electrical ? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

PR454SS · 02-09-2004, 03:15 PM

Here is one for the electrical wizzards, I found out the hard way that altenators don't like a motor that spins to 7500 rpm. I burned up the bearings in one last week, I figured no big deal, replaced it with a rebuilt one from Advance Auto Parts,
I drove it home and just out curiosity I pulled the neg cable off the battery, truck died, I have replaced the altenator and the voltage regulator with spares I had and I still have the same problem. The thing will run on the battery but it is not charging.
I think the wiring on the truck is about to go

any help would be great. Thanks, Paul

**CPNE** · 02-09-2004, 03:22 PM

Correct me if i'm wrong, but if you remove you battery ground aren't you interrupting the circuit thats required for DC to work?

PR454SS · 02-09-2004, 03:24 PM

But I think it should run off the altenator, but then again I do have C.R.S.
(can't remember sh**)

**CPNE** · 02-09-2004, 03:31 PM

I don't think so, DC requires a ground. You've interupted this "loop" when you disconnect the negative cable.

PR454SS · 02-09-2004, 03:36 PM

now I'm not sure how to check the thing
the idiot light isn't on but it killed the battery when I drove it last time???

BUXMAN66 · 02-09-2004, 03:38 PM

the age-old way to tell if your alt. is bad....? take off the neg. cbl. off the batt......that tells you it was strictly running off of juice from the battery. it never has failed me......

71Rat · 02-09-2004, 04:29 PM

yup you can take the neg side off of the batt. and if the engine dies the alt is bad...... DON"T TRY THIS WITH A CAR WITH A COMPUTER!!!! the computer will be burnt up fast... the batt. controls voltage spikes and without it they go to the ECU and kill it

Rat

**CPNE** · 02-09-2004, 04:33 PM

Not sure what I was thinking here.

Guess I wasn't

PR454SS · 02-10-2004, 04:52 AM

so given the details what do you guys think is wrong?

krue · 02-10-2004, 05:35 AM

Try to find an auto electric shop local to you and have your old alternator rebuilt. Around here you can get it done for what a cheap az alternator would cost and know it was done right.

FirstGen · 02-10-2004, 12:36 PM

Personally, sounds like you have a wiring problem. I doubt if a brand new alternator no matter how cheap wouldn't work at all. You can also take a volt meter and measure the amperage and or voltage across it to see if it is putting anything out.
My advise: $75 and you can get a brand new factory engine wiring harness, you will spend that real quick getting someone to look at it and tell you that you need to re-wire it

PR454SS · 02-10-2004, 02:35 PM

I think I might try to check it with a meter and I might as well upgrade the wiring and guage cluster while I'm at it. Do the vendors have new harnesses or do I need to find one local?

FirstGen · 02-10-2004, 03:13 PM

The underdash wiring harness is quite pricy new, about 250 but check ebay I just bought a really nice used one for $25 bucks and I saw the same user was selling several more afterwards (this was last week).

Check Ricks for the motor harness it's $75 new....

Hope that helps alittle.

PR454SS · 02-10-2004, 03:15 PM

It sure did help thanks for the info.

tom hand · 02-10-2004, 03:22 PM

Removing the battery cable is a test left over from when cars had generators....it is far from foolproof with an alternator. The field circuit in an alternator requires voltage for it to charge and a voltage spike could turn the alternator off. A much better "redneck" test is to hold a screwdriver to the metal cap on the back of the alternator while the engine is running...if it has a strong magnetic pull the alternator is charging

PR454SS · 02-10-2004, 04:20 PM

Well I didn't get any magnetic pull using a small screwdriver for better feel, so I guess it's bad. I had never heard of that test before but it makes perfect sense.
Thanks

FirstGen · 02-10-2004, 05:31 PM

Just a note, make sure you replace the voltage regulator at the same time always. These work in unison and can trip you up when trying to troubleshoot charging systems...

I'd still be very surprised if your "new" alternator is faulty. I would check your ammeter before taking it back or whatever. Redneck tricks are only as good as they are called

your meter won't lie to you!

krazy_texan · 02-10-2004, 05:55 PM

i had that problem in my 71 a while back, replaced the harness and the problem went away.

A.P. · 02-10-2004, 06:11 PM

PR454SS
I second with what "FirstGen" said. Replace the voltage regulator with a new one. If you are still having problems and think its the wires, try tracing them. Here is the diagrams.

http://www.geocities.com/chevroletc1070/wiringdias.html

PR454SS · 02-10-2004, 06:16 PM

I have replaced both and it still is not charging that seems to be the problem, But I wouldn't know why it would do it after I replaced the altenator.

FirstGen · 02-10-2004, 06:40 PM

If you did not replace them at the same time that could be your problem. One can directly effect (damage) the other. If you did do this better look for a harness or start trouble shooting

Good Luck!

SWEET7T · 02-10-2004, 08:32 PM

I know I have a good alt, but I would guess that the ammeters would make a pretty smooth movement. 80% of the time mine is bouncy (constant jiggle like a nervous chihuahua), it will stay over in the charge area (has never moved passed half way to pegged but then I don't expect it to unless I really drain the batt). When the truck is off, I can turn heater & lights on and it shows a discharge without jiggle. Would this be a voltage reg problem (or could cause it) or do I just have a loose wire somewhere?!

Thanks for the help.

The best way to test your alt is to take it to a shop and have them run it on their tester. As for you turning your engine at 7500rpm, maybe you should change your pulley(s) to change the drive ratio so you don't spin the alt so fast! But then you loose charging power at low/idle rpms. Good luck with it!

PR454SS · 02-10-2004, 10:41 PM

Ya I've got a large diameter pulley just burned it up before I swapped it, my truck doesn't have a gauge , but on my 69 there was a jiggle in the gauge and it turned out to be the wire for the temp sending unit shorting out, I think it should show a constant charge or discharge. Good luck

02-09-2004, 03:15 PM	#1
PR454SS Registered User Join Date: Aug 2003 Location: Louisville, TN Posts: 338	electrical ? Here is one for the electrical wizzards, I found out the hard way that altenators don't like a motor that spins to 7500 rpm. I burned up the bearings in one last week, I figured no big deal, replaced it with a rebuilt one from Advance Auto Parts, I drove it home and just out curiosity I pulled the neg cable off the battery, truck died, I have replaced the altenator and the voltage regulator with spares I had and I still have the same problem. The thing will run on the battery but it is not charging. I think the wiring on the truck is about to go any help would be great. Thanks, Paul __________________ PR Too many projects, not enough time! 72SWB 350/350TH, 3500stall,525 lift cam 3:73 posi. Sold! 69LWB Flatbed 350/Super T-10, ported/polished 481 heads, 480 lift cam. 78SWB 468/400TH, ported/polished Alum. heads, 3:42 posi, 3000 stall on 17x8 and 18x9.5's 77 Jeep CJ-5 304V8 fiberglass body on 36" Ground Hawgs

02-09-2004, 03:22 PM	#2
CPNE Resident Curmudgeon Join Date: Dec 1999 Location: NH Posts: 6,662	Correct me if i'm wrong, but if you remove you battery ground aren't you interrupting the circuit thats required for DC to work? __________________ Currently on or near the homestead: 67 Chevy SWB 2WD stepside 350/3 on tree (Pat's) 67 GMC SWB 2WD Fleet 402/auto (Brian's under construction) 67 Chevy 3/4 ton 2WD 402/auto (Business Hauler) 67 Chevy 1 ton dually 2WD 396/4 speed (Former business hauler, Needs TLC) 68 Chevy 1/2 ton Suburban 2WD 250 six/3 on tree (Brian's Needs TLC) 70 Chevy 3/4 ton 4WD 350/4 speed (Pat's - Disguised as a 68 GMC) 71 Chevy SWB stepside (Crushed by tree - parts donor) 72 Chevy 3/4 ton 4WD (Parts donor) 72 Chevy 3/4 ton 4WD Suburban (Parts Donor) 72 GMC 3/4 ton 4WD 292 six/4 speed (Mine - Disguised as a 67 GMC) 81 GMC 4WD Dually Dump Body 350/4 speed (Business Hauler) 82 Camaro Z/28 355/Super T-10 (Pat's toy) 93 Caprice 9C1 (Brian's Cop Car) 02 Toyota Camry (Reliable but a souless steel and plastic hulk) 2011 2SS RS Camaro M6 Factory Hurst Shifter Maybe I need to sell some of this crap Yet another Bozo with a sawz-all

02-09-2004, 03:24 PM	#3
PR454SS Registered User Join Date: Aug 2003 Location: Louisville, TN Posts: 338	But I think it should run off the altenator, but then again I do have C.R.S. (can't remember sh**) __________________ PR Too many projects, not enough time! 72SWB 350/350TH, 3500stall,525 lift cam 3:73 posi. Sold! 69LWB Flatbed 350/Super T-10, ported/polished 481 heads, 480 lift cam. 78SWB 468/400TH, ported/polished Alum. heads, 3:42 posi, 3000 stall on 17x8 and 18x9.5's 77 Jeep CJ-5 304V8 fiberglass body on 36" Ground Hawgs

02-09-2004, 03:31 PM	#4
CPNE Resident Curmudgeon Join Date: Dec 1999 Location: NH Posts: 6,662	I don't think so, DC requires a ground. You've interupted this "loop" when you disconnect the negative cable. __________________ Currently on or near the homestead: 67 Chevy SWB 2WD stepside 350/3 on tree (Pat's) 67 GMC SWB 2WD Fleet 402/auto (Brian's under construction) 67 Chevy 3/4 ton 2WD 402/auto (Business Hauler) 67 Chevy 1 ton dually 2WD 396/4 speed (Former business hauler, Needs TLC) 68 Chevy 1/2 ton Suburban 2WD 250 six/3 on tree (Brian's Needs TLC) 70 Chevy 3/4 ton 4WD 350/4 speed (Pat's - Disguised as a 68 GMC) 71 Chevy SWB stepside (Crushed by tree - parts donor) 72 Chevy 3/4 ton 4WD (Parts donor) 72 Chevy 3/4 ton 4WD Suburban (Parts Donor) 72 GMC 3/4 ton 4WD 292 six/4 speed (Mine - Disguised as a 67 GMC) 81 GMC 4WD Dually Dump Body 350/4 speed (Business Hauler) 82 Camaro Z/28 355/Super T-10 (Pat's toy) 93 Caprice 9C1 (Brian's Cop Car) 02 Toyota Camry (Reliable but a souless steel and plastic hulk) 2011 2SS RS Camaro M6 Factory Hurst Shifter Maybe I need to sell some of this crap Yet another Bozo with a sawz-all

02-09-2004, 03:36 PM	#5
PR454SS Registered User Join Date: Aug 2003 Location: Louisville, TN Posts: 338	now I'm not sure how to check the thing the idiot light isn't on but it killed the battery when I drove it last time??? __________________ PR Too many projects, not enough time! 72SWB 350/350TH, 3500stall,525 lift cam 3:73 posi. Sold! 69LWB Flatbed 350/Super T-10, ported/polished 481 heads, 480 lift cam. 78SWB 468/400TH, ported/polished Alum. heads, 3:42 posi, 3000 stall on 17x8 and 18x9.5's 77 Jeep CJ-5 304V8 fiberglass body on 36" Ground Hawgs

02-09-2004, 03:38 PM	#6
BUXMAN66 go bucks! Join Date: Jan 2002 Location: MIAMISBURG OHIO USA Posts: 803	the age-old way to tell if your alt. is bad....? take off the neg. cbl. off the batt......that tells you it was strictly running off of juice from the battery. it never has failed me...... __________________ '68 swb 1/2t 350/350th '86 lngbd 3/4 TON parts getter '49 gmc 1/2 t 5 window 350/350th '96 gmc sonoma sle ext-cab. hey it's a 4cyl. 5 spd and good on gas y'know?

02-09-2004, 04:29 PM	#7
71Rat ran out of money Join Date: Apr 2003 Location: northern, NJ Posts: 925	yup you can take the neg side off of the batt. and if the engine dies the alt is bad...... DON"T TRY THIS WITH A CAR WITH A COMPUTER!!!! the computer will be burnt up fast... the batt. controls voltage spikes and without it they go to the ECU and kill it Rat __________________ Modify everything, leave nothing alone!~

02-09-2004, 04:33 PM	#8
CPNE Resident Curmudgeon Join Date: Dec 1999 Location: NH Posts: 6,662	Not sure what I was thinking here. Guess I wasn't __________________ Currently on or near the homestead: 67 Chevy SWB 2WD stepside 350/3 on tree (Pat's) 67 GMC SWB 2WD Fleet 402/auto (Brian's under construction) 67 Chevy 3/4 ton 2WD 402/auto (Business Hauler) 67 Chevy 1 ton dually 2WD 396/4 speed (Former business hauler, Needs TLC) 68 Chevy 1/2 ton Suburban 2WD 250 six/3 on tree (Brian's Needs TLC) 70 Chevy 3/4 ton 4WD 350/4 speed (Pat's - Disguised as a 68 GMC) 71 Chevy SWB stepside (Crushed by tree - parts donor) 72 Chevy 3/4 ton 4WD (Parts donor) 72 Chevy 3/4 ton 4WD Suburban (Parts Donor) 72 GMC 3/4 ton 4WD 292 six/4 speed (Mine - Disguised as a 67 GMC) 81 GMC 4WD Dually Dump Body 350/4 speed (Business Hauler) 82 Camaro Z/28 355/Super T-10 (Pat's toy) 93 Caprice 9C1 (Brian's Cop Car) 02 Toyota Camry (Reliable but a souless steel and plastic hulk) 2011 2SS RS Camaro M6 Factory Hurst Shifter Maybe I need to sell some of this crap Yet another Bozo with a sawz-all

02-10-2004, 04:52 AM	#9
PR454SS Registered User Join Date: Aug 2003 Location: Louisville, TN Posts: 338	so given the details what do you guys think is wrong? __________________ PR Too many projects, not enough time! 72SWB 350/350TH, 3500stall,525 lift cam 3:73 posi. Sold! 69LWB Flatbed 350/Super T-10, ported/polished 481 heads, 480 lift cam. 78SWB 468/400TH, ported/polished Alum. heads, 3:42 posi, 3000 stall on 17x8 and 18x9.5's 77 Jeep CJ-5 304V8 fiberglass body on 36" Ground Hawgs

02-10-2004, 05:35 AM	#10
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,448	Try to find an auto electric shop local to you and have your old alternator rebuilt. Around here you can get it done for what a cheap az alternator would cost and know it was done right. __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"

02-10-2004, 12:36 PM	#11
FirstGen Just Don't Stop! Join Date: Feb 2004 Location: Dallas Posts: 1,239	Personally, sounds like you have a wiring problem. I doubt if a brand new alternator no matter how cheap wouldn't work at all. You can also take a volt meter and measure the amperage and or voltage across it to see if it is putting anything out. My advise: $75 and you can get a brand new factory engine wiring harness, you will spend that real quick getting someone to look at it and tell you that you need to re-wire it __________________ 1968 C10 build in process TT LSA/6L90e/9"

02-10-2004, 02:35 PM	#12
PR454SS Registered User Join Date: Aug 2003 Location: Louisville, TN Posts: 338	I think I might try to check it with a meter and I might as well upgrade the wiring and guage cluster while I'm at it. Do the vendors have new harnesses or do I need to find one local? __________________ PR Too many projects, not enough time! 72SWB 350/350TH, 3500stall,525 lift cam 3:73 posi. Sold! 69LWB Flatbed 350/Super T-10, ported/polished 481 heads, 480 lift cam. 78SWB 468/400TH, ported/polished Alum. heads, 3:42 posi, 3000 stall on 17x8 and 18x9.5's 77 Jeep CJ-5 304V8 fiberglass body on 36" Ground Hawgs

02-10-2004, 03:13 PM	#13
FirstGen Just Don't Stop! Join Date: Feb 2004 Location: Dallas Posts: 1,239	The underdash wiring harness is quite pricy new, about 250 but check ebay I just bought a really nice used one for $25 bucks and I saw the same user was selling several more afterwards (this was last week). Check Ricks for the motor harness it's $75 new.... Hope that helps alittle. __________________ 1968 C10 build in process TT LSA/6L90e/9"

02-10-2004, 03:15 PM	#14
PR454SS Registered User Join Date: Aug 2003 Location: Louisville, TN Posts: 338	It sure did help thanks for the info. __________________ PR Too many projects, not enough time! 72SWB 350/350TH, 3500stall,525 lift cam 3:73 posi. Sold! 69LWB Flatbed 350/Super T-10, ported/polished 481 heads, 480 lift cam. 78SWB 468/400TH, ported/polished Alum. heads, 3:42 posi, 3000 stall on 17x8 and 18x9.5's 77 Jeep CJ-5 304V8 fiberglass body on 36" Ground Hawgs

02-10-2004, 03:22 PM	#15
tom hand CCRider Join Date: Feb 2000 Location: Olive Branch,MS,USA Posts: 2,232	Removing the battery cable is a test left over from when cars had generators....it is far from foolproof with an alternator. The field circuit in an alternator requires voltage for it to charge and a voltage spike could turn the alternator off. A much better "redneck" test is to hold a screwdriver to the metal cap on the back of the alternator while the engine is running...if it has a strong magnetic pull the alternator is charging __________________ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS



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02-10-2004, 04:20 PM	#16
PR454SS Registered User Join Date: Aug 2003 Location: Louisville, TN Posts: 338	Well I didn't get any magnetic pull using a small screwdriver for better feel, so I guess it's bad. I had never heard of that test before but it makes perfect sense. Thanks __________________ PR Too many projects, not enough time! 72SWB 350/350TH, 3500stall,525 lift cam 3:73 posi. Sold! 69LWB Flatbed 350/Super T-10, ported/polished 481 heads, 480 lift cam. 78SWB 468/400TH, ported/polished Alum. heads, 3:42 posi, 3000 stall on 17x8 and 18x9.5's 77 Jeep CJ-5 304V8 fiberglass body on 36" Ground Hawgs

02-10-2004, 05:31 PM	#17
FirstGen Just Don't Stop! Join Date: Feb 2004 Location: Dallas Posts: 1,239	Just a note, make sure you replace the voltage regulator at the same time always. These work in unison and can trip you up when trying to troubleshoot charging systems... I'd still be very surprised if your "new" alternator is faulty. I would check your ammeter before taking it back or whatever. Redneck tricks are only as good as they are called your meter won't lie to you! __________________ 1968 C10 build in process TT LSA/6L90e/9"

02-10-2004, 05:55 PM	#18
krazy_texan Registered User Join Date: Oct 2002 Location: West Des Moines, Ia Posts: 3,233	i had that problem in my 71 a while back, replaced the harness and the problem went away. __________________ Krazy Texan My Trucks are made with Wrenches not Chop Sticks 1967 GMC 3/4 ton "Johnny Cash" 1990 v1500 suburban 1967 Ford f100 Swb 4x4 "green bean" GOD BLESS JESUS, JOHN WAYNE, AND THE ALAMO

02-10-2004, 06:11 PM	#19
A.P. Black 72 Chevy Join Date: May 2002 Location: Los Angeles, California Posts: 662	PR454SS I second with what "FirstGen" said. Replace the voltage regulator with a new one. If you are still having problems and think its the wires, try tracing them. Here is the diagrams. http://www.geocities.com/chevroletc1070/wiringdias.html

02-10-2004, 06:16 PM	#20
PR454SS Registered User Join Date: Aug 2003 Location: Louisville, TN Posts: 338	I have replaced both and it still is not charging that seems to be the problem, But I wouldn't know why it would do it after I replaced the altenator. __________________ PR Too many projects, not enough time! 72SWB 350/350TH, 3500stall,525 lift cam 3:73 posi. Sold! 69LWB Flatbed 350/Super T-10, ported/polished 481 heads, 480 lift cam. 78SWB 468/400TH, ported/polished Alum. heads, 3:42 posi, 3000 stall on 17x8 and 18x9.5's 77 Jeep CJ-5 304V8 fiberglass body on 36" Ground Hawgs

02-10-2004, 06:40 PM	#21
FirstGen Just Don't Stop! Join Date: Feb 2004 Location: Dallas Posts: 1,239	If you did not replace them at the same time that could be your problem. One can directly effect (damage) the other. If you did do this better look for a harness or start trouble shooting Good Luck! __________________ 1968 C10 build in process TT LSA/6L90e/9"

02-10-2004, 08:32 PM	#22
SWEET7T Try spinnin 4 rear tars Join Date: Sep 2003 Location: Salt Lake City, Utah Posts: 757	not to hijack but is on kinda on topic I know I have a good alt, but I would guess that the ammeters would make a pretty smooth movement. 80% of the time mine is bouncy (constant jiggle like a nervous chihuahua), it will stay over in the charge area (has never moved passed half way to pegged but then I don't expect it to unless I really drain the batt). When the truck is off, I can turn heater & lights on and it shows a discharge without jiggle. Would this be a voltage reg problem (or could cause it) or do I just have a loose wire somewhere?! Thanks for the help. The best way to test your alt is to take it to a shop and have them run it on their tester. As for you turning your engine at 7500rpm, maybe you should change your pulley(s) to change the drive ratio so you don't spin the alt so fast! But then you loose charging power at low/idle rpms. Good luck with it! __________________ SWEET7T 1970 C10, 2wd, LB, 307/TH350/3.08. PS, PB

02-10-2004, 10:41 PM	#23
PR454SS Registered User Join Date: Aug 2003 Location: Louisville, TN Posts: 338	Ya I've got a large diameter pulley just burned it up before I swapped it, my truck doesn't have a gauge , but on my 69 there was a jiggle in the gauge and it turned out to be the wire for the temp sending unit shorting out, I think it should show a constant charge or discharge. Good luck __________________ PR Too many projects, not enough time! 72SWB 350/350TH, 3500stall,525 lift cam 3:73 posi. Sold! 69LWB Flatbed 350/Super T-10, ported/polished 481 heads, 480 lift cam. 78SWB 468/400TH, ported/polished Alum. heads, 3:42 posi, 3000 stall on 17x8 and 18x9.5's 77 Jeep CJ-5 304V8 fiberglass body on 36" Ground Hawgs

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