed regulator for a new black Mopar one ( instead of grey ching chong one, just didn't like the look of it). Checked voltage while running 12.8v, changed back to old regulator (ching chong) 12.8v! This is reading on battery and alternator?
Took a chance and done a round trip of 220 mile yesterday (Sunday), Amp gauge was always negative, just a bit with nothing on and right down low with lights, wiper and heater running. Stopped started 6-7 times on trip. Stopped and checked voltage a hour from home 12.3v, Run last hour home with lights on, checked voltage when home with engine running and it was 11.5 volts!!
So its not charging but i would expect it to be flat flat and not even run after 4 hours run time?
So is it Regulator or Alternator? How do i do the test with the field wire shorted out? need more detail on that before i attempt it please! Someone mentioned bin it and get a single wire?
Cheers Rich

The 12.8v (and less) you are seeing is the Battery voltage.
Should be charging at 14.6v so it points to either the Alternator itself, or wiring (or both!!) - or the real killer is that a fault has killed both regulators you have tried.

If you know what you are doing you can hot wire the battery to the field windings very briefly whilst the car is running and measure the Alternator output voltage - It should be huge by comparison, so only do it VERY briefly.

Failing that, you will have to try a different Alternator if there is nothing obviously wrong with the wiring.

Pete wrote:The 12.8v (and less) you are seeing is the Battery voltage.
Should be charging at 14.6v so it points to either the Alternator itself, or wiring (or both!!) - or the real killer is that a fault has killed both regulators you have tried.

If you know what you are doing you can hot wire the battery to the field windings very briefly whilst the car is running and measure the Alternator output voltage - It should be huge by comparison, so only do it VERY briefly.

Failing that, you will have to try a different Alternator if there is nothing obviously wrong with the wiring.

Cheers Pete, i presumed the voltage i was getting was just battery voltage, but it must be getting some sort of charge to last that long on the trip??
I've got a 12v electrical probe tester, so i can easily put 12v from battery to alternator. But which field winding do i put it on?

It depends on your set up.

Pre '70 had a single field terminal (the other to Earth) and later ones have a twin feed from the Regulator.

Pete wrote:It depends on your set up.

Pre '70 had a single field terminal (the other to Earth) and later ones have a twin feed from the Regulator.

Mines a 70 with 2 field wires on back of altetnator!

You could earth one of them and then VERY Briefly connect a direct 12v supply to the other. I take no responsibility in the outcome, but my guess is (if you have ruled out any wiring issues) that the Alternator is kippered.

some people change the alternator and regulator at the same time as it has been known for one to fail and damage the other and you end up in a vicious cycle.

Cheers Pete, think I'll just go for a replacement now. Just got to decide if to go one wire or not! Any recommendations who can supply either?
Cheers Rich

Hello Rich,
I had this problem with my 67 (non) Charger. With mine when cranking the engine, with the one field wire disconnected from the alternator there was no voltage on the wire when tested to earth with a voltmeter. On further inspection the field wire had about four bad connections between the alternator and the voltage regulator. Replaced the wire, got approx 10v to the alternaor from the field wire and all good 14.4v at battery when running. Hope this helps

Shayne

Be careful as the main feed to the alternator is permanently live

Just had a quick read of this.....sorry if Ive missed it but have you taken a reading from the main stud on the back of the alternator to earth while the car is running??

If its around 14V, I think your alternator will be ok and it will point to something else being a problem maybe?? If its at the 12.3V that you are getting at the VR then you will know that the VR is only working with what its being given by the alternator, pointing to it being an alternator problem. Try putting a good earth lead from the alternator mounting stud to earth on the frame. That can help and I do it as a matter of course on my cars.

If its 14V at the alternator and 12.3 at the ALT side of VR, maybe the wiring between both is suspect (easy to run new wires to test with spade connectors and bullet terminals). If its 14V one side of the VR and 12.3 the other side with everything on (lights etc), might be the VR? You would expect the higher reading with everything on as the system will recognise that it not only needs 12V or so to run everything, it also needs an amount over and above that to keep the battery topped up

Have you done the MAD electrical bulkhead connector bypass that we all tend to do? This cuts out the huge amount of electrical connections between the alternator and battery in the standard layout and simplifies the charging system? Well worth doing.

Just some food for thought....Im no expert but would recommend a methodic process of elimination working from the alternator to the battery ie the source of the power you are working with to the end product.

Good luck and please keep us posted. We are all sponges and Im sure that when you get this sorted we will all have learned from it!

Cheers Steve

Thanks Shayne and Steve, I'm getting same voltage from back of alternator as battery. Both started off at 12.8v and now dropped to 11.5v after a 4 hour round trip. So is it field windings not telling alternator to work or alternator not working? I've read about shorting out field wiring which bring alternator into full state but I'm not 100% on that and it sounds like i could cause more damage! Wondering if to take alternator off and get it tested.

Im guessing faulty alternator if the output is that low from the alternator. I think you will find one new for under £100 over here

rockinrich01 wrote:Thanks Shayne and Steve, I'm getting same voltage from back of alternator as battery. Both started off at 12.8v and now dropped to 11.5v after a 4 hour round trip. So is it field windings not telling alternator to work or alternator not working? I've read about shorting out field wiring which bring alternator into full state but I'm not 100% on that and it sounds like i could cause more damage! Wondering if to take alternator off and get it tested.

Rich,
I would test the field wire(s) for voltage, this is the exciter feed so if these are not working you will only read battery voltage at the back of the alternator. If these are good then take the alternator and get it bench tested

Shayne

if it just started doing it over winter that sounds more like poor connections or bad earthing.

start the car up with the fan belt off you'll be fine for 10 minutes

carefully (no chopped off hands please) see if the alternator is stiff to turn.

if its not you are not putting anything into the field.

you have two types of regulator and 2 types of alternator

all can be made to work together

but the old type regulator and some of the 2 field pin alternators need some jiggery pokery

a regulator with 2 pins for wires to the 2 field connectors controls the alternator by varying the voltage to both....the mismatch between the two dictates what voltage the field coils see

the other type expects one end of the field coil to be earthed (inside the alternator or via the connector on the outside) while it varies the voltage to the other end

if all parts are original style you don't need to worry

but if you had an alternator off a 73 and a regulator of a 68 you might.

if someone can get you the alternator section from the workshop manual

there is a full and easy to follow test routine that you can do with a meter
it tells you exactly which pins to put to 12 volts and which to earth out to prove your Alt is in good health.

I don't have a US manual and aussie Alternators are BOSCH and Lucas not Prestolite

Dave

Well looks like problem sorted, took alternator off and both my regulators and took them to Albaston starter's and rewinds on Monday. Picked them up today, alternator repaired (damaged brushes) and picked up new regulator, all for £45. One grey regulator wasn't reliable ( only 6 months old) and the other regulator was kickin out to much 15v+ ( only 3 months old).
Anyway, bolted back on with new regulator and running fine at 14.4v.
Happy days, off out to the strip tommorrow.

Glad you got it sorted, Rich.

Have fun!