AMP Gague woes - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bmg · 03-25-2005, 05:53 PM

I am about to replece my circuit board on the dash and have a question about the amp gage. It is hard wired to that alternator can i just not hook that part of the circuit board up or will that screw the whole board from working properly. if not then just don't hook the hard wires back up on the back of the gage and tape em off.. just not sure what i need to do to make it work properly with the least chance of making a huge mess.

JimKshortstep4x4 · 03-25-2005, 08:44 PM

Since the factory ammeter runs off of very low power both wires are hooked to the main feed wire that goes to the cab. The ammeter reads the resistance power in the wire and is not connected to the alternator. It reads depending on which way power is flowing in the main feed. If you were to run alternator amperage through a stock ammeter it will fry the meter. The stock ammeter is protected by two small 4 amp fuses. If you disconnect the two connections or wires on the ammeter it will have no effect on the running, charging or the way other gauges work.

Jim

Robert1970C20rstbukt · 03-26-2005, 12:22 AM

By any chance are these wires y'all are talking about dark purple? There's an aftermarket amp gauge bolted to the bottom of the dash in my truck and it has two 10 gauge dark purple wires hooked to it. When I take off either one all the power inside the cab goes dead. Are these supposed to be hooked up to the stock ammeter in the dash or something? Not tryin to hijack the thread but I've been wondering about this for a long time.

jhow66 · 03-26-2005, 01:05 AM

Quote:

Originally Posted by Robert1970C20rstbukt

By any chance are these wires y'all are talking about dark purple? There's an aftermarket amp gauge bolted to the bottom of the dash in my truck and it has two 10 gauge dark purple wires hooked to it. When I take off either one all the power inside the cab goes dead. Are these supposed to be hooked up to the stock ammeter in the dash or something? Not tryin to hijack the thread but I've been wondering about this for a long time.

Will truck still run with one of the wires off. Your amp gauge is wired by cutting a main feed wire and putting the amp in between.

Robert1970C20rstbukt · 03-26-2005, 01:37 PM

Nope, when I pull either wire everything shuts down. Do those wires hook to the back of the factory amp gauge in the dash, even though the printed circuit is already there? I checked all the wiring and replaced both fuses in the harness and the factory one never worked.

Bob Moore · 03-26-2005, 01:42 PM

Robert - The only 10 ga. purple wires I am familiar with in the cab are normally attached to the neutral safety switch. Do you have an automatic or has someone switched harnesses? Are there wires to your N/S?

bmg · 03-26-2005, 03:04 PM

mine is hard wired from the back of the gage to: red wire directly to the alternator and blue wire goes to the voltage regulator that is bybassed.... so i am wondering if i don't hook these wires back up will the system still charge like its suppose to ............off the dash circuit board

Robert1970C20rstbukt · 03-26-2005, 05:09 PM

Bob- My truck was always an auto truck. I have checked the Neutral SS wires and they are uncut, all the way to the plug. I did have to unplug and jump the NSS because it's screwed up and it would shut the engine off with the tranny in any gear. The ones hooked to the aftermarket ammeter run through the firewall into the factory alternator/charging harness. They look dark purple but they could be black, it's really hard to tell what color they are while standing on your head.

If someone could post a wiring diagram it might help, I don't have any saved on my computer.

Old Dave · 03-26-2005, 05:25 PM

Found this link on an old post:http://www.geocities.com/chevroletc1070/wiringdias.html

**john** · 03-26-2005, 07:17 PM

Robert here are the factory wires. They are 18 ga. This guage will not handle any load. What you have is aftermarket wired so all your power runs through it. So to answer your question do not hook up to factory ga. or it will go poof. John

JimKshortstep4x4 · 03-26-2005, 07:49 PM

BMG,

I am assuming that you have an after market gauge which is wired very different from stock. The stock gauge picks up current from the wire resistance and can only be used for this kind of hook up. As someone said if you hook it up direct it will go "poof". What you probably have is an aftermarket gauge that is connected to the alternator in such a way that all current flows through the gauge. Depending on how it is wired it could shut off everything. I would recommend that you check it carefully. Since the total current is flowing through the gauge it must be designed to take the full current or the gauge will blow.

I shy away from full amperage gauges because of the potential shorts. That is a lot of power that flows into your cab and back out again.

Jim

Robert1970C20rstbukt · 03-27-2005, 12:16 AM

John thanks for posting the pic, even though I forgot I have both of the '70 service and overhaul manuals with the diagrams in 'em.

I traced the black white striped wire and i'm getting power through it, but the ammeter just sits there when I turn the key on and start the truck. Does anybody know an easy way to check the original ammeter to see if it is still good?

Hey bmg again i'm sorry I wasn't trying to hijack the thread, I just read it and I started thinking wtf is wrong with the one in my truck.

ddsmith · 03-27-2005, 12:38 AM

An easy check of the original ammeter is to disconnect both leads going to the ammeter and check the resistance across the ammeter. If it is infinite then the wire inside the gage is probably open. I fixed one of these in the past by opening it up and replacing the open wire with a single strand from a multi strand wire. The key is getting a wire with similar gage and maintaining the same number of turns on both sides of the needle. You'll see what I mean if you open it up. Make sure you spray lacquer on the wire except for the ends that will be soldered. The reason for this is to prevent current flow from short circuiting the turns on the wire. Good luck.

Don

bmg · 03-27-2005, 01:17 AM

well i left it the way it was hooked up........ hard wired........when i tried with the new board it started smokin.......so i pulled the plug and just taped that part of the circuit off and all is well now............its a stock gage but hey it works hard wired so i will leave it thanks for the input later all

03-25-2005, 05:53 PM	#1
bmg Registered User Join Date: Nov 2001 Location: Indianapolis, IN USA Posts: 157	AMP Gague woes I am about to replece my circuit board on the dash and have a question about the amp gage. It is hard wired to that alternator can i just not hook that part of the circuit board up or will that screw the whole board from working properly. if not then just don't hook the hard wires back up on the back of the gage and tape em off.. just not sure what i need to do to make it work properly with the least chance of making a huge mess.

03-25-2005, 08:44 PM	#2
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Since the factory ammeter runs off of very low power both wires are hooked to the main feed wire that goes to the cab. The ammeter reads the resistance power in the wire and is not connected to the alternator. It reads depending on which way power is flowing in the main feed. If you were to run alternator amperage through a stock ammeter it will fry the meter. The stock ammeter is protected by two small 4 amp fuses. If you disconnect the two connections or wires on the ammeter it will have no effect on the running, charging or the way other gauges work. Jim Last edited by JimKshortstep4x4; 03-26-2005 at 07:14 AM. Reason: Corrected spelling

03-26-2005, 12:22 AM	#3
Robert1970C20rstbukt Registered User Join Date: Jun 2004 Location: Beeville, Texas Posts: 1,943	By any chance are these wires y'all are talking about dark purple? There's an aftermarket amp gauge bolted to the bottom of the dash in my truck and it has two 10 gauge dark purple wires hooked to it. When I take off either one all the power inside the cab goes dead. Are these supposed to be hooked up to the stock ammeter in the dash or something? Not tryin to hijack the thread but I've been wondering about this for a long time. __________________ RJD 1984 Chevrolet C30 welding truck 454/SM465 1977 GMC C15 pickup 350/TH350 1970 Chevrolet C20 pickup 350/TH400 1970 Chevrolet K20 Suburban 454/TH350 1969 GMC 8500 478M V6/5 spd winch truck

03-26-2005, 01:37 PM	#5
Robert1970C20rstbukt Registered User Join Date: Jun 2004 Location: Beeville, Texas Posts: 1,943	Nope, when I pull either wire everything shuts down. Do those wires hook to the back of the factory amp gauge in the dash, even though the printed circuit is already there? I checked all the wiring and replaced both fuses in the harness and the factory one never worked. __________________ RJD 1984 Chevrolet C30 welding truck 454/SM465 1977 GMC C15 pickup 350/TH350 1970 Chevrolet C20 pickup 350/TH400 1970 Chevrolet K20 Suburban 454/TH350 1969 GMC 8500 478M V6/5 spd winch truck

03-26-2005, 01:42 PM	#6
Bob Moore Registered User Join Date: Feb 2004 Location: Tacoma WA Posts: 1,365	Robert - The only 10 ga. purple wires I am familiar with in the cab are normally attached to the neutral safety switch. Do you have an automatic or has someone switched harnesses? Are there wires to your N/S? __________________ 67 C-20 LWB, tilt, speed alert, vac, 454, T400 67 C-10 SWB, factory air with more to follow

03-26-2005, 03:04 PM	#7
bmg Registered User Join Date: Nov 2001 Location: Indianapolis, IN USA Posts: 157	mine is hard wired from the back of the gage to: red wire directly to the alternator and blue wire goes to the voltage regulator that is bybassed.... so i am wondering if i don't hook these wires back up will the system still charge like its suppose to ............off the dash circuit board

03-26-2005, 05:09 PM	#8
Robert1970C20rstbukt Registered User Join Date: Jun 2004 Location: Beeville, Texas Posts: 1,943	Bob- My truck was always an auto truck. I have checked the Neutral SS wires and they are uncut, all the way to the plug. I did have to unplug and jump the NSS because it's screwed up and it would shut the engine off with the tranny in any gear. The ones hooked to the aftermarket ammeter run through the firewall into the factory alternator/charging harness. They look dark purple but they could be black, it's really hard to tell what color they are while standing on your head. If someone could post a wiring diagram it might help, I don't have any saved on my computer. __________________ RJD 1984 Chevrolet C30 welding truck 454/SM465 1977 GMC C15 pickup 350/TH350 1970 Chevrolet C20 pickup 350/TH400 1970 Chevrolet K20 Suburban 454/TH350 1969 GMC 8500 478M V6/5 spd winch truck

03-26-2005, 05:25 PM	#9
Old Dave Is a bullfrog waterproof? Join Date: Nov 2000 Location: OLATHE, KANSAS Posts: 1,130	Found this link on an old post:http://www.geocities.com/chevroletc1070/wiringdias.html __________________ "It is better to remain silent and be thought a fool, than to open one's mouth and remove all doubt." Ben Franklin __________________ 1970 Chevy shortbed 2002 Harley Custom Chopper (Long sucker) 1998 K2500 5.7L 5-speed Longbed 1st two are My son's toys...they just live in my garage! 1997 GMC K1500 Suburban 1993 S-10 Blazer 4D (youngest son's daily driver) 2000 Dodge Ram 4WD Ext. Cab (5.9L) Wife is a late year 1951

03-26-2005, 07:17 PM	#10
john member #16 Join Date: Dec 1999 Location: Yuba City Ca. Posts: 3,618	Robert here are the factory wires. They are 18 ga. This guage will not handle any load. What you have is aftermarket wired so all your power runs through it. So to answer your question do not hook up to factory ga. or it will go poof. John Attached Images __________________ john http://67-72chevytrucks.com/vboard/showgroups.php board vendors http://www.flickr.com/photos/1745471...7602865984234/

03-26-2005, 07:49 PM	#11
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	BMG, I am assuming that you have an after market gauge which is wired very different from stock. The stock gauge picks up current from the wire resistance and can only be used for this kind of hook up. As someone said if you hook it up direct it will go "poof". What you probably have is an aftermarket gauge that is connected to the alternator in such a way that all current flows through the gauge. Depending on how it is wired it could shut off everything. I would recommend that you check it carefully. Since the total current is flowing through the gauge it must be designed to take the full current or the gauge will blow. I shy away from full amperage gauges because of the potential shorts. That is a lot of power that flows into your cab and back out again. Jim

03-27-2005, 12:16 AM	#12
Robert1970C20rstbukt Registered User Join Date: Jun 2004 Location: Beeville, Texas Posts: 1,943	John thanks for posting the pic, even though I forgot I have both of the '70 service and overhaul manuals with the diagrams in 'em. I traced the black white striped wire and i'm getting power through it, but the ammeter just sits there when I turn the key on and start the truck. Does anybody know an easy way to check the original ammeter to see if it is still good? Hey bmg again i'm sorry I wasn't trying to hijack the thread, I just read it and I started thinking wtf is wrong with the one in my truck. __________________ RJD 1984 Chevrolet C30 welding truck 454/SM465 1977 GMC C15 pickup 350/TH350 1970 Chevrolet C20 pickup 350/TH400 1970 Chevrolet K20 Suburban 454/TH350 1969 GMC 8500 478M V6/5 spd winch truck

03-27-2005, 12:38 AM	#13
ddsmith Glowing since 1978 Join Date: Mar 2001 Location: Lusby,MD,USA Posts: 532	An easy check of the original ammeter is to disconnect both leads going to the ammeter and check the resistance across the ammeter. If it is infinite then the wire inside the gage is probably open. I fixed one of these in the past by opening it up and replacing the open wire with a single strand from a multi strand wire. The key is getting a wire with similar gage and maintaining the same number of turns on both sides of the needle. You'll see what I mean if you open it up. Make sure you spray lacquer on the wire except for the ends that will be soldered. The reason for this is to prevent current flow from short circuiting the turns on the wire. Good luck. Don __________________ 66 Chevy C30 Stakebody Dump, PS,PB, 327cu in 71 Corvette Coupe 454 4 speed 69 Chevy C20 Custom Camper

03-27-2005, 01:17 AM	#14
bmg Registered User Join Date: Nov 2001 Location: Indianapolis, IN USA Posts: 157	well i left it the way it was hooked up........ hard wired........when i tried with the new board it started smokin.......so i pulled the plug and just taped that part of the circuit off and all is well now............its a stock gage but hey it works hard wired so i will leave it thanks for the input later all



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