Electrical puzzler...

DorianL

DorianL

solid fixture here in the forum
Staff member
Here we go...

Hm, something wrong with my electrical system on my air-cooled.

This weekend the idiot light started to glow faintly, so I tightened the fan belt (which was quite slack). I thought that had fixed the problem. I measured the voltage with engine running

13.87v lights off
13.23v lights on

Yesterday... that idiot light came only after driving all the way to work. Same coming back - it only started glowing half way home. When I got home, the idiot light had gone out again. I checked the voltage with then engine running: 12.4v I should have checked if the alternator was hot but forgot to.

Hmmm, I want to be methodical tracking down my problem... This car has had some electrical issues in the past. Headlights are supposed to flash when the car locks and unlocks... that seemed to blow the fuse of the control unit every time.

I am thinking of investing in one of those clamp Ammeters. Any thoughts on that?
 
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I am going to start by exploring around the alt for loose wires and the like.

That seems like the obvious first step.
 
the first thing ID check is the battery cable connections and grounds to the frame and the alternator output at the alternator , then the ohms resisitance in major battery cable connections
ampm1.jpg
image_12926.jpg






THINK LOGICALLY ,ISOLATE AND TEST,NEVER ASSUME!
PULL THE TROUBLE CODES AND USE THE SHOP MANUAL AS A GUIDE,
YOU may be amazed at the number of times a bad sensor or loose wire, bad ground or blown fuse is the problems cause.
I've seen guys rush out and spend hundreds of dollars on parts,too fix a problem, take a great amount of effort to tear apart the dash or other area and once the new parts installed it still won't work, so forced to do further research at that point they only then find a blown fuse or corroded electrical connection.(that was the true initial cause)


viewtopic.php?f=50&t=3110&p=12074&hilit=multi+meter#p12074
image_6238.jpg

http://www.harborfreight.com/5-in-1-dig ... 98674.html
some related threads that should help
http://garage.grumpysperformance.co...ing-down-an-electrical-drain.8493/#post-37179

http://garage.grumpysperformance.co...tting-out-low-voltage.12221/page-2#post-59599

http://garage.grumpysperformance.com/index.php?threads/testing-an-alternator.3222/#post-46703

http://garage.grumpysperformance.co...lternators-and-oil-all-here.12628/#post-64603

http://garage.grumpysperformance.com/index.php?threads/how-altenators-work.355/#post-62266

http://garage.grumpysperformance.co...uys-don-t-look-at-the-clues.11176/#post-50125

http://garage.grumpysperformance.com/index.php?threads/suspicious-voltage-drop.10718/#post-46927
 
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(MF!!!! Would you believe that I bought the only clamp Ammeter they had got home and realized it only did AC :mad::mad::mad:)
 
Watching video and going through the links.

How much draw should head lights have? The turn signals also have lights in them that turn on when the headlight are on.
 
TYPICAL ACCESSORY CURRENT DRAW (AMPS)
Lights
Headlights (high beam)40
Headlights (low beam) 10-22
Tail Lights 8
Safety
Emergency brake light 4
Emergency flasher 15
Turn signals 10-15
Windshield wipers 6-20
Horn 15
Brake lights 15-20
Running lights 8
Ignition
Winter starting 225-500
Summer starting 100-400
Approx. Avg. 300
Courtesy
Cigarette lighter 15-20
Interior lights 10-15
Instrument panel lights 4
Entertainment
Radio 10
Stereo Tape 10
Electric antenna 20
Comfort
Air conditioner 10
Heater 20-30
Defroster 15-30
Electric seat 20
Electric windows 20-30
TYPICAL ACCESSORY CURRENT DRAW (AMPS)
510SH.jpg

Typical Current Loads for Automotive Systems, Lighting and Accessories:
Engine Idling (no lights or accessories on) - 35 to 50 amps. This will vary depending on the number of cylinders (more cylinders draw more power for the fuel injectors and coils), the type of fuel injectors (some draw higher amp loads than others), the type of ignition system (single coil or multi-coil), the amp draw of the PCM, and the fuel pump (the amp draw will be higher with higher pressure systems).

Engine Off (nothing on) - 40 to 50 milliamps (power drain by modules in sleep mode, antitheft system and keyless entry)

Ignition Coil (single oil-filled coil older vehicle) - 3 to 4 amps.

Ignition Coil (single DIS coil newer vehicle) - 5 to 6 amps.

Ignition Coil (coil-on-plug) - 6 amps per coil.

Ignition System (primary circuit) - 6 to 20 amps.

Fuel Injectors - 4 to 6 amps peak, 1 amp hold

Electric Fuel Pump (depends on pressure and flow) - 4 to 12 amps

Electric Cooling Fan (depends on size) - 6 to 30 amps

Headlights (halogen low beam) - 8 to 9 amps per pair

Headlights (halogen high beam) - 9 to 10 amps per pair

Headlights (halogen high and low beams combined) - 17 to 19 amps

Headlights (High Energy Discharge) - 12 to 14 amps during initial start, 7 to 8 amps once bulbs are hot

Headlights (LED) - 0.6 to 1 amps per bulb

Small bulbs (incandescent) - 0.3 to 0.4 amps per bulb

Small bulbs (LED) - 0.04 to 0.06 amps per bulb

Starter Motor - 200 to 350 amps

500 Watt Sound System - 42 amps

Electric Rear Window Defroster - 10 to 20 amps

Windshield wipers - 2 to 10 amps depending on load

Heated Seats - 3 to 4 amps per seat

Power Windows - 3 amps

Electric Power Steering - 2 to 40 amps depending on load

Air Conditioner Compressor Clutch - 2.5 to 5 amps

Heater A/C blower motor (depends on load, size and speed setting) - 2 to 30 amps
 
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Right. I took the car for a drive (daylight with no headlights on) and there were no problems. I get 14v at idle. Briefly putting headlights on I get half a volt drop at the battery. That seems excessive. No?

The at rest draw is around 30mA. My guess is that's about right for the keyless entry that's constantly scanning for the RFID fob. I'll verify.

Brrr. Getting nut-freezing cold out there in my driveway.

More tomorrow.

I really suspect my headlights might be drawing a lot.

I think the alt is rated at 50 ~ 60 Amps
 
probably
good catch,
high beams can and usually do work with and in addition to low beams
I corrected the typo
I added a second chart

btw IVE swapped to a 200 amp alternator in my corvette and it noticeably improves ignition spark and fan speeds
I learned decades ago to swap to a 140 amp-200 amp alternator,
as the stock 75-105 amp alternators on muscle cars and earlier corvettes are marginal at best/
if you shop carefully they can usually be found locally at some alternator re-builders for under $150
both my corvettes have 200 amp versions purchased NEW for under $250
while that may be over-kill to some I find the electric fans on the corvette and ignition and head lights work noticeably better





https://www.dbelectrical.com/alternators/automotive/chevrolet/corvette/5-7-liter/

http://www.ecklerscorvette.com/corvette-alternator-140-amp-chrome-power-master-1969-1982.html
 
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Interesting.

I turned headlights on. 1500 rpm. Voltage drop test negative to negative and red probe to Alt case. I got 0.36 Volts. Hmmmmmm from what I understand, it should be WAY lower than that.
 
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Yes. Once the vette is here, 200 Amps seems like a good idea.

On this air-cooled fellow, I got the highest best alt available here: 55 Amps.
 
that reading usually indicates a loose electrical ground or internal short in wiring
 
isolate and test each ohms resistance test,
individual battery cable and engine to frame ground then look carefully at the electrical connectors,
most of the time its a corrosion issue between connectors and pins ,
or loose battery cable connections
I had a head light wire that was being compressed between a fender and grill that the previous owner replaced on my 1965 PONTIAC LeMans that drove be a bit nuts until I found it, but simply narrowing its potential location by testing led me too it ans taught me a good deal about how to use a multi-meter back in about 1968

http://garage.grumpysperformance.com/index.php?threads/voltage-is-wrong-after-alternator-swap.13580/

http://garage.grumpysperformance.co...-intermittent-ignition-miss.13253/#post-69106
 
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Before you get too deep into it, how old is that alternator? My guess is the brushes are about done.
If so, if you continue to run it this way, you will burn the rotor connections where the brushes ride.
Pull the alternator and have it tested at your local auto parts store.
 
Yay. It's the next morning. I can hint more for that electrical issue.

The alternator is less than three years old

As for corrosion, it's a KG but a completely new GM harness in there. Corrosion is less likely than something pinching or unhooked
 
Ok. Well that was a fuss. I found a clamp ammeter. With the headlights (low beam), side markers and tail lights on, the total draw was... 5 Amps. Is it just me, or is that remarkably low and a sign of poor grounding?

I krept under the car to inspect the ground strap. It looks quite dirty. What do you think.

I'm increasingly leaning toward bad ground.

If the ground was excellent, should the lights be drawing more?

IMG_4672.JPG
 
Well that was interesting, the groundstrap fell apart in my hands. Cleaned everything up and installed a new one. The headlights, side markers and tails lights went from 5 Amps to 15 and 16 at high beam.

Still seems to be a voltage drop. Further exploring necessary

PS does this mea my headlights will be brighter? o_O
 
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Tomorrow I'm going to go through the battery cables. I would suspect that the draw would be much greater if the lights had a short somewhere, no?
 
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