Suddenly No Juice--no lights.

LynnsABCs · 08:56 AM

304065 · 11-12-2003, 06:50 AM

Lynn,

Forget the ignition switch for the moment, the problem is more fundamental than that.

Download the wiring diagram from the Pelican main page

http://www.pelicanparts.com/911/911_Parts/Electrical/911_electrical_1971_Part-2.jpg

Get yourself a multimeter from Radio Shack, does not have to be an expensive digital one, if you don't already have one.

1. Battery. Are you CERTAIN it tested good? Was it tested with a loadmeter, the kind that looks like a miniature electric toaster with a heating element?

2. Where is this battery located? Have you converted to a single battery setup? If so, on which side? If you did, what happened to the crossover cable to the other side?

3. You cleaned the ground strap to the body, good. What was the condition of the strap, was it badly oxidized? Just curious as to the overall condition of the electrics.

4. So you jacked up the car, supported it securely with jackstands, and crawled under the starter, got grease all over your hands and with a flashlight were able to verify that a) the battery positive cable is attached firmly to the starter terminal and the nut is tight and b) the faston connector for the starter solenoid is securely fastened to the solenoid. And yet, you say, between ground and the battery positive terminal, you have no 12v.

That terminal should be hot all the time if your battery is good and the battery cable is unbroken from the trunk to the starter terminal. Hence the questions above.

What is confusing is that you had a good horn and a hazard switch. Looking at the diagram I can see why you suspected the ignition switch, these things bypass it. But the more fundamental question is, why don't you have voltage at the biggest wire in the car. Fix that and you're on the way to resolving everything.

Good luck!

304065 · 11-12-2003, 07:43 AM

Quote:

If I have voltage at the starter with the key switched on does that mean the electrical part of the ignition switch is bad or is something else going on?

When you turn the ignition switch to "Start" you close the circuit inside the switch. Current travels from the battery into the switch and down the yellow wire, through the two 14-pin connectors and into the engine wire harness, into the wire that threads through that square rubber grommet at the forward part of the engine compartment and into the solenoid through the faston connector we talked about.

The current energizes the magnet which pulls in the wiper and closes the circuit between the starter and the hot wire from the battery. The engine cranks.

So you see, you should measure battery voltage on the positive starter terminal regardless of the position of the ignition switch.

You put a screwdriver between the battery positive terminal and the tab connector for the solenoid. OK, assuming you have a good engine to chassis ground strap, all 800 CCA from the battery should have flowed at that point, energizing the solenoid, cranking the engine, scaring the living hell out of you and turning your screwdriver and the tab on the starter into molten metal. (!)

If that DIDN'T happen you still might not be getting battery voltage to the starter because of a short in the primary cable somewhere. But if you had a good battery and a shorted primary cable, you'd probably have symptoms elsewhere in the car, like a FIRE!

What voltage do you measure at the battery terminals?

SweetE · 11-12-2003, 11:14 AM

You might want to check your Alternator.
My 71E did the same thing - replaces the atl now is fine.

304065 · 11-12-2003, 01:09 PM

The alternator has nothing to do with the ignition circuit. Out of the ignition switch there's a red wire with black stripe that daisy-chains across the back of the gauges, and also goes to one terminal of the alternator warning light bulb. The other terminal is a blue wire that goes all the way back to the voltage regulator and then to the alternator, the famous D+/61 circuit, of which MUCH has been written lately.

A dead alternator will give you a dead battery, yes, but the car should start and run (for half an hour or so) off the battery alone.

No, assuming that your battery is good, what you have is a current distribution problem, caused by some wire or connection, somewhere, that is broken, disconnected, or oxidized! The only way to trace it is to start with a known good battery and work your way OUT until the problem is identified.

The electrical system of an early car isn't complicated, and the wiring diagram is easy to read (really!) It just takes patience and the willingness to trace each circuit with your fingertip on the diagram, to find out what is connected to what, and then to test things in the car.

Lynn, if you check for voltage at the starter positive terminal and you find it, then go down to the fuse block. The positive battery connector should have not only the large black wire coming off it, but three fat red wires. One goes aft to the BHKZ (CD) unit. One goes to terminal #1 on the upper fuse block. And the last one goes through that six-pin cannon plug you were talking about, to the . . . ignition switch.

If you measure +12v at the battery, then you should be getting +12v at either side of fuse #1 on the upper fuse block. Then, are you getting +12v in ANY pin of that cannon plug, measured from underneath the dash? Put the black probe of your meter on the brown wires that attach to the body sheetmetal over under the heater controls (grounds) and put the red probe in each hole of the cannon plug. Does the meter jump? If it does, then the problem is probably in the wiring to your ignition switch that comes out the other side.

SweetE · 11-12-2003, 01:18 PM

No the Alt is not in the ignition circuit, however if it is not charging then you were running on your bat and ran it down. I also have an optima bat. in my E

Rot 911 · 11-12-2003, 01:29 PM

Sweet, if you read the initial post, the car won't even start with the battery charged! The alternator hasn't even come into play. Lynn my only concern is that we are "assuming" the battery is good. I don't know how many times I have made that assumption based on testing, only to find out the battery is bad. If you have another car, a battery switch might be in order.

SweetE · 11-12-2003, 01:43 PM

Kurt,
I absolutely agree with you. Sorry for any miss understanding on my part.
I think I kind of said that in my post and indicated a possible cause for the battery being dead ie. the alt..

Rot 911 · 11-12-2003, 05:18 PM

Or it could be that you have one or more corroded connections including grounds. I would clean all my connections running from the battery to the starter and the transmission ground strap.

304065 · 11-13-2003, 05:44 AM

Lynn,

Replacing the ignition switch is expensive, time consuming, and you have to get all the wires on in exactly the right connections or you will have even worse electrical nightmares. If you think that will solve the problem, go for it.

RoninLB · 11-13-2003, 06:38 AM

Quote:

Originally posted by LynnsABCs

I just hate to try to fix a problem by starting to replace components without pin-pointing what is actually wrong. That

IMO, the elec part of the ignition sw. is a problem waiting to happen in our cars if over 100k miles.

IMO, a solenoid jump momentary sw in the engine bay that bypasses all stock wires is relaxing........Ron

tkrefeld · 11-13-2003, 07:13 AM

I had the SAME problem in the 73. After 6 months of dicking around and headaches it turned out to be the PLUG behind the igintion switch was falling out. Sometimes things were fine and sometimes they were nothing. Cleaned and plugged it in and everything is fine. Had to drop the AC ducts to do it. Pain the ASS but it works now.