TR4/4A Voltage Stabilizer TR4A.

[mtlman8]

I went over the electrical system the other day, and Decided to Bypass the voltage stabilizer with an inline fuse (10 amp) is there any harm in this?

 

[Billm]

Your fuel gauge will not be quite as consistent (due to changing voltages) but no other changes should happen (assuming that the car is wired correctly stock).
You should not need the fuse since the power should only go to your fuel gauge.
BillM

 

[mtlman8]

Thanks bill.I had a fuel gauge issue to start with but was resolved after I bypassed the stabilizer.

 

[Billm]

They make "solid-state" voltage regulators but I just don't bother with them at all.
Bill

 

[LBCs_since_1988]

I believe the temp gauge would be affected as well.

 

[Billm]

I will definitely believe that- I have a mechanical temp gauge so don't think about that.
Bill

 

[mtlman8]

All gauges seen to work just fine, I don't know what the stabilizer was for, but since I've gone to an alternator everything works as it should.I put the inline fuse in as a "just in case" sort of thing because I was not sure.

 

[HerronScott]

Aaron's right. Both the fuel gauge and temperature gauge will be affected.

The regulator supplies 10V so both gauges should read high running from battery/generator 12+ volts.

Scott

 

[mtlman8]

So without the stabilizer, It will run at 12 volts as apposed to 10 volts appearing higher at both gauges?

 

[Billm]

Yep-

 

[mtlman8]

I just ordered a new one from Moss... Thanks guys.

 

[TR3driver]

It wouldn't be difficult to recalibrate the gauges to work on 12v; the problem is that the battery voltage is nowhere near constant. Idling at a stoplight with the headlights and heater on, it can easily droop to 12.0. Running down the road on a cold day, it should be closer to 14.0 volts. The gauges respond to the square of the voltage, so it makes a noticeable difference on the reading. That's why the original setup used the "stabilizer".

I did something similar to what is shown at https://www.britishv8.org/Articles/MGB-Voltage-Stabilizer.htm; except my NTE1953 didn't seem to regulate properly without some capacitance on the input and output.

 

[dklawson]

I also put together a PDF on troubleshooting and replacing the stabilizer.
https://home.mindspring.com/~purlawson/files/SmithsVoltageStabilizer.pdf

Like Randall said, with the charging system working the gauges will really see closer to 14V. Since the stabilizer is supposed to supply 10V, that means your gauges will be operating on as much as 40% too much voltage. That means higher current flow, higher gauge readings, and... more heat.

So bypassing the stabilizer will cause the gauge readings to be high and it can potentially shorten the life of both the gauge and sending unit.

The easiest method of replacement is to buy Moss's solid state stabilizer. I think they are now under $15 each. The DIY method shown in my PDF and in Randall's link is another possibility. However... the absolute cheapest solution is to solder wires directly to the 7810 regulator chip, cover all the leads with heat shrink tubing. Then terminate the wires with crimp terminals and use the mounting hole on the chip to attach it to a metal surface behind the dashboard. On the Spitfire I ran one chip per gauge instead of one chip for two gauges. The chips are cheap from sources like Mouser.com and if you can solder this gives you an inexpensive and long life repair.

The picture link below is for the simplest implementation of a 7810 chip as a voltage stabilizer.
https://www.adocars.com/elf-ado/elf/elfimages/v-reg.jpg

 

[tomshobby]

Here is an option that has been in my car for a couple years.
https://www.bits4brits.net/Stabilizer.html

 

[Adrio]

and if you have positive ground on your car use the 7910 rather than the 7810.