what am i missing.im working on my ot.motorhome that i am taking to the races in two weeks.its a 74 c30 midas with a chevy 350.the alt was bad so i went up to advanced and got a new one.put it on and the mechanical gage reads 12volts.the idiot light is on.thought the alt was bad so i took it back and had them check it and it was good.put it back in and same problem.the alt has a field and another wire then the main battery out.both of the small wires have 12v when the key is on.the alt goes to a seperator for the rear battery.if i take my multi-meter the alt is putting out over 25volts?WTF!!!!disconect the wire from the seperator and the alt.is putting out 46volts AGAIN WTF!!!!tryed different multi-meter,same reading.pulled alt.out took to napa to have them check it it tests fine.if i back probe the two wires one is at 12.2 volts the other is at 19 or so.what an i doing wrong?????
Diagnosis of a camper system is not easy online First off, I am questioning the 24 and 56 volts. I have seen an internally shorted battery causing extra volts, but never reaching 20v Any chance you have an old analog gauge? either a tester or an old SW dash unit? Also, I would be finding a way to completely disable the backup battery system and just work on the trucks original elect system. I do volt tests at the battery, not at the alt. Should be 12.5 not running and around 14 running. As I recall on the first generation Delco w/internal reg, one small wire needs to be batt voltage, and the other is an exciter. Seems like you should pull the two wire plug off and test the wires disconnected? You need to start with basics.
i did take the wires that went to the rear battery and disconect them{there were two per.so i used a bolt and nut}if i pull the two wire plug off the alt.one has 12+volts and the other one only has power when the key is on.the motorhome has an idiot light and last year i put a mechanical gage in it.at the battery its not reading anything more than batt.volt.i wish it was at 14.7 at batt.i know there is something that im missing but maybe i just need to sit back and have a beer!!!!!!
Who knows what Midas Motorhome did to the orig GM main harness??? Here's a thought; maybe they put an inline fusible link buried under the hood someplace...a link like Mopars all had. Just to try; maybe run a 10 gauge jumper from the main alt output, and run it to the trucks positive battery post? well, if not, then btt
i was thinking about just jumping the one bigger wire to the battery and leaving the other wire{idiot light?}wire un hooked.will this drain the battery?or over heat the alt when its not running?
i'm not clear on what you mean, but... I'd run a test jumper from the big alt terminal to the trucks main battery positive post...just to test. Let's say there was a bad connection in that line somewhere that can't take the amps to the battery... a jumper would tell someting "if" it now is getting 14+ to the main battery. If you don't have a heavy jumper wire, you can just momentarily touch a smaller test wire to the alt. If it sparks at all, there is a problem in the main charging "loop" wiring. The problem with redesigning GM's wiring, is that likely something else won't work right.,, like idiot light or feedback etc On Chevy pickup trucks of that age, there was a black terminal block on the firewall and maybe another near the fender/battery area. What I am saying is there may be a few places that could have a bad connection in that main charging wire. If the test jumper works, then you back track from alt and battery to find the problem. btt again
i took the main wire off the alt.{at the isolator}when the motor is running and the wire is disconected its reading 46 volts.i checked it with two different multi-meters.i dont care if the idiot light doesnt work because i look at my gages all the time.i just want it to charge and not blow up the battery.if i had some more money and didnt just use it two to three times ayear i would spend the $100 and put a single wire alt.from summit in it.the new one only cost me $28.00 put i have over 5 hours in it and its still fd up!!!im at a loss here now and just want to figure it out.
If you are testing the alternator main terminal while disconnected...I ask WHY ?? Alternators are fully capable of running 120v power tools if you know how to do it Did you humor me and run a jumper yet? Anyways, pleeeeeeze run a jumper from alt main feed to batt +, then do volt test at the batt..not the alt
You probably need a alternator that puts out 100 amp or 140 amp that stock one puts out about 63 amps, The camper is proably using up everything the stock puts out .
i thought about that but im not useing any of the 12v appl.in it.when i get to the track either i hook up to there power or i start up my gen.and use it.the only thing that i use is the 12v waterpump,and thats just to clean dishes and fill the coffe pot.
sounds to me like the output wire from the alt. is broken between bat. with that wire disconnected the regulator wont see the bat. voltage and will keep upping the voltage output.
I know this sounds stupid but, did you check the water in your battery. My bucket was acting up amp needel all over the place checked all the wires had the alt. checked couldn't get it to charge the battery and hold a charge, popped the battery caps no water, just saying.
does the alt have a regulator on it ? is it a 3 wire alt ? sounds like your missing the regulator somehow .
First off, don't trust the Advanced auto parts testers. I just went a round with that. They are generally useless. They turn at a very slow rpm. My alternator showed good at slow speed but was shorting out when used at operating speeds. You can leave the wire for the idiot light disconnected. I agree with the above and keeping it simple. Do your checks at the battery. The only tests I do at the alternator is to make sure that it's getting power and ground. Start over with the basics. Check for proper power to the alternator and then ground. Then do your checks at the alternator. If you have disconnected the aux battery and have power to the alternator (and ground) and you still are not charging, it almost still has to be a bad alternator. I don't bother buying the crappy rebuilt Chinese stuff the big guys sell. I take it to the quality rebuilder here in town. Yep, I have to pay for that but he diagnosed the short right off where Advance missed it and it was fixed right the first time.
I have never heard of such high voltages from an alternator......are you testing it with the battery disconnected? No load on alt. will give a very high reading and most likely cook it. Whenever installing a new alt., ALWAYS charge the battery first, otherwise you may cook the new alt. The idea is to test the voltage across the battery terminals, not at the alternator. Early GM alternators have a "D" shaped hole in the back of the housing, if you put a small screwdriver across the edge of the D hole and touch the bottom of the hole with, you can full field the alt. This bypasses the regulator(essentially) and should give about 15-16volts. What meters have you used analog(numbers, with a needle that moves) or digital(electronic numbers that have no needle). Digital is the way to go, auto-ranging meters are best, 'cause pick the right voltage for ya. I suspect that you may be using an analog meter either on the wrong range or are mis-reading the scale.(Done it myself, a few times). So to re-cap: -charge the battery first -Make sure you have good connections all around -get a digital meter $15-20 for cheapo, $50 for a nice one the has automotive functions, like dwell, etc. -now report back, and let us know how you made out Electricals don't have to be scary or frustrating, once some basic stuff has gone through. I used work at a Ford dealer in England, and most of the mechanics were electrical-shy, and used call in outside auto electrician before they even checked fuses!
"There were two per so I used a bolt and nut".....Huh? you got some 'splainen to do, Lucy! Sounds like you shorted them out!
on the rear battery{which runs the appl.}there is a power comming in and one going to the rear fuse panel.if the wires are dicconected from the battery nothing works except the main truck electric.
thanks everyone for helping.after several more hours of checking wires and jumping wires i have it working.im still not sure whats wrong but i think the isolator is bad.on the isolator there are three lugs.left one goes to the rear battery,the center one is power from the alt. and the right one goes to the starter{which i guess will charge the front battery}.if i jumped the center wire to the front battery 14.5v.if i jumped the right one to the center 14.5v.so what i did was dicsonect the right wire{starter}and hook it up to the center{alt.}.the only thing i dont like is now the rear isint sep.from the front.so if someone leaves the lights or water pump on it will also draw from the front {engine starting battery}.i dont think this will be a problem but i might put a batt.shut-off in it so it wont drain the main battery.
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