97grand4.0

If you get charging voltage at the battery, then the vehicle is charging ok. Make sure you are reading right at the battery posts, not the terminals. This also means your alternator is putting something out.
I would still take it in for a free check up at AZ or somewhere, maybe a bad diode, I know you said it's a new alt.

0 volts on the dash, well, I am not sure on this, maybe someone knows if there is a fuse in play there, you could have blown with the 18v? When you get an overvoltage like that, everything in the car is at risk of toasting.
That said, just take a careful and thorough look with a good flashlight at all the visible wiring, check for anything foul looking, chaffed, bare, two wires touching that shouldnt, crawl under and look at the 2 field wires on the Alternator connection..sure you did that when you changed the alt..also check the batt terminal on the alt...

alg

thanks, I will do a good check of all of that, I did check the voltage with and without the alt in cir. at the batt. with out the alt in I get 12 to 3 v with it in cir I getr about 15 or a little less. so I do know its getting from a to b. voltage that is. I will look for as you suggest all wires and connectors. This by the way was the reason in the fist place I started to look at the alt. cause I noticed that the gauge had no reading. Could the gauge itself fried during all this high voltage? or dose its source come form pcm.

alg

thats 12 to 13 volts typo

dave1123

ALL the gauges come off the PCM bus, that is wiring that comes directly from the PCM. It's possible the voltmeter is fried. Try taking volt readings from the top of the fuses.

alg

well I am at a complete loss. this problem continues on. I came back from a few days away. B/4 I left the car ran correctly other than the voltage gauge not showing any reading. but all was good engine wise and charging correctly.
I stated the car and poof the same thing happens. I disconnect the control wire from the alt. and all is good again. I have the battery temp sensor out. and with it in or out the same thing happens. I am waiting on the new sensor but at this point I don't think this is going to do it.
why would the problem come back all on its own. with out the car being started for a few days? I am thinking pcm at this point?
help anyone out there.

alg

I also checked for any wiring problems, frayed broken, disconnected and all are good to the eye

alg

also, volt meter on dash moves ever so slightly. it dose not indicate the proper voltage, I see on the battery post 14 to 15 vdc when it was working correctly. with the control wire disco from the alt i see no movement at all at the gauge.

97grand4.0

So last I knew you were going to order a new batt temp sensor, for that matter, go get one at the junk yard for $3 as a stop gap. Also you should include voltages from your test meter. IF and I say IF your new sensor doesn't do the trick, I would indeed say the regulator MAY be fried in the pcm, even so, there are cheaper work arounds for that involving putting in a regulator from an older dodge truck.
Are you sure your paper clip is in and connecting? hope that helps.

alg

I am expecting the new sensor sometime today. upon installing it it will be revealed if its the sensor or not. My take at this point is not. Yes the paper clip is in thats for sure. I disconnected the battery again for now. to see if that resets what ever? thats what I did the last time along with the paper clip. in or out. so upon getting the new sensor and installing it I will really know if its that or not. I will include voltage reading upon my next post. I know that at the connector at the rear of the alt It was 11.7 with it unplugged from the alt. and the output was 50v with its wire to the batt. disconnected. the battery post reading was 11.8. of course the engine is running but not being charged so there will be a voltage drop. I checked for a short cir. at the connector at the rear of the alt and no short. dont recall the reading in ohms will redo.

alg

i installed the new sensor. same thing happens. voltage readings are; with control wire connected at alt 19v with it disconnected 11.9. disconnected both wires at alt read 0v.
with positive wire disconnected and control wire connected 40v the plug which goes to the control at the rear of the alt. disconnected from the alt = 11.7. the moment I both wires are connected the engine losses power and the issue returned

97grand4.0

Yeah, some of these are just plain hard to diagnose without hands on, but if I had to guess....You did say new alternator and battery, right? Did you ever have the battery tested? A defective battery with an open cell might cause that.
Absent that I would guess the regulator in the pcm is fried. ( I do find it unusual that it would fail in the full output state, but certainly very possible) There are kits on Ebay I mentioned earler for bypassing it with a regulator from an older dodge truck, which looks to me like a perfectly good solution. OTher than that you are replacing the pcm: if it doesn't need to be flashed with your vin and mileage might be a workable solution also. Test that battery first. 11.9VDC resting battery voltage is indicative of a severely undercharged battery. Full charge is 12.6.

alg

Well at this point after I test the batt. as you suggest. I recon that PCM is the next in line for replacement. With the additional problem that the volt gauge is not reading I tend to think PCM is the culprit.

97grand4.0

PCM can run well north of $450 to get it all flashed up by the seller, ebay regulator kits are like $60. . I would also look into the voltage gauge not working right at the same time the regulator is telling the alt to max charge....I may dig into this a little for you..but that battery should be bench tested by a good tester or swap another one in, hate to say it but the alternator is also still suspect, advance can test it for free they have very good equipment

alg

I dont really want to just test a new pcm without knowing if thats the cause. I know its not cheap that's why I was replacing the less expensive stuff first. What I am really confused about is why prior to leaving for my mini vac. for a few days did it start and run right. then when I get back 4 days latter while no one started it. dose it go back to my original issue. this is the mystery. and now I cant get it to go good again doing the same things I did. I am a little concerned about doing the external reg. thinking that other things will start to rear its little head after doing that. So if I want to repair it right I have to get the pcm and hopefully be done with it I will pull both batt, and alt and go to advance have them checked. my gut says they are ok. but I've been wrong once in my life b/4 LOL thanks again for all you input. If you come up with something else please share.

97grand4.0

HUM. Just enough time for the battery to loose its surface charge. at 11.9 you are 40% charged. IF it's this way and you just took it off the charger, it's toast.