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TR4A Wiring

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rsanford Raleigh Sanford
Millington, Tennessee, USA   USA
Hello. Trying to educate myself on TR4A wiring and auto wiring in general. I think I would have better luck with Chinese. My A-4 fuse blows almost immediately upon turning ignition to on. I have a wiring diagram and see the first stop is the Gauge Voltage Stabilizer. Upon my neighbor's advice, in my ohm setting I touched the red to the B terminal and the black to the E button and it went to 0, which he said means the Stabilizer is bad. I am attaching photo of set up. Several questions. First is what my neighbor said correct. Second, is the setup correct and third, when I went to check this, the side of the Stabiilzer by E held down by a tab was loose from the tab. Would that affect the ground function or would it still be grounded by the main screw holding it to the car. Thanks as always. Raleigh.

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TR3driver Randall Y
Confusion, Los Angeles, USA   USA
First you need to disconnect the green/black, to eliminate the possibility of a short farther down the line. Then IF it was the ohms X1 scale, then that would probably indicate the stabilizer is bad. But any other ohms scale would read 0 (or too close to tell the difference) for a good stabilizer. Plus, they don't usually fail that way (open is more likely). So I would double-check that.

Also, your photo kind of looks like it is wired wrong. Both green wires need to go to the tabs attached to terminal "B"; only the green/black should be on terminal "I".

One trick that can be helpful is to take an old headlight bulb and temporarily wire the filament that didn't burn out across the fuse holder. Now instead of blowing the fuse, a short will light the bulb brightly. The bulb will only pass about 5 amps, so there is no harm to the wiring. This doesn't work in all cases, but will often do the trick.

Then you can, for example, pull the green wires off the stabilizer and see if the bulb goes out. If so, you're closing in on the problem. Try pulling off the GB wire, and the G wire to the heater switch.

If the bulb stays on, the problem is somewhere else.

I'm not positive, but I believe the rivet at "E" is the connection to the internal mechanism. So a bad or loose connection between it and the case will cause the stabilizer to not work right. (Usually, it passes full 12v all the time and the gauges read too high.)



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

rsanford Raleigh Sanford
Millington, Tennessee, USA   USA
Thanks Randall for the info. You are right. In all the disassemblies and reassemblies, the wiring was not correct. So the GB wire goes from terminal I to the gauges with the lower voltage. And the double green and single green on terminal B. Does the single green go to the heater and is one of the double green bringing voltage in and the other carrying it on to the lights, wipers, etc. Since I did have it wired wrong with the single green on I and the GB on B, would that be causing the problem or is there a problem somewhere else and I need to just start trouble shooting as you have directed. Raleigh.

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TR3driver Randall Y
Confusion, Los Angeles, USA   USA
The diagrams I've checked don't clearly define which green wire is which; but the factory diagram shows the heater as optional. So I'm assuming that the individual green wire is the heater.

Being wired wrong might damage the stabilizer, but isn't likely to cause it to short out. Internally, it has a pair of contacts, one of which is mounted on a bimetallic strip. There is a heater wrapped around the bimetallic strip, when the strip gets hot enough it moves and opens the contacts. The heater is wired from "I" (the output) to "E" (ground). Usually, they fail because either the heater burns out (causing it to pass voltage all the time), or the contacts get burned/dirty and it doesn't pass voltage at all. BTW, that means the output is never "10 volts", but rather switches between full battery voltage and nothing such that the average output is 10 volts. If you hook a test light or voltmeter to the output, you can see it flash on and off.

Except of course for the modern "solid state" replacements, which are totally different inside. They use a simple linear regulator IC to provide a smooth 10 volts.

I still think it unlikely that the stabilizer is the cause of your blown fuse. The loose rivet might be cause to replace it; but I would want to chase down the short first. In theory, the solid state replacements should be able to deal with the GB wire being shorted without damaging the IC. But in practice, it doesn't always work out that way. We've also discussed that sometimes they don't work right.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

rsanford Raleigh Sanford
Millington, Tennessee, USA   USA
Thanks again. I may be misunderstanding but my diagram shows the heater wire coming off the B terminal at I assume full voltage and only the wire to the gauges coming off terminal I at stabilized voltage. Is this right.

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
Yes, that's right. The stabilizer output is only for the fuel and temp gauges. The stabilizer just serves as a junction for the wire to the heater switch.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

rsanford Raleigh Sanford
Millington, Tennessee, USA   USA
Thanks. I will update as I proceed.

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rsanford Raleigh Sanford
Millington, Tennessee, USA   USA
Alright, making some progress. Figured out brake light circuit and disconnected everything else and brake lights work. Next going for turn signals. When I place the lever for left turn, the amber side marker flashes but the clear lens doesn’t do anything. That could be a bulb issue and I will check further. However, when I turn right, both flasher lamps flash but none of the right side marker lights come on. Any thoughts on where the problem is. Thanks. Raleigh.

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
In reply to # 1491771 by rsanford However, when I turn right, both flasher lamps flash but none of the right side marker lights come on.
I don't understand that statement. Where are the "both flasher lamps" ? Should be only a single indicator lamp on the dash, that flashes for both sides. The other lamp is the "ignition warning lamp", aka generator indicator.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

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rsanford Raleigh Sanford
Millington, Tennessee, USA   USA
I may be calling it wrong but I'm talking about the two small lights in front under the headlights.

TR3driver Randall Y
Confusion, Los Angeles, USA   USA
Sorry, my mistake. Thanks for the explanation. Sorry, I can't help with where the most likely wiring mistake is, but obviously you have at least one.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

rsanford Raleigh Sanford
Millington, Tennessee, USA   USA
Got it figured out. I should have thought and looked more before asking that last question.

rsanford Raleigh Sanford
Millington, Tennessee, USA   USA
Randall, I pretty much have my A-4 circuit straightened out. You were correct. I did have the gauge wire on the wrong post and corrected that. I did not connect the single green wire assuming it goes to the heater and disconnected the wiper. Now my turn signals work and brake lights work. I will get to the bottom of the heater and wiper at my leisure since I do not have a top and for the forseeable future will only be driving on days I don't need a top or heater or wipers. My temp gauge works finally and the fuel gauge should as well. Thanks again.

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