5.7 Hemi Engine swap on 70 RR (Project)

[5.7 hemi]

https://www.backyardmechanic.org/how-to-build-a-external-voltage-regulator-for-dodge-jeep-chrysler/

Check it out.

 

[Caterpillars]

The factory computer controls the alternator output. You can bypass this setup by using the old school Mopar charging system. Give me a minute to find it.

I did bypass the computer by using and old style regulator set up - getting the same, even with no wire on the main alternator terminal.

 

[70chall440]

What do you mean "no wire on the main alternator terminal"? You mean the main lug where the charging wire goes?

 

[70chall440]

Ok, thinking this through, if you get an alternator and wire it in like an old school mopar, it should not produce 20V, so this tells me that it is something specific to your application. Are you spinning it too fast (not sure this would be produce what you are seeing). I do know that I had to change pulleys on one of mine because it wasn't charging enough (had to put a larger pulley on).

 

[Caterpillars]

Ok, thinking this through, if you get an alternator and wire it in like an old school mopar, it should not produce 20V, so this tells me that it is something specific to your application. Are you spinning it too fast (not sure this would be produce what you are seeing). I do know that I had to change pulleys on one of mine because it wasn't charging enough (had to put a larger pulley on).

The motor is operating on a serpentine system and is a factory crate motor.

 

[Caterpillars]

https://www.backyardmechanic.org/how-to-build-a-external-voltage-regulator-for-dodge-jeep-chrysler/

Check it out.

Thanks for sending link - definitely going to look at it closer.

 

[chtampa]

I had the same application and the Denso Alternator fried. I took the alt to a rebuild shop and they changed it inside and I have been using it for 2k miles so far. I took them a Mopar diagram of the 70 regulator and they made a change. Not sure what they did but he said he had a fix within a minute of looking at it.

 

[Caterpillars]

Order a new adjustable external voltage regulator and wire it in. The main wire was getting warm so I ran a new wire directly to the battery from the main terminal of the alternator. This resolved the heat but now things are fluttering - volt meter and brake light. I adjusted the voltage regulator to its lowest setting and I'm still getting almost 15 volts (better that 20);

Shut everything down and was planning on tightening everything - then the motor wouldn't start. I thought maybe I burned up the starter relay and changed it, nothing. I then changed all the relays on the new computer and it started. I added the wire to the main terminal that goes to the old amp-meter circuit but then thought that it may be a source of drain if I'm connected straight to the battery. I think I can live with this setup and need to clean up my mess (lab) and make it look pretty, but I wondering - I'm using a deep cell battery mainly because it has the convenient lugs on top to add circuits. Is it possible that this deep cell battery is causing some of my problems. I going to switch to a regular auto battery tomorrow (or when I get to it) to see if the voltage goes down a little. The car seems to run really good and can't wait to drive it.

 

[70chall440]

The deep cell should not have any affect to this situation IMO. How did you adjust the voltage regulator?

 

[Caterpillars]

There is a little screw on the back of the regulator. Suppose to set at 1.74. I screwed the screw all the way and now getting 14.7 Volts. This guy explains it;


Will leave the battery alone right now (based on your advise).. Going to run the main lug alternator wire to the starter wire coming from the battery - little cleaner look than running it across the engine and then to the battery. I'm still getting the pulsation on everything - maybe the voltage regulator is having fits? Got to get the answer to make it stop.

 

[70chall440]

Thats pretty interesting, never saw an adjustable before.

When you say you are going to run the wire from the alternator to the starter wire, are you connecting the alternator wire at the starter or at the starter relay?

What I do is this, I run a #6 cable from the alternator to a resettable breaker (size depends on the amperage out put of the alternator), then run a #6 cable from the breaker to the starter relay. This is of course where everything comes in and goes out (battery comes to it, starter wire goes out). You can get the breakers at any parts store, but it will save you in case your alternator goes stupid (which yours seems to be having issues with).

 

[Caterpillars]

I connected the main lug of alternator with #6 wire to the starter wire at the starter. The starter is connected to positive lug of battery. From the main lug of battery I connected #6 to starter relay. Also connected to starter relay is power to bulkhead going to old amp-meter (red wire, fused with 40amp). The other amp-meter wire (black, also fused with 40amp) is now connected to alternator (don't need to but did). The external regulator has one wire connect to ignition (blue) and to positive side of field on alternator. The other field wire on alternator is connected to green wire on external voltage regulator. Ran a direct ground from voltage regulator to alternator. Still pulsating - wonder what is the cause... My version of a homemade one wire alternator using external voltage regulator. Tried to make a video but it came out bad;



Time to take it for a little ride...

 

[70chall440]

I am going to go out on a limb here and say that your "direct ground from the VR to the alternator" is not doing you any favors. Ground it to something else like the engine (assuming it has a ground to the chassis) or to the chassis itself (ensuring it is a good clean ground).

I don't have an electrical degree but I have done a lot of electrical work (because I own a Mopar... LOL). I cannot say I have ever seen a pulsating alternator, so based on reading what you have wrote, it seems like you have eliminated most sources but you may be experiencing something like a coil effect where electrical current is passing into or through your grounds. You see this in electronic equipment where the cables must be shielded.

Your #6 cable to the start should work ok as essentially the same way I do it except I go to the starter relay but in the end you have the same connection there. In a grander sense these are relatively simple, the alternator turns and produces current, the VR regulates that. I suspect it is a simple deal, but not simple to find.

Have you read this thread?
https://www.forabodiesonly.com/mopar/threads/alternator-pulsing.229968/

 

[Caterpillars]

I am going to go out on a limb here and say that your "direct ground from the VR to the alternator" is not doing you any favors. Ground it to something else like the engine (assuming it has a ground to the chassis) or to the chassis itself (ensuring it is a good clean ground).

I don't have an electrical degree but I have done a lot of electrical work (because I own a Mopar... LOL). I cannot say I have ever seen a pulsating alternator, so based on reading what you have wrote, it seems like you have eliminated most sources but you may be experiencing something like a coil effect where electrical current is passing into or through your grounds. You see this in electronic equipment where the cables must be shielded.

Your #6 cable to the start should work ok as essentially the same way I do it except I go to the starter relay but in the end you have the same connection there. In a grander sense these are relatively simple, the alternator turns and produces current, the VR regulates that. I suspect it is a simple deal, but not simple to find.

Have you read this thread?
https://www.forabodiesonly.com/mopar/threads/alternator-pulsing.229968/

Thanks for all your help. Will check grounds tomorrow.

 

[70chall440]

No problem, I completely know what it is like to chase a problem, do it all the time..

 

[Caterpillars]

This car has demons. After getting ready to go for a ride my engine won't start. All the problems I was having points to the (POS) pcm that mopar supplied with the crate engine kit. The alternator over charging - the pcm controls the voltage. The pulsating lights - maybe the pcm? Now no 12v to coils or fuel injectors. Could be a cam or crank positioning sensor, but the alternator overcharging. Of course mopar gave me a no access non programmable pcm, so I can't look for codes or run diagnostics. You just have to get a new one, and guess what - they don't make them anymore and there support sucks. So I went and signed up on a late model Challenger site thinking there has got to be a bunch of computer experts - not much help. So maybe someone on here knows what I can do. If I have to get a new PCM I would prefer one that I can access and pull codes from, and maybe tune a little. Anyone?

 

[5.7 hemi]

Call Chris @ hotwireauto.com he can help you get squared away.

 

[Caterpillars]

Call Chris @ hotwireauto.com he can help you get squared away.

Thanks for the suggestion. Talked to Chris, nice guy, but he thinks I should change my computer, wiring harness, gas pedal, and of course would need to get a new intake and throttle body. This sounds like some $$$. I get it, he is trying to make a living, but everything on this car is already new. I just have a problem I need to solve. Wish I had a good wiring diagram...

 

[5.7 hemi]

Gotcha.

Bouchilon might be able to answer your questions.

 

[CudaFish]

This car has demons. After getting ready to go for a ride my engine won't start. All the problems I was having points to the (POS) pcm that mopar supplied with the crate engine kit. The alternator over charging - the pcm controls the voltage. The pulsating lights - maybe the pcm? Now no 12v to coils or fuel injectors. Could be a cam or crank positioning sensor, but the alternator overcharging. Of course mopar gave me a no access non programmable pcm, so I can't look for codes or run diagnostics. You just have to get a new one, and guess what - they don't make them anymore and there support sucks. So I went and signed up on a late model Challenger site thinking there has got to be a bunch of computer experts - not much help. So maybe someone on here knows what I can do. If I have to get a new PCM I would prefer one that I can access and pull codes from, and maybe tune a little. Anyone?

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I know this is the B body forum. Had same problem and this was my fix.
I have completed a 2004 5.7 Hemi swap in my 68 Barracuda, I tried to use the flat 2 wire mopar voltage regulator with the bosch alternator. It charged at like 20 vdc. I took the alternator to a guy and he removed the pwm voltage regulator and installed a "non pwm voltage" regulator on the alternator and it has has a small 12vdc light bulb to excite the alternator to charge. It puts out a constant 14.5 vdc. He was hoping he could excite the alternator internally, but could not with what he had. A competent alternator shop should know how to do this. I hope this will help some people out. Just my $.02 experience.