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Discussion Starter #1
So it seems like I am loosing voltage as the car gets up to temp. I am having a few issues with voltage loss and I am wondering if any of you have dealt with something like this? I just replaces my alternator with a new 150 amp 1 wire because I thought my old 110 amp was failing when it got hot. When the car gets hot the idle gets iratic and you can see the voltage gauge drop in the car on the gauge. However the alternator is still putting out 14 plus volts. I removed the original voltage regulator some years back. The Distributor is a new DUI unit. Most everything else is stock stuff. So I am scratching my head wondering what could be causing this voltage drop as the car gets hot? I am gona start chasing wires around tomarrow and do a bunch of checks for voltage as the wires travel threw the harness tomorrow. Just hopping maybe someone has dealt with something similar and can point me in a direction? Thanks guys.
 

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so what have you measured, in volts, that is low when hot... what wire are you losing voltage on?
 

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Discussion Starter #3
Back of the alternator measured 14.5 volts while the gauge in the car was reading 11.5 volts. I have not done step by step checks yet. I have to rip apart my entire harness to do that. What I know for sure is that when the car warms up the idle goes to crap. Its perfectly smooth before it gets hot. It will be running smooth at 900 rpms but once it's gets hot it drops and bounces all around. Also the gauge in the car reads much higher voltage before the car gets warm. I have bin dealing with this for a few weeks trying other things
 

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Al - Waterloo, Iowa
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Your possible voltage drop may not have anything to do with the idle problem. If by warming up you mean the few minutes it takes for the choke to come off I'd think the idle problem is not related to the voltage problem. On the voltage problem I would probe the in car gauge wires to see if you're truly dropping voltage and not just the gauge going/gone bad to start with.
 

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I would maybe start with looking at the main power feed wire in the bulkhead connector and see what the voltage is on the engine side vs the interior side.

Since you could have voltage drops when measuring these two spots, keep your meters ground to one spot. If on the engine side you were to ground your meter to the battery post but then when checking the voltage inside the car and you then place the meter ground to a metal spot under the dash you will get two different voltage readings but you will not know if the voltage drop is just on the positive side, just on the negative side, or a little drop on both sides.

Also keep in mind if you use one meter to measure something under the hood at the alternator and then have another gauge measuring things inside the difference seen might not be from a voltage difference but of the meters and gauges accuracy. Two meters with one reading 11.5V and another reading 14.5V is a lot but who knows sometimes.

Jim
 

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Check the connections at the horn relay including the fusible link. Then inspect the junction block located on the core support. Also make sure the battery cables are not corroded at the battery or the engine block. That should get the gauge reading correctly again unless the gauge itself is going bad.
 

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Discussion Starter #7
Your possible voltage drop may not have anything to do with the idle problem. If by warming up you mean the few minutes it takes for the choke to come off I'd think the idle problem is not related to the voltage problem. On the voltage problem I would probe the in car gauge wires to see if you're truly dropping voltage and not just the gauge going/gone bad to start with.
There is no choke so thats not a factor. The gauge is New but that dose not mean anything. I plan to do more extensive checks at several spots including the gauge tomorrow. Also have an older gauge I may try to see if it reads the same.
 

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Discussion Starter #8
I would maybe start with looking at the main power feed wire in the bulkhead connector and see what the voltage is on the engine side vs the interior side.

Since you could have voltage drops when measuring these two spots, keep your meters ground to one spot. If on the engine side you were to ground your meter to the battery post but then when checking the voltage inside the car and you then place the meter ground to a metal spot under the dash you will get two different voltage readings but you will not know if the voltage drop is just on the positive side, just on the negative side, or a little drop on both sides.

Also keep in mind if you use one meter to measure something under the hood at the alternator and then have another gauge measuring things inside the difference seen might not be from a voltage difference but of the meters and gauges accuracy. Two meters with one reading 11.5V and another reading 14.5V is a lot but who knows sometimes.

Jim
Thanks Jim, good point about the ground. I will do extensive testing tomorrow. Was really wondering hoping there was a known culprit for something like this =)
 

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Discussion Starter #9
Check the connections at the horn relay including the fusible link. Then inspect the junction block located on the core support. Also make sure the battery cables are not corroded at the battery or the engine block. That should get the gauge reading correctly again unless the gauge itself is going bad.
The battery and cables are new and clean. No corrosion. Thanks for the advice
 

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Thanks Jim, good point about the ground. I will do extensive testing tomorrow. Was really wondering hoping there was a known culprit for something like this =)
You just have to look at the amount of connections between your test points. You have a stud on the back of the alternator that then a ring terminal attaches to which is then crimped onto a wire which then this wire goes to let's say the horn buss which then at the end of this wire is a crimped on connector. The the connector bolts onto the horn buss then yet another connector is bolted to the horn buss with a crimped on wire end that then goes into a fusible link and then the wire goes to a crimped on connector at the engine side of the bulkhead connector. This connector then pushes into a mating connector which then is crimped onto a wire which then in the loom probably get's split with one leg going to the ignition switch and then another leg to the fuse block. At the wire end of the battery wire at the ignition switch, guess what, another crimped on terminal end that then pushes onto a terminal and goes inside the ignition switch.
These connections go on and on until it gets to your inside gauge. THEN it all has to get back to the source of power on the ground side.

NOW, if anyone has a crystal ball and can say exactly what connector or connection is the culprit, then they are the man.

Yep, you are just going to have to dig into things. There will be some voltage drops and this is normal but if the drop is excessive, then something is wrong.

Jim
 

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Discussion Starter #11
Well as a fallow up - I kinda cheezed the fix =). I got to the inside of the firewall with not crazy voltage drops. But once it went threw the ignition and under dash wiring the voltage dropped 1-1.5 volts at the distributor. I called the Manufacturer of the distributor and they confirmed the EFI style Distributors are VERY sensitive to voltage drops and that having the voltage drop that much would screw up the distributor. SO I wired up a relay that now feeds power from the main line to the distributor once ignition is turned on. I used the old feed line to the distributor to trigger the relay. Tomorrow I will clean up the wires and loom everything again. Before I lock it all down I wana drive the car and see what happens. I guess there is a resister or some resistor wire under the dash possibly but I did not feel like digging threw all that. The few things I have in the car work fine as is. SO untill I decide to Re-Wire the Entire car this is what I decided to do! Thanks for the Input guys =)
 

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OP

were you using the stock IGN (white wire) to the + coil for your HEI dizzy?

That is a resistance wire for points dizzy and would have needed to be replaced (bypassed) with a new wire from IGN tab on under dash fuse block
 

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Upgrade your main feed wire to either a 4 or 6 AWG. Are you still using the factory engine harness for the alternator connections?
 

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I wired up a relay that now feeds power from the main line to the distributor once ignition is turned on. I used the old feed line to the distributor to trigger the relay. Thanks for the Input guys =)
Hopefully wherever you got main power for your relay you added in either a properly sized fuse, breaker, or fusible link.

Jim
 

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Discussion Starter #15
OP

were you using the stock IGN (white wire) to the + coil for your HEI dizzy?

That is a resistance wire for points dizzy and would have needed to be replaced (bypassed) with a new wire from IGN tab on under dash fuse block
I am not sure what color the wire was but I am thinking it was probably the original one. I did not know that needed to be replaced but its a mute point now.

CHRIS - No not using the factory connections for the Alternator.

Jim - Yes I added a Fuse.

Thanks for the Input guys.
Cory C.
 

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I am not sure what color the wire was but I am thinking it was probably the original one. I did not know that needed to be replaced but its a mute point now.
Cory C.
...well it is a "point" regarding how well your HEI ignition will work. The stock wire would be white and covered with more like a cloth/rough insulation vs the normal smooth rubber regular wire is. That stock white wire knocks VDC down to around 8 vdc IIRC to the + coil terminal. Your HEI needs 12VDC

Regardless of what other issue is causing your interior volt meter to read low...you want to replace the resistance wire with a 10 gauge regular wire from at least the bulkhead forward if cutting the white wire...or, and more recommended way, is to just tape that white wire back into your wire loom and run a new 10 gauge wire from IGN terminal of under dash fuse block to your + coil terminal if using a HEI dizzy.
 

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Discussion Starter #17
...well it is a "point" regarding how well your HEI ignition will work. The stock wire would be white and covered with more like a cloth/rough insulation vs the normal smooth rubber regular wire is. That stock white wire knocks VDC down to around 8 vdc IIRC to the + coil terminal. Your HEI needs 12VDC

Regardless of what other issue is causing your interior volt meter to read low...you want to replace the resistance wire with a 10 gauge regular wire from at least the bulkhead forward if cutting the white wire...or, and more recommended way, is to just tape that white wire back into your wire loom and run a new 10 gauge wire from IGN terminal of under dash fuse block to your + coil terminal if using a HEI dizzy.
I understand and I can only assume that wire was replace removed before I got the car. Lowest voltage I ever read before I installed the relay was 11.5 which is a LOT more than 8V. Also the wire is a pinkish color and NOT cloth so someone got to it before I did I guess =).

I am STILL having Issues with this system. The problem is when the electric fans Kick on the Voltage across the entire system Drops. When the Car first starts it reading about 14V across the power lines Under the hood. Once the Fans kick on the voltage it dropping like 1.2 or More volts. This drop in voltage is causing the distributor to change its output and the Idle drops as well! It goes from 900RPMs to like 700RPMs. I have called Performance distributors like 6 times today and they are working with me to try and figure this out. Tested many grounds and various other things but have not found a resolution yet. When the car is running @ 2000 RPMs the problem is not as bad but still happens, the fans come on it looses about 50 RPMs and about 0.7 Volts. The Alternator (a 150V Powermaster) is tested good and doing what it Should. I am at a Loss and honestly so are they. Dose anyone have any Insight as to what could be causing this? Is it normal to see that Kinda drop in voltage when electric fans come on? Dosent seem like it should do that? I an struggling to figure this out. ANY Ideas are Welcome - PLEASE =)
 

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I'm going to bet some of the issues to be is that your "150A Powermaster" at the RPM it is spinning is not keeping up with demands. Any alternator has an output curve like below and if the demands are larger than the supply from the alternator the voltage will go down.

From Powermaster:

Power Pulleys

Here is an output curve sheet on a particular case alternator and having different output amperages.



In the above, the 63A alternator at about 1500 RPM is outputting 25A while the larger output 72A is not even outputting anything yet at that RPM. The 72A has to be spun at about 2000RPM for it to put out 25A.

Another concern is maybe you need to do the "Big Three" upgrade and this basically started in the car audio sector and it has a larger power wire from the alternator output directly to the battery as well as a large ground from the alternator case to the battery and then if things are grounded to the car body, a large ground wire is run between the battery negative post or the alternator case to the body of the car and all added electrical items are source from the battery positive post.

If by raising the engine rpm to something like 2500 RPM and now the voltage does not drop, then this again leads me to an alternator output issue.

Jim
 

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Discussion Starter #20
Check the amperage draw on the fans when they engage. Then compare that with the fans labels. They may just flat be bad or designed for a different system.
Ya, I was thinking in that relm myself. They are Spal fans and supposedly the pull 18Amps each. They are intended to be universal but who knows. I went and grabbed some 4th gen fans out of the salvage yard today. I was gona try to put them in place of the others and see if they did the same thing or not? Just curious if I eliminated those fans altogether what would happen. Thanks for the idea man
 
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