260Z gets a Frontier alternator

[Zed Head]

34 minutes ago, SteveJ said:

If the brake check warning lamp works with the ZX alternator, I don't see why it wouldn't work for the Frontier alternator.

It's not the alternator it's the wiring from the external VR in 1976.  If you follow the two main wiring suggestions on the internet, one disables the brake check light, the other causes the relay to be on al the time, draining the battery.  The wiring diagrams don't work for 1976.  The Frontier alternator is just like a ZX alternator except for the type of electrical connections.

[SteveJ]

2 minutes ago, Zed Head said:

It's not the alternator it's the wiring from the external VR in 1976.  If you follow the two main wiring suggestions on the internet, one disables the brake check light, the other causes the relay to be on al the time, draining the battery.  The wiring diagrams don't work for 1976.  The Frontier alternator is just like a ZX alternator except for the type of electrical connections.

Thanks, I don't recall seeing that issue discussed.

[SteveJ]

5 hours ago, Zed Head said:

It's not the alternator it's the wiring from the external VR in 1976.  If you follow the two main wiring suggestions on the internet, one disables the brake check light, the other causes the relay to be on al the time, draining the battery.  The wiring diagrams don't work for 1976.  The Frontier alternator is just like a ZX alternator except for the type of electrical connections.

I looked at the brake warning light circuit. The relay is energized by the neutral. I'm not sure why it is important to have the brake light illuminated on only while the alternator is turning. Do you know?

According to the wiring diagram, there is a white wire that goes to the alternator. That should be the source for the sense wire. There is also the green wire near the VR that goes to a condenser. That should be the source for the lamp wire. That could also be connected back to the yellow wire for the brake light relay.

It wouldn't be quite as simple as cutting some wires and splicing, but it could be made to work with the ZX alternator or Frontier alternator. Unplug the old voltage regulator to prevent problems, and you're done.

[Captain Obvious]

30 minutes ago, SteveJ said:

The relay is energized by the neutral. I'm not sure why it is important to have the brake light illuminated on only while the alternator is turning. Do you know?

I didn't study the 260 system, but I believe it's supposed to be more "dead man".

I think the light is supposed to come on if the alternator is NOT spinning. The theory as I understand it is that you are being told that you may not have power brakes anymore because you have lost your source of vacuum energy.

Are you sure the brake warning lamp doesn't use NC contacts? I know it does on the later years like my 77. That's why the brake warning relays always burn up. They get tired of being powered every single second the engine is running.   

[SteveJ]

I think  you're right, Bruce. So, it would take more modification, like using a 78 oil pressure sender to get a signal that the engine died.

[Zed Head]

It also comes on if the brake system pressure differential switch is actuated.

I thought that the word "check" referred to the fact that it went on as soon as the key was turned on, confirming that it worked.  "Checking" the light, not the system itself.  Otherwise they could have just had the pressure differential switch complete the warning light circuit, and the light would never light unless there was a problem.  You'd never know if the light worked or not.  I did find that it was a convenient warning that your engine had died though.

I ran a tap line over to my fuel pump power line next to the seat to power the relay.  Which is controlled by the AFM contacts and fuel pump relay on a 76.  

My original comment was more about the fact that even with somebody else's instructions you still have to make sure it will work for your particular situation. 

 

 

[SteveJ]

Here's how the brake warning light circuit works in the 76:

The green wire (ignition on) goes to the brake warning light in the speedometer. It comes out as green/yellow. There are 3 branches for the green/yellow wire.

1. One branch goes to the brake pressure differential switch. The switch grounds the circuit when there is a problem.
2. The second goes to the parking brake. The wire is grounded if the parking brake handle is lifted.
3. The third branch goes to the brake warning lamp check relay where it goes through a normally closed contact that connects the wire to ground. The relay coil is energized by the neutral from the alternator, opening the contact when the engine is turning the alternator fast enough. The benefit is that it does light up if the engine stops turning when the key is on, as @Captain Obviouspointed out.

This wouldn't be a plug-and-play solution, but here is one idea:

1. Connect the yellow wire to the switched source. 
2. At the brake warning lamp check relay re-wire the circuit so that the yellow wire goes to the 85 and 87 contacts of a time on delay relay. The 86 contact would be grounded, and the 30 contact would go to the same pin on the brake warning lamp check relay that the yellow wire formerly connected to.

The warning light would come on for a few seconds when starting the car and go out. The downside is that it would not respond to engine dying.

Solution 2:

1. Connect the yellow wire to the switched source. 
2. Replace the oil pressure sending unit with a 78 style. Run the normally open contact at the sending unit to the brake lamp warning check relay and put it on the ground for the coil. (If the relay is grounded on the chassis, the relay would need to be replaced with a modern SPDT relay.)
3. The green/yellow and ground wires would stay on the normally closed contacts.

At least the old functionality would be maintained.

Solution 3?: (I'd have to do some testing.) ZX alternator only

1. Connect the yellow wire to the P terminal.
2. Done.

I'll see if I can't bench test #3. I have a spare internally regulated alternator handy. I'll need to give it the lamp and sense signals and spin the alternator with a drill to see if I can get good voltage out the P terminal.

 

[Zed Head]

26 minutes ago, SteveJ said:

Solution 3?: (I'd have to do some testing.) ZX alternator only

1. Connect the yellow wire to the P terminal.
2. Done.

I'll see if I can't bench test #3. I have a spare internally regulated alternator handy. I'll need to give it the lamp and sense signals and spin the alternator with a drill to see if I can get good voltage out the P terminal.

The P terminal would be interesting.  I don't really know how it works, I've seen it called a revolution counter or tachometer.

Solution #4 works just fine for a 76 though.

1 hour ago, Zed Head said:

I ran a tap line over to my fuel pump power line next to the seat to power the relay.  Which is controlled by the AFM contacts and fuel pump relay on a 76.  

 

[Zed Head]

The internet says it is unrectified.  How will you rectify that problem?

https://www.autoelectrics.net/alternator_terminal_identification.html

Edited March 1, 2022 by Zed Head

[SteveJ]

1 minute ago, Zed Head said:

The internet says it is unrectified.  How will you rectify that problem?

https://www.autoelectrics.net/alternator_terminal_identification.html

I thought it might be unrectified. The first test is to see if it registers DC voltage on a voltmeter. I was also going to test it with a SPDT relay. If it pulls in the coil and holds, it works. I might even play with using a diode to make it a pulsed signal if it is sinusoidal.  I could even do a test rig in my 240Z to see if it holds up for some trips. I could rig the contacts for the relay to a taillight socket with an LED bulb to see if it stays bright. A dim LED would indicate the contacts are cycling. Anyway, I've put a DC coil in an AC circuit before. The sound isn't pretty.  

Good point on the FPR. That sounds like the preferred solution if the P terminal doesn't pan out. The only advantage of the P terminal is that it you wouldn't have to do much outside of back the pin for the yellow wire out of the the T connector and put it in a single pin connecter.

[SteveJ]

So I turned the alternator with a drill and probably spun it faster than it should go. The bearings are shot. All in the name of science! 

I would see peaks around 6VAC on the P terminal, so it is definitely unrectified. The FPR signal for the brake warning lamp check relay is probably the way to go.

[Captain Obvious]

4 hours ago, SteveJ said:

So I turned the alternator with a drill and probably spun it faster than it should go. The bearings are shot.

You're kidding.

How fast does your drill go???