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-   -   stumped on alternator issue (https://www.viperalley.com/forum/showthread.php?t=296283)

daaam September 17th, 2019 12:07 PM

stumped on alternator issue
 
So I posted a while back about my 96 R/T 10 (RSI twin Turbo) not charging properly as when I first start the car it charges fine at 14.3 volts and stays consistent. Then if it runs for 5 minutes or more and I shut the car off and start it up within an hour or so the voltage will only start around 14 volts or less and they will keep dropping off down below 13.5 volts. I wired an external voltage regulator to the alternator and it is doing the exact same thing. The voltage gets so low that I will eventually not be able to start my car.

I have gone through 3 alternators and a starter trying to figure this out and nothing changes. So yesterday just for the hell of it I wire another ground wire directly to the alternator (14 gauge) (I already have one on it from the external voltage regulator) and the alternator acts the same way but I gain .1volts. I put another 14 gauge ground on just to see what happens and I gain another .1 volts. I am so confused on what is going on. So with the 2 extra ground wires I see across the boards a .2 voltage increase. So with load on the alternator (lights on, a/c on high, radio on, etc... it was dropping down to around 13.2 volts but with the extra ground wires I was getting it back up to around 13.4, 13.5. Just to be sure I bought a second external voltage regulator and it acts the same way.

Does anyone have any idea what is going on? I am so confused how when I start the car cold it works fine for as long as I drive it, then once I shut it off and start it again then it starts acting up. I thought maybe a ground issue but how can it be perfectly fine at first then on re-start it isn't? Any help would be greatly appreciated.

99RT10&GTS September 17th, 2019 05:01 PM

Check the ground strap near the front right side of the engine. If it is loose or disconnected, it could be causing the problem. I have heard it can cause problems with the oil cooler lines too.

daaam September 17th, 2019 05:59 PM

Quote:

Originally Posted by 99RT10>S (Post 4679397)
Check the ground strap near the front right side of the engine. If it is loose or disconnected, it could be causing the problem. I have heard it can cause problems with the oil cooler lines too.

I am thinking this is probably the issue as I just touched a 4 gauge wire on the alternator and touched the other end to ground and it went from 13.5 up to over 14 volts.

I looked and couldn't see this ground strap from the engine. Just to clarify is it drivers or passengers side? Also do you have any better description on where on the engine it's connected too? Can I get to it or see it from the top of engine or do i have to get under the car? Remember this is a gen 1 engine.

Thanks!

jslimm September 17th, 2019 10:27 PM

Quote:

Originally Posted by 99RT10>S (Post 4679397)
Check the ground strap near the front right side of the engine. If it is loose or disconnected, it could be causing the problem. I have heard it can cause problems with the oil cooler lines too.

I like that possible cause !

This makes me think that I very dimly remember a thread about some problem that led to discovering that the engine block was connected to ground only (or primarily) through the braided oil lines and connections.

99RT10&GTS September 18th, 2019 03:30 PM

It should be on the passenger side bolted to the frame.

CWhiteRun November 2nd, 2019 08:18 PM

Remove the pin from the ECU connector that is responsible for field control. Also, measure resistance from the back of the alternator to the post on the front of the under hood fuse block and post it here.

Lunchbox November 4th, 2019 12:29 PM

Have you checked the battery temp sensor? If you've gone through alternators, starters and ground wires, this might be something to check in addition.

daaam November 4th, 2019 01:04 PM

Quote:

Originally Posted by Lunchbox (Post 4683975)
Have you checked the battery temp sensor? If you've gone through alternators, starters and ground wires, this might be something to check in addition.

The 96RT-10's don't have the battery temp sensor. Thanks for the thought.

daaam November 4th, 2019 01:07 PM

Quote:

Originally Posted by CWhiteRun (Post 4683897)
Remove the pin from the ECU connector that is responsible for field control. Also, measure resistance from the back of the alternator to the post on the front of the under hood fuse block and post it here.

I don't know how to measure the resistance. I did run a power wire from the fusebox and hooked it up to the sense wire on the alternator and at idle (when hot) the alternator is at under 13 volts (just like with factory wire hooked up) but with any rpm given (even 100rpm) then it jumps back up to 14.3 volts at the alternator post. I have a .2 volt drop from the alternator post to my battery which I think is acceptable (that .2 volts drop has been consistent with all my tests I have done). I am thinking that somehow the sense wire may be bad.

I literally bought zero gauge wire and ran it right from the alternator to the battery and the same issue occurs when alternator is hot. The only thing that has changed anything is me changing to the sense wire to a 12 volt source from the fuse box. I still feel like the alternator never got so low at idle in the past when i had no issues, but owners manual says to test alternator at 1500 rpm and then I do that it is charging at 14.3 volts. It is just weird that at idle when the car is cold that it charges at 14.55 volts but as it heat soaks it goes so low.

I am just going to replace the sense wire for now and try it next spring to see if this solves my issue. If not I will be back but I am not sure what else I can do as I tried zero gauge right from alternator to battery, zero gauge from alternator to power post under hood then right to battery. I replace grounds on vehicle and to battery with zero gauge wire. I tried hooking zero gauge wire directly from battery negative terminal to the alternator, and everything I do I get the same results except for the sense wire. I did almost every combination of connecting wires that I could think of and even at the alternator the charging level drops.

daaam November 4th, 2019 01:08 PM

Quote:

Originally Posted by 99RT10>S (Post 4679397)
Check the ground strap near the front right side of the engine. If it is loose or disconnected, it could be causing the problem. I have heard it can cause problems with the oil cooler lines too.

This was disconnected and I reconnected it but I still had the same problem except when first starting up car it charges at 14.55 instead of 14.3 volts and drops from that point like before.

99RT10&GTS November 4th, 2019 01:37 PM

Quote:

Originally Posted by daaam (Post 4683983)
This was disconnected and I reconnected it but I still had the same problem except when first starting up car it charges at 14.55 instead of 14.3 volts and drops from that point like before.

I assume you cleaned/sanded the ground point good? There is another ground behind the front left wheel too. Clean it off and re-attach

daaam November 4th, 2019 01:40 PM

Quote:

Originally Posted by 99RT10>S (Post 4683985)
I assume you cleaned/sanded the ground point good? There is another ground behind the front left wheel too. Clean it off and re-attach

I have cleaned and cleaned and cleaned, LOL. I didn't see that ground as the only one I seen was the one on passenger side that connects kind of by the passenger side front wheel to the front of the engine block.

Lunchbox November 4th, 2019 03:18 PM

Quote:

Originally Posted by daaam (Post 4683977)
The 96RT-10's don't have the battery temp sensor. Thanks for the thought.

My bad, wasnt aware.

RobV November 4th, 2019 07:38 PM

Quote:

Originally Posted by daaam (Post 4683979)
I don't know how to measure the resistance....

what are you using to measure voltage?

CWhiteRun November 5th, 2019 09:53 AM

Don't take this the wrong way but if you do not know how to measure resistance then you really don't need to mess with the cars electrical system and you really should pay someone to troubleshoot for you. Also, the field control wire on the viper harness is not the field control wire on the alternator that viper uses.....it's done odd on viper. It would be in your best interest to tote it to a specialist.

daaam November 5th, 2019 04:27 PM

Quote:

Originally Posted by CWhiteRun (Post 4684103)
Don't take this the wrong way but if you do not know how to measure resistance then you really don't need to mess with the cars electrical system and you really should pay someone to troubleshoot for you. Also, the field control wire on the viper harness is not the field control wire on the alternator that viper uses.....it's done odd on viper. It would be in your best interest to tote it to a specialist.

What is the worst thing that happens if I don't measure resistance?????? Is my car going to blow up? am I going to get electrocuted and die? Nope, none of that. I would just be chasing my tail a little bit more and possibly trying things that may not need to be done, but does it really hurt anything? You really think that not being able to measure resistance is that imperative that I can't attempt to troubleshoot an electrical problem? I have troubleshooted every single electrical issue I have had for the last 20 years with no problems. This is actually the first time that I have struggled with a 12v electrical issue which is why I brought it up on the forums.

Most people are not experts and can work on things adequately, correctly and safely and this includes troubleshooting issues with my cars electrical system. I have above the basic understanding of how to wire 12 volt sources and have been doing it for over 20 years with zero issues thus far (I have had zero problems from my troubleshooting so far and I may have even figured out the issue). If I am getting the exact same results with brand new, larger wire of similar length that is directly wired from alternator to the battery without heat soak being an issue then resistance in that wire is not the issue and I can rule out that wire being an issue. I believe I would kind of be measuring resistance by checking the voltage output on alternator post compared to output showing at the battery and at the 12v post under hood? The larger the voltage drop the more resistance that may be being created?

It also just so happens that I did go to a professional and explained every test I did and they literally told me that is exactly what they would have done (but I guess I should have paid them $80.00 - $100.00 an hour to do the same tests) and then learn nothing in the process? They are very stumped as well on the issue and all they do for a living is electrical work dealing specifically with starters, alternators, etc...

I have the shop manuals that a technician would use for my car, I know which wires does what as it is outlined in the shop manual. My alternator has an internal regulator which is different from the gen 2's which are controlled by the PCM. I knew which wire was my sense wire by looking at the shop manual. I do appreciate you bringing up the issue with how the field wire is different on a Viper as that is the input I am looking for, not told to just bring it somewhere because you know how to check resistance and I don't. Now if I could get killed by not checking resistance you may be right to refer me to a professional.

Instead of insulting me, you could have just told me how to check resistance. I like to work on my own vehicle's and I come here for help on fixing my problems. I can't think of how useless forums would be if everyone's answer was to take something to the shop, as lots of people learn on the forums by doing things that they haven't done before. If I wanted to bring my car to someone to fix I would but I would rather learn and save my money.

Electrical issues are actually probably one of the last things you want to take to a shop as they can be some of the most costly repairs as the troubleshooting can be extensive, taking a lot of time to find the issue which transfers to being very expensive.

daaam November 5th, 2019 04:31 PM

Quote:

Originally Posted by RobV (Post 4684017)
what are you using to measure voltage?

2 separate digital multi meters. I use two to verify that my results I am measuring are accurate. The results always seem to be within .01 volts of each other so I am assuming they are accurate, and it reflects similar on my voltage gauge in my car (i don't rely on the car gauge as it seems to read slightly lower than my multi meters and its not precise enough)

AJ02 November 6th, 2019 04:35 PM

To measure resistance, all you have to do is set your multi-meter on one of the settings with the symbol that looks like a modified horseshoe. ( OHMS ) Measure from one end of a wire or circuit to the other and the reading will be the amount of resistance.

daaam November 8th, 2019 09:53 AM

Quote:

Originally Posted by AJ02 (Post 4684271)
To measure resistance, all you have to do is set your multi-meter on one of the settings with the symbol that looks like a modified horseshoe. ( OHMS ) Measure from one end of a wire or circuit to the other and the reading will be the amount of resistance.

Thanks so much! I will try this, this weekend. I assume I will have to do this when the wire is cold. Then check when the wire is hot, and check when car is running?

jslimm November 8th, 2019 07:06 PM

Quote:

Originally Posted by daaam (Post 4684471)
Thanks so much! I will try this, this weekend. I assume I will have to do this when the wire is cold. Then check when the wire is hot, and check when car is running?

You can't check resistance when there is a voltage applied to the thing you are checking.(well, not totally correct; but, you have to know what you are doing)
There has to be no voltage applied so that no current is running through it. Typically you would want at least one of the endpoints disconnected so that you are not measuring the resistance of more things in the circuit than you intend to measure (and that also ensures that no current is flowing in the thing you are measuring.)


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