Wierd electrical issue
November 27th, 2010, 08:06 PM
#1
Wierd electrical issue
So, I'm trying to diagnose why the dome light wouldn't come on, so I pull the gauge bezel and bits to check for dead bulbs. I turn the ignition on, and notice that um...when I turn on the headlights, the fuel gauge drops below E to the BRAKE indicator. As I turn the dimmer on the headlight switch, the gauge moves. Is this an indicator of a problem ina particular point in the system, or just that I have a short somewhere arbitrary?
Another problem I've noticed electrically is slow flashers when at idle, and they speed up to normal as I accelerate. When I put the hazard lights on, they flash really fast, and unevenly.
Pointers, anyone? I've been lucky enough in my other cars to have no real electical problems, and now I have to fix this one.
The car is a 1972 Cutlass S 350/2bbl.
Another problem I've noticed electrically is slow flashers when at idle, and they speed up to normal as I accelerate. When I put the hazard lights on, they flash really fast, and unevenly.
Pointers, anyone? I've been lucky enough in my other cars to have no real electical problems, and now I have to fix this one.
The car is a 1972 Cutlass S 350/2bbl.
Last edited by ChefDeadpool; November 27th, 2010 at 08:11 PM.
November 28th, 2010, 01:42 AM
#2
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Join Date: Jun 2010
Location: Lebanon, Ohio
Posts: 226
Chef,
It's 4:00 AM and I'm getting ready to go to the Indy Swap Meet, but I'll take a second and give you a few hints.
Whenever devices start interacting I get suspicious of the grounds in the system. I would start by finding them and cleaning up the connections. The biggies are the battery to the engine block and the block to the body, and ultimately the body to the frame. By design, each device has a ground, somewhere, that lets current flow back to the negative terminal of the battery.
When these grounds get corroded, the current sometimes flows back through other devices. Thus, the interaction. I had an '80 Rabbit VW (insert your own curse words here) that lost it's frame ground. Current that usually flowed back thru the frame went back through the speedometer return spring. Since the spring could only handle a little current, it fried and the speedo pegged permanently (even with the car off)! This was a documented failure mode in the aftermarket repair manual.
On A-bodies, the dome light switches either ground in the door jambs to the body through the threads to the jamb (a 1-wire switch), or they have a second wire for a ground (a 2-wire switch).
The instrument cluster will also have a ground. I don't know if it's a wire in the harness, or a separate wire on an Olds. You can add an extra ground wire from the case to the dash frame. Tail lights will sometimes have a pigtail that wires to the body. In general, try troubleshooting by adding grounds to light housings, engine blocks, alternator cases, etc., and see if things improve.
You may have multiple problems. The thing with the flashers speeding up tells me the voltage goes up when you rev the engine. Use a voltmeter to measure the voltage at the battery, then at the alternator output, then at a tail light while your able assistant revs the engine. I'm betting the alternator stays constant but the ones elsewhere increase with engine speed.
The first step is a lot like trying to figure out an engine miss. You need to first "tune up" your electrical system (e.g., clean up the grounds) just like you do with your ignition system.
Gotta go for now. Hope this gets you started...
It's 4:00 AM and I'm getting ready to go to the Indy Swap Meet, but I'll take a second and give you a few hints.
Whenever devices start interacting I get suspicious of the grounds in the system. I would start by finding them and cleaning up the connections. The biggies are the battery to the engine block and the block to the body, and ultimately the body to the frame. By design, each device has a ground, somewhere, that lets current flow back to the negative terminal of the battery.
When these grounds get corroded, the current sometimes flows back through other devices. Thus, the interaction. I had an '80 Rabbit VW (insert your own curse words here) that lost it's frame ground. Current that usually flowed back thru the frame went back through the speedometer return spring. Since the spring could only handle a little current, it fried and the speedo pegged permanently (even with the car off)! This was a documented failure mode in the aftermarket repair manual.
On A-bodies, the dome light switches either ground in the door jambs to the body through the threads to the jamb (a 1-wire switch), or they have a second wire for a ground (a 2-wire switch).
The instrument cluster will also have a ground. I don't know if it's a wire in the harness, or a separate wire on an Olds. You can add an extra ground wire from the case to the dash frame. Tail lights will sometimes have a pigtail that wires to the body. In general, try troubleshooting by adding grounds to light housings, engine blocks, alternator cases, etc., and see if things improve.
You may have multiple problems. The thing with the flashers speeding up tells me the voltage goes up when you rev the engine. Use a voltmeter to measure the voltage at the battery, then at the alternator output, then at a tail light while your able assistant revs the engine. I'm betting the alternator stays constant but the ones elsewhere increase with engine speed.
The first step is a lot like trying to figure out an engine miss. You need to first "tune up" your electrical system (e.g., clean up the grounds) just like you do with your ignition system.
Gotta go for now. Hope this gets you started...
November 28th, 2010, 06:31 AM
#3
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Join Date: Feb 2008
Location: Plano, TX
Posts: 11,798
Bob had some good advice to start with and I bet there are multiple issues. The 72 Olds cluster uses a ground wire in the harness, but I think also has a metal contcat where a mounting screw goes. Time to pull the cluster and check the pins on the back that go into the connector. Sometimes these break loose, needing to be resoldered.
Do use a voltmeter to check at battery and alt and inside car at fusebox. This can tell us a lot of things. Check the grounds, too, and report back your findings.
Do use a voltmeter to check at battery and alt and inside car at fusebox. This can tell us a lot of things. Check the grounds, too, and report back your findings.
November 28th, 2010, 06:33 AM
#4
Chef,
It's 4:00 AM and I'm getting ready to go to the Indy Swap Meet, but I'll take a second and give you a few hints.
Whenever devices start interacting I get suspicious of the grounds in the system. I would start by finding them and cleaning up the connections. The biggies are the battery to the engine block and the block to the body, and ultimately the body to the frame. By design, each device has a ground, somewhere, that lets current flow back to the negative terminal of the battery.
When these grounds get corroded, the current sometimes flows back through other devices. Thus, the interaction. I had an '80 Rabbit VW (insert your own curse words here) that lost it's frame ground. Current that usually flowed back thru the frame went back through the speedometer return spring. Since the spring could only handle a little current, it fried and the speedo pegged permanently (even with the car off)! This was a documented failure mode in the aftermarket repair manual.
On A-bodies, the dome light switches either ground in the door jambs to the body through the threads to the jamb (a 1-wire switch), or they have a second wire for a ground (a 2-wire switch).
The instrument cluster will also have a ground. I don't know if it's a wire in the harness, or a separate wire on an Olds. You can add an extra ground wire from the case to the dash frame. Tail lights will sometimes have a pigtail that wires to the body. In general, try troubleshooting by adding grounds to light housings, engine blocks, alternator cases, etc., and see if things improve.
You may have multiple problems. The thing with the flashers speeding up tells me the voltage goes up when you rev the engine. Use a voltmeter to measure the voltage at the battery, then at the alternator output, then at a tail light while your able assistant revs the engine. I'm betting the alternator stays constant but the ones elsewhere increase with engine speed.
The first step is a lot like trying to figure out an engine miss. You need to first "tune up" your electrical system (e.g., clean up the grounds) just like you do with your ignition system.
Gotta go for now. Hope this gets you started...
It's 4:00 AM and I'm getting ready to go to the Indy Swap Meet, but I'll take a second and give you a few hints.
Whenever devices start interacting I get suspicious of the grounds in the system. I would start by finding them and cleaning up the connections. The biggies are the battery to the engine block and the block to the body, and ultimately the body to the frame. By design, each device has a ground, somewhere, that lets current flow back to the negative terminal of the battery.
When these grounds get corroded, the current sometimes flows back through other devices. Thus, the interaction. I had an '80 Rabbit VW (insert your own curse words here) that lost it's frame ground. Current that usually flowed back thru the frame went back through the speedometer return spring. Since the spring could only handle a little current, it fried and the speedo pegged permanently (even with the car off)! This was a documented failure mode in the aftermarket repair manual.
On A-bodies, the dome light switches either ground in the door jambs to the body through the threads to the jamb (a 1-wire switch), or they have a second wire for a ground (a 2-wire switch).
The instrument cluster will also have a ground. I don't know if it's a wire in the harness, or a separate wire on an Olds. You can add an extra ground wire from the case to the dash frame. Tail lights will sometimes have a pigtail that wires to the body. In general, try troubleshooting by adding grounds to light housings, engine blocks, alternator cases, etc., and see if things improve.
You may have multiple problems. The thing with the flashers speeding up tells me the voltage goes up when you rev the engine. Use a voltmeter to measure the voltage at the battery, then at the alternator output, then at a tail light while your able assistant revs the engine. I'm betting the alternator stays constant but the ones elsewhere increase with engine speed.
The first step is a lot like trying to figure out an engine miss. You need to first "tune up" your electrical system (e.g., clean up the grounds) just like you do with your ignition system.
Gotta go for now. Hope this gets you started...
November 29th, 2010, 07:26 AM
#5
I'll get back with you all on this when the factory service manual comes in the mail - I'm not familiar with where everything is on this car yet, so I'm going to leave it as running for the time being. Everything still *mostly* works, and I need to be able to get to my job/school.
December 9th, 2010, 02:25 PM
#6
Well, without the manual, I managed to figure out that my stereo is wired completely wrong - the ground isn't even connected, and the orange wire from the stereo (12v constant, supposed to be run to the battery) is connected to an unknown orange wire in the car. Where do the wires come in through the firewall to the passenger compartment? I'd like to eliminate this issue first, as I noticed sometimes the stereo works, sometimes the fuel gauge lights work.
December 9th, 2010, 03:12 PM
#9
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Join Date: May 2008
Location: Dallas
Posts: 651
and the orange wire from the stereo (12v constant, supposed to be run to the battery) is connected to an unknown orange wire in the car. Where do the wires come in through the firewall to the passenger compartment? I'd like to eliminate this issue first, as I noticed sometimes the stereo works, sometimes the fuel gauge lights work.
Yellow and Gray (2 wires) from fuse box should be going to your radio.
The Gray wire also feeds some of the other lights in the dash, ex: heater, ashtray, clock, and light switched light.
PM if you have any questions.
Photos never hurt either.
Last edited by hamm36; December 9th, 2010 at 03:14 PM.
December 9th, 2010, 03:26 PM
#10
WHAT. My dome light doesn't work, neither do any of those things you list. THe heater has a light? No wonder I couldn't see the controls!
And the orange wire is cut and patched into the stereo.
I'm going to fix this tonight...
What sort of idiot wires things this way?
And the orange wire is cut and patched into the stereo.
I'm going to fix this tonight...
What sort of idiot wires things this way?
December 9th, 2010, 04:23 PM
#11
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Join Date: Sep 2006
Location: Richmond, TX
Posts: 190
If I remember right, the orange wire is always hot while the gray is hot with the headlights/parking-lights turned on (which is how numerous lights in the dash come on with the headlights switch). The gray wire is also dimmed via the interior light dimmer in the headlight switch.
December 9th, 2010, 06:01 PM
#12
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Join Date: Jun 2010
Location: Lebanon, Ohio
Posts: 226
If I remember right, the orange wire is always hot while the gray is hot with the headlights/parking-lights turned on (which is how numerous lights in the dash come on with the headlights switch). The gray wire is also dimmed via the interior light dimmer in the headlight switch.
December 9th, 2010, 06:11 PM
#13
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Join Date: Jun 2010
Location: Lebanon, Ohio
Posts: 226
Well, without the manual, I managed to figure out that my stereo is wired completely wrong - the ground isn't even connected, and the orange wire from the stereo (12v constant, supposed to be run to the battery) is connected to an unknown orange wire in the car. Where do the wires come in through the firewall to the passenger compartment? I'd like to eliminate this issue first, as I noticed sometimes the stereo works, sometimes the fuel gauge lights work.
December 9th, 2010, 08:38 PM
#14
If I were you I wouldn't worry too much about the stereo. You have a ground problem. The stereo is supposed to ground through the case to the dash. If it's hot side is connected to the orange wire it will play even when the ignition is off (no big deal). It sounds to me like the dash is sometimes grounded, sometimes not. As a test, run a temporary long wire from the negative battery terminal directly to the metal dash frame and see if all of your problems go away.
I'm going to pull the stereo, attach the wires back to where they belong, and then I'll start running grounds to see if I can straighten this out if I need to.
Meanwhile, where is the engine block to frame ground strap on this car? On my one F-Body I checked for it, it was on the back of the engine attached to the firewall, but that probably wasn't factory. I didn't see one like that on the Cutlass.
December 10th, 2010, 04:54 AM
#15
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Location: Lebanon, Ohio
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Ehh, you wold be worried about the stereo if you saw what the previous owner did to the orange wire besides hook it to the stereo. There was some kind of hackjob to put a cigarette lighter on the floor(for a cellphone I assume). I detached the orange wire, and it looks like there's an issue with exactly where it was attached to before it was attached to the stereo. It's really scary, electrical tape attaching everything, etc...
December 10th, 2010, 05:11 AM
#16
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Location: Plano, TX
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DO get all that hooked up again right - use solder joints an heat shrink tubing to make splices.
That big orange also fed the courtesy lights, clock, and lighter.
Gray was for dimmable dash lights as said already.
A factory radio will use that for the dial light; an aftermarket radio will most likely not use the gray.
You already answered that.
Down here we call them igmos...
December 10th, 2010, 05:38 AM
#17
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Location: Lebanon, Ohio
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On page 384 of the '69 Assembly Manual it looks like there's a pigtail coming off the negative battery cable that goes to the frame, but the picture of it's not great, so I'm not sure. So I looked in the Fusick parts catalog #43C and, sure enough, they show a picture of at least one negative battery cable with a pigtail. If this pigtail is supposed to be there, and if your battery cable has been changed out for a generic one over the last 38 years, you may not have this frame-grounding wire. I would run a wire from somewhere on the block to the frame, or order the correct battery cable.
The majority of the wires to/from the passenger compartment go through the bulkhead connectors below the brake master cylinder.
December 10th, 2010, 12:42 PM
#18
Keep in mind that you had to have the mirrors and lamps package option to have the glove box light, trunk light, and heater / wiper control lights.
That big orange also fed the courtesy lights, clock, and lighter.
Gray was for dimmable dash lights as said already.
A factory radio will use that for the dial light; an aftermarket radio will most likely not use the gray.
That big orange also fed the courtesy lights, clock, and lighter.
Gray was for dimmable dash lights as said already.
A factory radio will use that for the dial light; an aftermarket radio will most likely not use the gray.
December 10th, 2010, 01:59 PM
#20
The electrical tape seems to be localized to the stereo area, and the cigarette lighter. Nothing much else was touched.
The PO seemed to also enjoy using it to cover underhood wires.
The PO seemed to also enjoy using it to cover underhood wires.
December 10th, 2010, 10:16 PM
#21
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Location: New Brunswick Canada
Posts: 330
I beleive the signal lights are suposed to flash alternately when the head lights on,when the front light is on the side light will flash off,when the side light is on the front light will flash off. I like to use butt connectors when repairing wires,the type without insulation on them and I use heat shrink
December 11th, 2010, 07:06 AM
#22
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Location: Plano, TX
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I believe so, but check the manual for your particular radio.
December 26th, 2010, 07:55 AM
#23
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Location: Dallas
Posts: 651
Chef, if it is butchered up as much as it appears in your thread? I would get a couple of new/used harness' and pull your old one. Out of the new/used harness' I would make one good one. No splicing, or any of that. Color matching the wires to the correct locations. Non-glue tape back together.
There are two separated harnesses under your dash, the main one, and the one that feeds the exceresey lights. Pull both. To do it right you need to pull the dash/plastic part.
This is how I redid mine.
There are two separated harnesses under your dash, the main one, and the one that feeds the exceresey lights. Pull both. To do it right you need to pull the dash/plastic part.
This is how I redid mine.
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