Another Charging Question

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dennday67

dennday67

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So the car is a 68 Valiant /6. When I got it every thing was stock and wiring harness was in good shape and not hacked up. All connection changes I've made as crimp, soldered, and shrink tubed. I've since done the HEI upgrade so all wires going to the ballast have been soldered together and are going to the upgraded dual field VR and 78A (I think might be lower) Alt. I bypassed the AMP gauge by running a 10ga wire straight from the Alt to the starter relay (currently unprotected) and completely removed the original red power wire from the bulk head connector. Ive upgraded the headlights using two SPST relays mounted in a sealed box under the battery, ceramic headlight sockets and 12ga wire pulling from the starter relay (that removed light flicker and idle). I tested my IGN switch and seemed like I was loosing over .5V through the switch so I changed it. Ive been working on swapping the dash, parking lights, and tail lights over to LED to reduce the amount of draw on the system. My problem is at idle lights off I'm only charging at 13v and off idle 14.2v. With lights on at a stop light it drops all the way down to 11.7v. I've double checked all grounds and added a few more (one going from the VR to the alt body). Can I change the ALT to something better or change the pulley so it spins faster or should I be looking further into the wiring harness. One test I checked was key on (motor off) ground to the blue/white wire at the bulk head connector was showing almost .7v different than static battery but not sure from what.
 
First thing you need to do is determine if it's the alternator, and whether it's something WRONG with the alternator (like a blown diode) or whether it's something else.

Do some tests.

Bypass the VR, but monitor battery so it does not go much over voltage. Try to keep it below 16. To do that warm it up, get some clip leads and your meter, and try to duplicate the low voltage / lights on condition.

To bypass the VR, remove the green field wire (goes to the VR) and ground that alternator terminal with a clip lead. Now duplicate your headlights condition, and see what you have for idle and off idle voltage.

If it is still low, compare battery and alternator output terminal voltage to make sure they are close to the same. Again, idle and off idle

If charging is still low, do whatever is cheapest. Either have the alternator checked or try a different on. The squarebacks are much better for low/ med charge voltage
 
The ALT is a square back unit. So I ran a couple test under different conditions and here is what I got all warm.

Battery ALT
Running idle with lights off
13.6 13.9
Running off idle with lights off
13.8 14.2
Running idle with lights on
12.9 13.3
Running idle lights on in gear with foot on brake
12.2 12.5
Running idle and off idle ALT FLD grounded (top post of alt) with lights on and off.
12 12
So the ALT is bad?
 
Does it matter which way the field wires are hooked up coming from the VR? I seem to recall someone telling me they don't but want to be sure.
 
There is no way to know if the alternator is bad from what you posted there. ALL alternators will "drop off" "at some point"

Are those voltages with the VR bypassed, in other words "full field" voltage to the field?

No, field hookup does not matter. You can reverse the wires.

Some possibilities...........

Alternator might not be "the one" you think it is. There is a difference in output with different alternators. As old as these girls are, and with the "mixup" in parts from rebuilders, that might be difficult to determine.

Alternator might just plain be turning over too slow. There is NO GUARANTEE that these girls every "put out" 14V at a dead idle, orginally!!!

Alternator might have a problem. Only "ways" to know that is to read the shop manual and perform a full load test, take it to a parts store with a "good tester" (which may or may not be) or to a rebuilder (local) who really knows what he is doing.

Here's a better question......."Does it really matter" that the voltage sags at a dead idle?
 
I got 12v with the green field wire disconnected and that post of the alt grounded to the case with a jumper (other field wire still hooked up). No matter what I did be it on/off lights, brakes, in gear, or off idle it remained at 12v. In the voltage difference between the alt and battery acceptable? I've seen the voltage drop as low as 11.5 in gear with the lights on so I upped the idle to get it up a bit higher. That just seemed too low to me for the HEI. If I swap the alt what would be a good upgrade (square back or denso) and with my setup what's the safe Max amp alt?
 
You lost me when you removed the original red power wire from bulkhead connector. What happens when you put it back?
 
When I pull the cluster gauges ill double check the wiring going to the amp gauge but the bulkhead connector looked a little melted and the owner of smiths auto electric said once I ran an up sized wire from the alt to the battery I could just remove the original power wire so I did.
 
I pulled the cluster and the amp gauge is still hooked up correctly just not using it anymore.
 
Decided to go with a 90 amp 88-89 denso alt. Alternator is order, got some 6ga wire to replace the 10ga I was running, and still need to order a fuse or automotive breaker (not a big fan of fuseable links). Also not sure if I should reinstall the orginal red wire back to the bulk head and hook the factor black wire to the starter relay or leave it hooked to the alt. I've red through many post and seems like everyone has different views.
 
Originally, the big red and big black wires not only feed alternator to the battery through the ammeter, they ALSO feed power into the interior. Read the Mad article. The simplified diagram in that article gives a very good idea of primary power.

ALL interior power comes off a great big welded factory splice in the BLACK ammeter wire, a few inches from the ammeter, up under the dash. Depending on the year, these branch off to feed.......

the headlights only power to the HL switch

the main power to the ignition switch

the "hot" feed to the hot buss in the fuse panel

So you need to "replace" this circuit path somehow The reason the MAD article does this "as they do" is that the "improved" connections of the RED and BLACK form one big parallel wire, meaning, an effective larger gauge wire into the interior, but with no power going through that path to the alternator, so "all" the wire size is now available to feed lower resistance into the interior

MadElectrical.com - Electrical Tech

Catalog

amp-ga18.jpg
 
Basically from the diagam take away the red wire from the bulk head to the relay and add from the alt to the battery is how its been for the last few years but I think I'm going to completely bypass the bulk head on both red and black and back to the alt gauge like mad recommends using some 8ga wire I have. What's your thoughts on breaker vs fuse?
 
Don't like the mad approach...

Run your direct charge line to the starter relay and leave all the factory wiring alone if it's in good condition.

I've been assembling charge lines and relay systems for our old car for a few years. Not a fan of pulling power off the starter relay and chopping up the factory harness. There are fusible links already in the system, except you aren't taxing them with a direct charge wire.
 
crackedback said:
Don't like the mad approach...

Run your direct charge line to the starter relay and leave all the factory wiring alone if it's in good condition.

I've been assembling charge lines and relay systems for our old car for a few years. Not a fan of pulling power off the starter relay and chopping up the factory harness. There are fusible links already in the system, except you aren't taxing them with a direct charge wire.
Click to expand...

Your opinion is duly noted but about 10 mins too late. My harness was in great shape but as I stated all fuseable links have been removed (they well be getting replaced) I've already bypassed the amp gauge, 6awg wire already ran and working on the interior ATM.
 
OH, I should have mentioned I bypass the POS ammeter... :)

Otherwise everything remains the same except with the direct charge line.
 
Swap is all done. At idle I now get 14.3v and in gear with the lights on stereo up I get 13v-13.3v. Throttle is more snappy, feels like its got more power, and stereo hits harder. Best $140 upgrade I've done. All that's left is to reinstall my F6 loom.
 
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