When I start up my 50 commander the temp guage slowly over 30 seconds creeps up to midway between cold & hot ..then when it hits midway it snaps up to hot in a split second...this is all with a cold engine.......does this sound like a heat senser or an internal gauge problem ? ..John
Announcement
Collapse
No announcement yet.
TEMP GAUGE
Collapse
X
-
I think that symptom points to either a bad gauge or the gauge is not getting a ground.
Power from the Key switch goes to the IGN terminal
on the gauge and splits to 2 coils inside the gauge.
Coil 1 is pulling the temp gauge needle to the right (hot) and Coil 2
is pulling it to the left (cold). There is also
a spring pulling it to the left too. The 2 coils are not the same
resistance so the "cold" coil (coil 2) has a weaker pull on the needle than the one going to the sender.
When things are working correctly, the sender has a high resistance
when its cold and low resistance when its hot. So, the current in
coil 1 is lower than coil 2 when cold and the needle is pulled to
the cold side. As the sender gets hotter, its resistance drops and
more current flows in coil 1 and it overpowers coil 2 and the spring so the needle is pulled to the hot side.
If coil 2 is open (broken) or the ground to it is lost, then coil 1 is
the only actor. With no power applied to the gauge, the spring keeps
the needle to the left, but when power is applied to the gauge,
coil 1 will have current and quickly overpower that spring without coil 2 there to keep it back.
I hope this makes some sort of sense [|)] I made a little diagram to
put with this using puctuation charactors but all the spaces I used got stripped off when I previewed it so I deleted it.
If the '50 gauges are like the '53-'55 ones, you can measure the resistance of each terminal to the car body (ground). Do that w/o any wires attached. You should expect to measure about 60 ohms from the ign terminal to the sender terminal and about 95 ohms from ign to ground. I suspect that ign to ground will measure open and its either broken inside or no ground.
Jeff in ND
'53 Champion Hardtop
Jeff in ND
-
My 52 did that, slowly up to normal temp, then BANG fullhot. I replaced the sending unit, same thing, replaced the gauge, and it's now fixed!
Jim"We can't all be Heroes, Some us just need to stand on the curb and clap as they go by" Will Rogers
We will provide the curb for you to stand on and clap!
Indy Honor Flight www.IndyHonorFlight.org
As of Veterans Day 2017, IHF has flown 2,450 WWII, Korean, and Vietnam Veterans to Washington DC at NO charge! to see their Memorials!
Comment
-
My Hawk does this also. I even replaced the gauge but with a used unit and it does the same thing. So, I guess I need to purchase a new unit. Nice explanation of how this stuff works, Jeff. I am electrically ignorant but have some understanding of it now. Thanks
Brent's rootbeer racer.
MN iron ore...it does your body good.sigpic
In the middle of MinneSTUDEa.
Comment
Comment