1970 Beetle idiot light dim...

[Volky]

Good night to all,

I have a 1970 VW Beetle which I recently made it turbo. But even before the turbo project the car's idiot light is dim at night when I go for long trips and I turn off the car it won't start. The battery is ok and the alternator is new.

I was going to Google this issue when I had the chance but since I'm in STF I decided to post the issue.

Thanks.

[Marc]

Does the no-crank condition only occur when the engine/trans are warm? In other words, after it sits for a while does it then start? Such a "hot-soak" problem can be due to a worn starter bushing, or a borderline solenoid that's not receiving enough current to pull in (adding a "booster" relay is an expedient fix for that).

As for the warning light glowing, that may be related (perhaps a poor groundstrap connection?) or it might be a totally different issue. The light has no brains and can't differentiate the direction of current flow through it - so even when the alternator's working just fine, it can glow if there's sufficient voltage drop in the current path through the main harness to the headlight switch to the fusepanel to the ignition switch to the "hot" side of the bulb so that the higher voltage on the wire from the alternator makes it light. When the headlights are on there's more current drawn through the harness, causing a voltage drop to the downstream components...the symptom will be exacerbated if you have higher-output headlights, if that's the case running a dedicated 10GA supply wire from the battery to a headlight relay will cure it.

Do you have a voltmeter so you can check the voltage at various points along the path to the ignition switch when the headlights are on? Any drop of more than about 0.2v between one connection and the next warrants attention.

[Volky]

Hi Marc,

Does the no-crank condition only occur when the engine/trans are warm? In other words, after it sits for a while does it then start?

Yes, no-crank when hot. I go back to the car in a while and it starts quickly.

As for the starter, I'll sneak a peak at it. It's been there since I've known my wife 2001. Also, she bought the car in 1994 and she said she never changed it so, that could be it.

My ground strap is at the tranny base which is like zinc plated to a bolt at the starter.

I have a multimeter, I will check the cables.

Thanks,

[Marc]

Until you get this fixed, when possible open the hood when you shut down so the heat will get out sooner. Check that the battery ground cable also has a tight/clean connection to the pan, and of course the connections at the solenoid too.
If the starter bushing's worn, another symptom will be occasional slow, laboring cranking. If you decide to get another one, consider getting an AutoStick/Automatic starter. They're self-supporting and don't require a bushing. Last one I bought was a rebuilt at AutoZone (around $50) and it's been working like a champ.

[Ol'fogasaurus]

Also check if you still have braided/woven cable that comes off the chassis/shock mount area. Those... braided things..., even in non-VW cars have been known to be a pain in the sit-down area; I ran into problems with them in the older Fords and Chevs going back ~ to the WWII days (I forget when they started them but they do break down as the individual wires can fracture; usually, but not necessarily, by the solid ends of the cable.

I'd also get a charge reading at the battery with the engine running and warm.

How old is the battery too. If it is sulfated, tired or has bad connections this should be looked in to; brightly polished posts is good to have .

[helowrench]

I usually run a separate ground strap from the fuel pump rear stud over to the body somewhere in the engine compartment. cheap insurance.

You can (stone age troubleshooting here) turn the headlights on, and watch them as someone else tries to start the car.
if the headlights do not dim, it is either a connection problem such as a ground strap, or positive cable, or solenoid problem. (faulty circuit either way). then connect one lead of the jumper cables from an exposed point on the engine directly to the car body to see if it changes (eliminates ground braid) then try from engine block to battery( eliminates negative battery cable)
if the headlights dim a lot, then it is either a bad battery or the starter motor itself.

If neither of those changes it, then it is a trigger wire problem.
unplug the small wire under the back seat (goes to solenoid) and jumper it to the battery positive.
MAKE SURE THE CAR IS OUT OF GEAR.

[Volky]

Thanks to all,

I will start this on the weekend.

[Marc]

I usually run a separate ground strap from the fuel pump rear stud over to the body somewhere in the engine compartment. cheap insurance..

Brings to mind some problems I've seen on other cars. Fiats typically ran a small braided ground wire to the alternator, which would've been fine had they not enclosed it in the same harness as the other wires. First time the main ground strap fails, that little lead ends up trying to handle the starter current draw and goes up in smoke (if you're lucky, it only ruins the harness and doesn't result in a fire).
Rabbits had a little tab on the negative battery cable that was bolted to the body; if the primary ground strap to the engine failed, when you turned the key to the crank position the starter draw would seek other paths, like through the oil pressure switch and the dashboard (!)

The particular addition you've mentioned shouldn't cause any such problems, but it seemed like a good place to mention that when you make modifications to the wiring always think through the worst-case scenario

[Ol'fogasaurus]

On most older cars it is the ground or it's grounding that so often is a major problem. I try to stay away from putting anything electrical, more than what is already there (stock), on or near where fuel, especially with a disconnect or two like a fuel pump has is already in place (sorry about the fractured sentence but I was trying to cover a lot of things as fast as I could... potential sparks and fuel are strange bedfellows).

On my buggy I run a/the ground strap directly to a bolt on the bell housing preferable to one of the starter bolts. On my buggy I also have a ground shut-off as a back up/safety device to stop potential arcing (in case I forget to disconnect the ground cable first) or detour theft but on a street car, especially if it is a restored Bug or a stocker where stock looks is important, I may or not do the same thing or hide it well but at the same time, make it easy to get at.

Lee

While the ground probably shouldn't arc especially in the case of removing it then accidentally re-grounding it as you move the cable away from where is was grounded. I have seen it do so especially with all the electronics now days with some of components holding a charge.

[Volky]

Good day,

It's been a while, I thought I had sorted out the issue since my last post. Everything was good (no dim light) until about two weeks ago. The car starts with power and runs on about 13.8 or less volts. I get to my destination and it has 12 volts or less but starts with power. The light is red but not as brifht as if you put the key on the ON position when cold.

It runs at 12v's or less with or without the lights on.

B4 buying a new alternator I was thinking of replacing the thick RED cable that goes from front to back. Also, maybe change my light switch, too.

Anything I should look for?

Thanks,

[Ol'fogasaurus]

If I remember my auto electronics correctly: the work is done by the ground side. The ground wire should be the same size as the wire it is supporting. Just for giggles, if you can run a battery cable, larger than the stock gauge wire (voltage drop) directly from the battery ground to the engine, and see if this make any difference.

I have also seen ignition switches create problems too.

[Dale M.]

Ground conductor (cable) has to have same current carrying capacity as "battery" cable.... All auto circuits are essentially a loop from negative side of battery to positive side of battery with radios and lights and what knots in middle of loop.... Check ground cable at battery and at chassis connection (clean bright shinny protected with dielectric grease) and also ground strap at front mount on transaxle to chassis...

I really suspect alternator... You should see 14 volts at B+ and D+ terminal (both terminal should show same voltage) on alternator with engine just a above idle speed

Dale

[Reggie]

Hi,
I have a 36V Alternator I intend to use for alternative energy, my only problem is the Idiot light, can I go for a 36V dc bulb as the idiot light, or what kind of resistor can I use in place of the idiot light bulb? Looking forward to your kind response.

[Dale M.]

Need to know more about alternator, is it 2 wire?... With D+and B+... First impression is separate lamp circuit with 36v bulb...

Dale

[Reggie]

Yes, the alternator has a D+ and B+ wires.