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MG MGB Technical - voltage stabilizer... where?...

Hi

I have a UK 1977 roadster. I understand from the archive that the voltage stabilizer should be attached near the air vent next to the driver's knee(passenger's knee in US). Should it be easy to see?

I've had my head in the footwell for about 30 minutes and I can't for the life of me see anything which might be it or follow the wiring from the temp/fuel gauge to it.

I am starting to suspect a previous owner (my car's had seventeen according to the log book!) bypassed it - in which case my high temp readings and tendency to run out of petrol may, at least in part, be due to the gauges getting 14V and not 10V.

It's not very obvious that the temp/fuel increases with engine speed but the gauges are so slow to respond it's hard to tell.

Should I look harder - in which case can somone point me to a more specific place - or should I have seen it by now and it's probably missing?

cheers for any help
Darren
D Lewis

On earlier cars...mine's a 69....in the U.S. it is against the firewall just below the defroster vent on the driver's side (left side). Would suspect it would be on the right side in the U.K. as the green and light green wires from it go into the instrument cluster so it must be near them.
J.T. Bamford

Stabilizer http://www.mgcars.org.uk/electrical/stabilizer.html
The above link might help.
Kevin Pearce

Thanks for the pointers...

However, I'm afraid I don't really recognise the part of car shown in the photo at the website referred to (great site - will probably be making a semiconductor replacement even if I find I do have a stabilizer)

Can anyone quickly suggest what angle it was taken from and what its rough scale might be - it all looks very different upside down with the dash on and wires trailing everywhere. I am not sure I even see, what appears to be, a big black rubber grommet type thing shown in the photo - would this be on a UK 77 roadster as it looks a good landmark?

thanks again
Darren
D Lewis

Tech Tips

John Twist tech tips:

VOLTAGE STABILISER: The voltage stabiliser powers two instruments at the most: Petrol gauge and Temperature gauge. Test this unit by inserting your 12v test light into the GREEN/BLUE temperature transmitter wire at the front of the engine. With the key ON and the test light earthed, the light will glow for about 20 seconds then begin winking ON OFF ON OFF like a slow turn signal. The stabiliser rarely fails but sometimes comes loose, which causes these instruments to read high. A failure of ALL the dash gauges is simply a dirty fuse (third down) in the fusebox.


If you run this test you will find out if you have a stabiliser or not or if the stabiliser is your problem.
Kevin Pearce

Darren,
the big black grommet is behind the brake and clutch master cylinders. If you take it out you can do/undo the banjo bolts connecting the hydraulic lines going to the cylinders.
So: on you car the stabiliser should be just to the right and up from your pedals. I am not 100% sure on this as I only have experience with CB Bs. Size of the stabiliser is +/- 1 1/2"
HTH,
Rufus
R Pool

Hi all

Thanks for the help - have done the test-lamp test and it seems to indicate that I indeed don't have a stabilizer...

P.S. Quote from Rufus -

"the big black grommet is behind the brake and clutch master cylinders. If you take it out you can do/undo the banjo bolts connecting the hydraulic lines going to the cylinders."

Thanks for the tip - although I wish I'd heard it last week before I sawed through the brake pipe to get the master cylinder out!

Darren
D Lewis

Darren,

In my 73 GT the stablixer was installed on one of the nuts that holds the temp gauge in to the dash. If it's not working (missing) I believe the temp and fuel will read lower than the actual reading.

Regards,
Dennis
Dennis Hosier

No, it is higher. The way the stabiliser works is by disconnecting the supply voltage (12.8v to 14.5v depending on circumstances) from the gauges momentarily every second or so, so the 'stabilised' (a wonderful misnomer) voltage averages less than the supply voltage, at about 10v. If the stabiliser has been bypassed, or is not screwed to the shell properly to pick up a ground, the full supply voltage is connected to the gauges all the time and so they read high. The ground is required because the stabiliser is a thermo-mechanical device with a heating coil wrapped round a bi-metallic strip, which disconnects the input voltage from the output terminal when the strip is heated and bends. The heating coil is wired between the output and ground. On a UK 73 it is screwed to the bottom edge of the firewall by the steering column. On a UK 80 the indicator and hazard flashers are in that location, the stabiliser is above them right at the top of the firewall and much more difficult to get at.
Paul Hunt

Thanks all, mission accomplished.

I did in fact have a non-working stabilizer which was careefully hidden behing the wiper motor. Having recently overhauled this very motor and removed/regreased the wiper drive cable I must admit I suddered at the thought of having to do anything more in that area.

Anyhow, I now have a working 10v semiconductor regulator (sorry - I'm happy to forgo originality for convenience and cost) and all is rosey in the garden of gauges.

Darren

PS I've said it before, but once again, let's be honest, this BBS really is top dollar for quality advice, thanks all - if only there had been a similar site directed to the 1995 Ford Fiesta Frascati (with passenger airbag) then life with my previous car would have been so much better...

D Lewis

This thread was discussed between 27/08/2004 and 31/08/2004

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