HELP! Newb! Radio dies when put in reverse/signal/brake. Signals seem slow and delayed as of recent
- Thread starter Salvatore
- Start date
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let's start here:
7509 is the 'Lester' number which is widely used in the aftermarket interchange business. DP is dual pulley
The pulley looks like it might be a Chrysler original, which means it can actually be removed with puller and will line up correctly when installed.
However, we only see one sheave being used.
Does the crank have a dual pulley or a single pulley? Is there power steering?
Bottom line is that its OK if there is an unused sheave as long the belt lines up and the pulley ratio is correct.
It looks like a 7509 is usually called a '60 amp'
7509 is the 'Lester' number which is widely used in the aftermarket interchange business. DP is dual pulley
The pulley looks like it might be a Chrysler original, which means it can actually be removed with puller and will line up correctly when installed.
However, we only see one sheave being used.
Does the crank have a dual pulley or a single pulley? Is there power steering?
Bottom line is that its OK if there is an unused sheave as long the belt lines up and the pulley ratio is correct.
It looks like a 7509 is usually called a '60 amp'
Correct choice is somewhat dependent on what you want.
If the only electrical change from stock is the aftermarket radio/tape/cd deck, and its low power, then there's no need for higher 'rated' alternators than factory. The ratings are somewhat arbitrary.
A higher output alternator can be a double edged sword. If it can produce more power at idle speeds, then the battery won't be drawn upon when running lots of electric equipment (lights, wipers, fanm, brake lights). Then there's no need for the alternator to recharge the battery except after starting. This is a good thing.
But, lets say the battery is run low - and a deep cycle is made for that. A higher output at idle means it can and will provide a high charging rate for a very low battery. This is bad for the battery and bad for the wiring - both of which will got hot with high current flowing though them. Granted if we drive on the highway, even the local highways, with a standard output alternator the same problem can arise. But at least we have the option to slow down or pull off and let it idle. (Use the ammeter to monitor the charging rate. )
The most likely places the deck is wired into - battery positive terminal or starter relay - or the fuse box - or a wire off of the fusebox.
or maybe used the original radio power wire.
Blue is power supply to the rotor. It is also the 'sense' wire for the voltage regulator.
Green is the ground side of the rotor. It goes to the voltage regulator, which controls whether the connection to ground is open, closed (maximum flow) or connected to ground through resistors (restricted flow). With current flowing through the rotor windings, the rotor becomes a spinning electromagnetic field. The strength of the field is controlled by rapidly switching the connection inside the regulator.
This is a '67 so the wiring will look a little different than your '73.
But I happen to have the same style alternator on it as your car should have.
Wire on the output stud of a '73 may have a protective boot covering it. The case next to the stud may be marked BATT
Ok. Then maybe you'll find graphics helpful.
'73 Power circuits look something like this. The circle in J2 represents a junction (splice?) to the choke assist if there was one on the original engine.
(Accessory wire from the key switch goes to the wipers and to the 'switched' portion of the fuse box. Radio fuse was only on when key was in Run or Accessory positions)
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A quick check of the major connections.
With the key off, all of the wires connected to the battery positive should be a the same voltage.
Arrow points to some of the connections. Brake and Dome and parking light feeds are also hot.
Or you can disconnect the battery and check for continuity.
With Key in Run J2C, J2A, J2 should all be at system voltage.
Engine running, feed to the rotor should be close to system voltage.
A quick check of the VR would be to jumper the field terminal to ground.
This will allow full current through the rotor, aka 'full fielding'
Output voltage when running should be around 14 V and increase with rpm.
The ammeter should show charging after start, if only briefly.
if voltage is increasing with rpm, do not rev the engine because voltages much above 15 V will cause everything to draw more current than is healthy. Can burn out light bulbs and everything else too.
With the key off, all of the wires connected to the battery positive should be a the same voltage.
Arrow points to some of the connections. Brake and Dome and parking light feeds are also hot.
Or you can disconnect the battery and check for continuity.
With Key in Run J2C, J2A, J2 should all be at system voltage.
Engine running, feed to the rotor should be close to system voltage.
A quick check of the VR would be to jumper the field terminal to ground.
This will allow full current through the rotor, aka 'full fielding'
Output voltage when running should be around 14 V and increase with rpm.
The ammeter should show charging after start, if only briefly.
if voltage is increasing with rpm, do not rev the engine because voltages much above 15 V will cause everything to draw more current than is healthy. Can burn out light bulbs and everything else too.
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Bench testing most parts of a square back alternator is relatively easy.
Replacing any of the parts is also easy.
Only changing the rotor requires a puller and a press.
Alternator repair, a little show and tell.
Replacing any of the parts is also easy.
Only changing the rotor requires a puller and a press.
Alternator repair, a little show and tell.
Yes I do have power steering. I have only one belt tho and one on the crank. You think I could Get away with the single groove unit ? They are 60 amp 2 groove or 65 amp Single groove. My battery output is at 55amp I believe the yellow top optima has. I figured go with what’s there but what if it’s wrong. I can get one for $99 new or refurbished from my local parts store. Can I just pull the whole alternator and replace it using hand tools, visually looms doable . Seems like a quick and easy solution considering the current diagnostic point in at. I’m yet to start getting into taking all the multiple readings as I took it out original last night too start my readings and then got stuck after being tempted to go for a short cruise . I have looked over your schematics and drawings and they have been very helpful understanding the mapping
I would first make sure the problem is the alternator.
Put the battery on a smart charger, or lowest setting.
Then check the connections to the rotor
Then check to if bypassing the VR changes things.
In any event, the ACTUAL current output will be whatever the demand is. The ignition running at idle is going to take about 3 amps. If nothing else needs power, then thats all the alternator will put out, 3 amps around 14 Volts, or 42 Watts of power. (V x I = Power)
The battery has several ratings. One will be Cold Crankings Amps, another will be Amp - Hours. Again it will provide only as much current as there is demand. However, after its been used, it will suck power until recharged. This is where it gets tricky. Most devices draw X amount of current when supplied at a given voltage. Increase the voltage and they will draw more. We can see that with the headlights. On battery (12ish Volts) the lights look dimmer than when the alternator is working (14ish Volts). Give them 18 Volts and they'll draw even more (and burn out).
Battery draw depend on voltage and its state of charge. A heavily discharged battery will draw 30 or 40 amps at 14 Volts, assuming that much power can be supplied. A fully recharged battery will draw essentially no current at 14 volts.
Put the battery on a smart charger, or lowest setting.
Then check the connections to the rotor
When the battery is fully charged, start the car and see what the voltage is at the battery positive, the alternator output, and the rotor feed (blue field terminal - probe through the back of the connector)
Then check to if bypassing the VR changes things.
Maybe. Someone may know off the top of their head. I'd need to check the parts book to be more confident.
Thems alternator ratings are not quite meaningless but we have no idea how the remanucturers come up with these numbers. It's probably something close to maximum output, but even there, they can play games by testing at lower voltages. We don't even really know how Chrysler determined their alternator ratings. In 1973, what Chrysler called 65 amp unit was a special alternator made by Leece Neville that had a slightly differnet wiring and regulator.
In any event, the ACTUAL current output will be whatever the demand is. The ignition running at idle is going to take about 3 amps. If nothing else needs power, then thats all the alternator will put out, 3 amps around 14 Volts, or 42 Watts of power. (V x I = Power)
The battery has several ratings. One will be Cold Crankings Amps, another will be Amp - Hours. Again it will provide only as much current as there is demand. However, after its been used, it will suck power until recharged. This is where it gets tricky. Most devices draw X amount of current when supplied at a given voltage. Increase the voltage and they will draw more. We can see that with the headlights. On battery (12ish Volts) the lights look dimmer than when the alternator is working (14ish Volts). Give them 18 Volts and they'll draw even more (and burn out).
Battery draw depend on voltage and its state of charge. A heavily discharged battery will draw 30 or 40 amps at 14 Volts, assuming that much power can be supplied. A fully recharged battery will draw essentially no current at 14 volts.
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Get a '73 Shop manual. Bishko sells them reprint or CD. Used ones come up for sale.
In the meantime if you have the bandwidth, go to Mymopar.com and download a '73 Dodge from the ref section for free.
I downloaded that one because I needed the '73 up alternator repair info.
For '73 some of the current ratings are the same as the test specifications at 1250 engine rpm.
However this is unusual. Most of the time alternator ratings are higher than the test specs at 1250.
Also notice that if the current is measured at the battery, it will be 5 amps less.
Those 5 amps get diverted to the ignition and rotor.
Finally, notice the test voltage is 15. This makes it a tougher test than if it had been run at 14 or 13.2 Volts.
We can look at a late squareback that the remanufacturer called '78 Amps' unit, and pencil in the difference in maximum outputs at different voltages.
The maximum power generated available remains the same. P =IV. Lowing Voltage increases amperage available.
Lets just say for the sake of an example that the 15 Volt line is correct.
And lets say the alternator is driven at 2.5 times the crank speed.
So using '73 Chrysler test, at 3125 alternator rpm, this unit was maxing out around 55 amps. H'm. How 'bout that.
In the meantime if you have the bandwidth, go to Mymopar.com and download a '73 Dodge from the ref section for free.
I downloaded that one because I needed the '73 up alternator repair info.
For '73 some of the current ratings are the same as the test specifications at 1250 engine rpm.
However this is unusual. Most of the time alternator ratings are higher than the test specs at 1250.
Also notice that if the current is measured at the battery, it will be 5 amps less.
Those 5 amps get diverted to the ignition and rotor.
Finally, notice the test voltage is 15. This makes it a tougher test than if it had been run at 14 or 13.2 Volts.
We can look at a late squareback that the remanufacturer called '78 Amps' unit, and pencil in the difference in maximum outputs at different voltages.
The maximum power generated available remains the same. P =IV. Lowing Voltage increases amperage available.
Lets just say for the sake of an example that the 15 Volt line is correct.
And lets say the alternator is driven at 2.5 times the crank speed.
So using '73 Chrysler test, at 3125 alternator rpm, this unit was maxing out around 55 amps. H'm. How 'bout that.
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One of the other Matts here wrote to think of current like a stream. The stream, whether it comes from the alt or the battery, then flows into the different branches.
I made an animated gif of a pre '70 system showing the flow after starting.
(not shown is flow through the grounds)
I made an animated gif of a pre '70 system showing the flow after starting.
(not shown is flow through the grounds)
If the problem turns out to be the alternator,
Then we can walk through some basic bench checks.
if its the regulator, just get a new one.
If its the wiring is choking the flow, we'll have to track down where, but the bulkhead and steering column connectors are often problem spots.
Then we can walk through some basic bench checks.
if its the regulator, just get a new one.
If its the wiring is choking the flow, we'll have to track down where, but the bulkhead and steering column connectors are often problem spots.
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I will go through theses checks as I do have a good quality agm specific charger hooked up currently.
Just to add I can tell my brake lights and signals and deck are solely surviving off of my battery. As soon as my batter dies my signals barely come on if not won’t, and the car can choke and die and not enough charge to restart. Just to be confident do I need a specific tool of the trade to get my belt tight or is simply prying up By hand and setting the bolt on the tensioner Slotting by wrench good enough ?
On these I just pull it will my hand until it feels like some tension. Then after tightning the bolts, check for a 1/4 - 1/2' deflection on the long stretch of belt, without too much force. There's a deflection for x pounds in the shop manual. If you have fish scale you could use that with a ruler to see if its about right.
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