Well, I finally have the car running but now it appears I have an electrical issue.  When the battery has a full charge the car starts just fine but the alternator gauge has a slight negative reading.  After running for a bit and shutting it off, the car tries to start but since it has been running on the battery there's not enough spark.  I have a brand new alternator that clearly isn't charging the battery when the car is running.  Any suggestions as to what the problem could be?

The "relay" is the voltage regulator. The W/B wire is for the field. It should inject current into the alternator when the voltage is low. A failure to produce an output from the alternator could be a problem within the voltage regulator or the alternator.

What makes you think I don't like that grotesque abomination called the Interlock Relay Unit? Have you ever buckled up an inanimate object in the passenger seat because the car would not start otherwise? Seatbelt interlocks came from a push by Ford to make itself look good to the NHTSA about getting people to use their seatbelts more. While Ford had already designed and debugged their system, the NHTSA mandated the implementation of a seatbelt interlock for all cars in the 74 model year. With the relatively short notice most automakers implemented the rules poorly. The NHTSA quickly retired the rule. Here is some reading on the subject: https://www.allpar.com/threads/the-return-of-the-seat-belt-interlock-crazy-rule-or-money-saver.236643/. People found ways to defeat these systems because a faulty interlock would make it where you couldn't drive your car. There is an emergency button under the hood on the passenger fender. There's a picture below. In its early life, the button was red.

It's an annoyance to have intact, but it won't affect charging.

2 hours ago, SteveJ said:

What makes you think I don't like that grotesque abomination called the Interlock Relay Unit?

LOL!  

Now that I know what you're talking about I disconnected that thing years ago.  I assume that's all it takes to bypass it?  As for my problem, the voltage regulator and alternator are new.  I haven't tried restarting it since I replaced the voltage regulator as it already had a new alternator.  I'll attempt to start it again this weekend and advise if I need further troubleshooting tips.  Hopefully it was an issue with the 47 year old regulator.

New problem.  When I first tried to start it it was firing but wouldn't stay running.  I had to turn it over several times which was hard on the battery so I let it sit for a bit and put the charger on the battery.  After it had recharged I tried again and now I have no spark at all.  I measured the voltage on the coil and in the start/on keyswitch position I'm only getting 5 vdc.  I assume this is insufficient and I'm baffled as to what could have happened.  It was starting just fine prior to troubleshooting the alternator issue and replacing the voltage regulator, neither of which should affect it's ability to start.  Any ideas as to what could have gone wrong and how to troubleshoot this new problem?

17 minutes ago, Dolfinz said:

New problem.  When I first tried to start it it was firing but wouldn't stay running.  I had to turn it over several times which was hard on the battery so I let it sit for a bit and put the charger on the battery.  After it had recharged I tried again and now I have no spark at all.  I measured the voltage on the coil and in the start/on keyswitch position I'm only getting 5 vdc.  I assume this is insufficient and I'm baffled as to what could have happened.  It was starting just fine prior to troubleshooting the alternator issue and replacing the voltage regulator, neither of which should affect it's ability to start.  Any ideas as to what could have gone wrong and how to troubleshoot this new problem?

Check the voltage at the battery while cranking. I'll bet it's pretty low, too. You don't say how old the battery is. Maybe you did earlier, but I'm not going back to see. The plates could be sulfated, they can still have adequate voltage while sitting, but they don't have the surface area for the electron flow needed during cranking.

The battery is also fairly new.  I checked the voltage while cranking and it was 12.3vdc.  The motor is turning over just fine but there's no spark from the distributor at the plugs.  Not surprising since there's only 5vdc at the coil.  What could be causing the voltage at the coil to be so low?

34 minutes ago, Dolfinz said:

The battery is also fairly new.  I checked the voltage while cranking and it was 12.3vdc.  The motor is turning over just fine but there's no spark from the distributor at the plugs.  Not surprising since there's only 5vdc at the coil.  What could be causing the voltage at the coil to be so low?

I appreciate your willingness to go back and test. 

Let's look at the coil and work back. Fortunately, it's not that difficult to trace.

For stock wiring there should be a white/black wire from the coil to the ballast resistor. There is a black/blue wire attached to the ballast resistor on a different terminal. The black/blue wire goes to a 3 wire/4 position plug and through the engine harness to connector C-5 where it stays black/blue going through the dash harness. The black/blue travels over to the ignition switch where it is energized when the key is in the start position.

So what could cause the voltage to drop?

1. The ignition switch could be wearing out.
2. There could be corrosion at one of the three connectors
3. There could be a bad connector at the ballast resistor or failed ballast resistor.

So what can you do to test?

1. Measure resistance at the ballast resistor between the white/black wire and black/blue wire.
2. Alternatively, you may want to test the voltage to ground at the black/blue wire at the ballast resistor with the key in START. If it's 12+, then it's probably the ballast resistor. If it's low, you know it's before the ballast resistor.
3. Visually inspect the connectors. If they need to be cleaned, a little vinegar on a q-tip can clean off corrosion at the connectors.
4. Disconnect the connector on the back of the ignition switch and test the resistance with the key in START between the terminals where the black/blue wire and the white/red wires would go.

This is excellent information, thanks.  I checked the voltage at the ballast resistor blk/blu wire and it was 7.2vdc with the ignition switch on start.  I checked the wht/red wire at the ignition switch and it was 12.2vdc.  When I turned the switch to start, the wht/red was constant but the voltage at the blk/blu was 7.2vdc.  I removed the ignition switch assembly and checked the contacts resistance at less than 1 ohm.  While I wouldn't think this is indicative of a bad switch I am ordering one anyways due to the voltage drop.  I also checked the resistance between the wht/blk and blk/blu on the ballast resistor and got about .1 ohms.  Is this correct?  I will follow up once I receive the new switch.

The switch contacts should be pretty close to zero. The resistance at the ballast resistor is fine. You don't want the resistance to be too high because that would be a voltage drop.

It does appear that you are losing voltage somewhere, depending upon where you measured the 7.2V on the black/blue wire. Was it at the resistor or the ignition switch? Again, look for corrosion at the connectors for where the dash harness plugs into the ignition switch.

The 7.2v was at both the resistor and the ignition switch terminal connector.  I didn't see any corrosion at this connection.

Then if your technique was good, that might indicate wear within the ignition switch. Did you order the full switch with key or just the module in the back of the switch?

The 7.2 volts could mean a grounded circuit, either after the ballast or the coil, maybe at the ignition module or along the way to the module. If you had points I'd say check that your points weren't closed.

Edit - p.s. the coil, or the ballast, or wires in the vicinity should be warm if current is flowing, giving that big of a voltage drop.

Just spitballing.  Hard to get a good grasp on the overall picture.

Edited November 9, 20213 yr by Zed Head