Bob MGT wrote:
>
> In a message dated 1/19/98 5:34:45 PM !!!First Boot!!!, dswope@ix.netcom.com
> writes:
>
> > Hi folks. A member of our local MG club here in Austin TX has a
> > problem, and has asked me to post it for him in hopes someone can give
> > him some advice! I have told him how good you all are at giving advice!
> >
> > "A couple of years ago, I broke the little spade connector off the
> > temperature sensor on my '76 B Roadster. I got a new one at a local
> > parts house, but after I installed it, the temp gauge pegged on "hot" as
> > soon as the engine warmed up (the engine was definitely *not*
> > overheating). I took it back for a replacement, which they provided,
> > and I got the same result. I got out my soldering iron and tacked on a
> > glob to the old sensor that I could get an alligator clip on, modified
> > the wire to end in a clip, reinstalled the old sensor, hooked it up, and
> > things were back to normal. Fast forward to the present. I had to
> > replace my head gasket, so I took the head in for a valve job, and I
> > forgot to remove the sensor. The machine shop managed to whack it
> > beyond all possible repair, so I ordered a new sensor from Victoria
> > Limited (the unit specified for my model year), and I'm back to the same
> > problem. Pegged on "hot" when the engine comes up to normal temp.
> > Since I've just had the cooling system all apart, I am reticent to drive
> > around very much with no data from my temp gauge -- any ideas?"
> >
> > Responses can be sent to me, and I will pass them on, or to Gordon Gunn
> > at ggunn@texas.net
> >
> > Thanks folks!!
> >
> > Donna Swope
>
> Hi Donna:
>
> I just put a new one on my '71 B. I purchased it from Victoria British and it
> works fine.
> First time I've ever seen the gauge get up to normal.
> When these things go bad they usually cause the gauge to read low. The room
> temperature resistance of the new one measured 830 ohms. The resistance should
> go down as it gets hotter. Another thing to check is the bi-metal voltage
> stabilizer.
> It is supposed to provide a regulated 10 Volts for the gauge circuit. If it is
> bad it could
> be putting out full battery voltage (12V engine off, 14V engine running) and
> that will make
> the gauge read high. A good way to check the voltage stabilizer is to unplug
> the wire
> from the sensor and measure the voltage from the wire to ground. It may bounce
> around
> a little, but it should average 10 Volts.
>
> Bob Donahue (Still stuck in the '50s)
> EMAIL - BOBMGT@AOL.COM
> 52 MGTD - under DIY restoration NEMGTR #11470
> 71 MGB - AMGBA #96-12029, NAMGBR #7-3336
If you have the standard bi-metal 'stabiliser' you will find the output voltage
swings from 0v to 12v two or three times a second, unless the case of the
stabiliser is not at ground in which case (ho!) you will see a steady 12v. The
case should be at ground.
PaulH.
|