TR6 TR6 Electrical Question/Suggestions

[Tim Tucker]

HI guys.

I have had my TR6 for just over a year now. Very little electrical worked correctly when bought: mis-wired or bad sockets mostly. Everything 'basically' works now and my main isuue is: the IGN light that won't go off!

I installed a new battery when bought and repaired the Lucas 17acr alternator (new regulator and 1 diode). I have driven it without having to jump it off ever since.

Last Friday I replaced the factory AMMETER with my Fluke. Here is what I got:
Lights ON (high beam):
700 RPM (per electronic tach) – discharge condition
1200 RPM – 0 amp condition
above 1200 – charge condition

Lights OFF (performed after lights on test-slight discharge of battery may have occurred):
700 RPM – 2A charge
over 700 RPM – more charge

Voltage measured at Battery:
12.2 VDC and dropping with lights ON(car at idle);
12.4 VDC and rising with lights ON(1200 rpm);
12.84 VDC with lights off(idle)


TEST #2 What voltage does the IGN light see?

Fluke voltmeter hooked as shown (red to alternator, black to the white wires on the back of the ignition switch).

Reading at idle(700): -.2 to -.5 VDC very bouncy, idiot light barely lit
Reading as RPMs increase(above 1200): +3VDC, idiot light bright

Thanks if you took the time to read this post...Smile Any advice would be welcomed. I realize the best approach would be to replace the Lucas alternator. I just don't fully understand why the IGN light is lit. Is it the regulator that is causing this? I have checked the battery voltage several times over the year and it is always good.

Last question:
Is there a trick to getting the knob off of the dash illumination rheostat? I don't seem to find a button to depress.

Thanks,
Tim

 

[TR3driver]

Tim,

Sounds to me like the main problem is that you have the wrong bulb in the dash light. It should be a 12v bulb (2.2 watts as I recall), meaning it should be just barely lit (if at all) at 3 volts.

Have you checked for excessive voltage drop in the charging circuit ? That's one reason for the light to glow dimly. Try connecting your voltmeter between the alternator output and the battery terminal, then rev the engine to roughly 3000 rpm. The voltage should not exceed 0.5v.

Also check the ground path, from the alternator case directly to the negative terminal. With the engine again at 3K, the voltage drop should be less than 0.25v.

 

[hondo402000]

Maybe take the Alternator off and take it to a repair shop and they can tell you if it is working properly

 

[poolboy]

Ditto what hondo said. The sales clerks at the auto part stores may or may not know how to interpret or even perform the test. Whereas, Alternator and Starter shops do that for a living and don't spend most of their work day looking up part #'s and running a cash register.
About the rheostat knob, its probably "hot glued" in place. The rheostat generates heat when the lights are on , a lot of heat. I think that heat kind of molds the knob around the shaft.
A fellow on another Forum suggestes a hair drier may help loosen it.
I guess I was lucky, mine came off pretty easy. You might want to protect the dash finish if you have to pry it off, with a thick piece of paper or the like.

 

[TR3driver]

One more thought : you showed you checked from alternator terminal to ignition switch ... is there any chance the dash lamp is not wired correctly ?

I'd also want to check what happens at higher rpm with the battery charged. YOu should see the battery voltage rise to slightly over 14 volts, but not as high as 15.

 

[Minesweeper]

Hi Tim -- been trying to post this on the 6-pack forum all day but it won't go, so I'll post here:

On your ignition light question, seems to me the light is working correctly. As I understand it, the light shows the difference in voltage between the alternator side and the battery side of the charging circuit. It should extinguish when the two sides equalize at 14 or so volts. You are never getting to that point, so the light doesn't go out. The fact that it gets brighter at higher rpm indicates that it is the battery side that is faulty (i.e., at idle you have a dim light because the low battery side voltage is nearly the same as the low alternator output; at higher rpm the light is bright because the alternator output is substantially greater than the battery side). I'd get the battery tested as a first step.

That's my view of it. I could be dead wrong, but you did ask for *any* advice! :laugh:

 

[Tim Tucker]

Thanks for all of the responses.

Randall: remember the temperature guage post? I adjusted my guage to match these newer transmitters. The lower adjustment seemed to work in my case, as the upper was set to its lowest. Anyway, I now have a guage that is dead on center at 180F and just outside hot at 200. Your tool would definitely be the way to go. Thanks for your input.

First, I checked the bulb and it is a 12V 2.2W

Second, voltage across battery terminal: 14.1 VDC@3K RPM

Third, the numbers I got for the two tests (lights on high beam) were .4VDC for step B, and -.02 for step D. NOTE: the negative lead of the DVM was connected to the proper battery terminal for both tests.

last, the dash lamp appears to be wired correctly. I did a continuity test between the brown/yellow and the outer portion of the bulb's socket(.1 ohms), the brown/yellow showed no path to ground when disconnected from alternator. I also did the same test with the white wire and the center conductor of the bulb's socket(.1 ohms), again the white wire showed no path to ground when the rest of the circuit was disconnected from the fuse block (400 ohms when it was not).

I removed my heater box for easy access to all of the instrument wiring. I have not found any patch jobs. I was surprised.

Thanks for the advice.
Tim

 

[TR3driver]

So, you know the wiring to the alternator is OK, and the alternator itself appears to be working properly. The voltage drop through the alternator diodes, switch and ignition circuit might be a little higher than nominal; but it still seems to me that the main question is how a 12v bulb is lighting "bright" with only 3 volts applied. I just checked using a TR3 style bulb, and it just barely glows at 3 volts, looking directly at the filament. It would be invisible, except at night, if mounted in the dash lamp.

I'd replace the bulb. If that doesn't solve the problem; try to monitor the voltage right at the bulb holder with everything connected and the bulb lit brightly.

You could also go looking for the rest of that 3 volts. You've found 0.4v of it in the charging circuit; and there's probably another volt or so in the main diodes inside the alternator. But that still leaves 1.5v unaccounted for, which seems high for the drop through the ignition switch and wiring. I would probably check at the alternator next (compare the output terminal to the IND terminal). Then look at the drop across the switch.

PS, in either case, if the drop is that high, chances are the unit is dying. Start looking for a new one.

 

[hondo402000]

you should upgrade to a 55 amp alternator, once you start adding radios amps, halogen head lamp, running a electric cooling fan, fog lamps,,, you will need the extra power, the bosch unit on a 1980 ford fiesta unit has the correct plug, you will have to fiddle with the mounting spacer but well worth it

 

[Tim Tucker]

That appears to be where I am headed...)
Tim

 

[TR3driver]

the bosch unit on a 1980 ford fiesta unit has the correct plug,

Just for clarity, most 78-80 Ford Fiestas did not have Bosch alternators, and the Motorcraft unit does NOT take the same plug or mountings. Only cars with AC or "heavy duty electrical" had the Bosch.

When we did the conversion on a friend's later TR6, it bolted right on, no fiddling required, but YMMV.

And purely as a side note, IMO that connector is a weak point. I've seen them overheat and fail, especially when running increased current through them. If it were my car, I'd be looking for a nice, solid, bolted connection.

 

[TR3driver]

Oh yeah, and if your problem is excessive voltage drop through the ignition switch or ignition wiring, a new alternator isn't going to help.