How to install temp gauge while still keeping dummy light?

Northcoast300h

Northcoast300h

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1970 300 originally came with dummy light, but I wanted both dummy light and gauge. So I did this over 20yrs ago. Worked fine until this fall when I think sending unit or gauge became very inaccurate. Gauge sending unit is on top. Original dummy light switch is on side not in pic.

I'd like to do it correctly this time rather than my redneck products from Home Depot. Anyone know what part numbers I can buy to do it correctly? I want the dummy light to work too. Thanks.

IMG_E4547.JPG
 
Aim for brass fittings next time. Might not be quite so bulky.
 
Are the sending units 1/2" pipe thread? I'm not sure if there was ever a "factory" manifold connection for two sending units but you could build a solid setup from off the shelf automotive style brass fittings.
 
There MIGHT have been something on the Imperials with the "Master Gauge Light" which came on when the gauges got "out of the normal range"? Which would have meant the normal sensor to run the gauge and also a sending unit "switch" to run the light.
 
Northcoast300h said:
1970 300 originally came with dummy light, but I wanted both dummy light and gauge. So I did this over 20yrs ago. Worked fine until this fall when I think sending unit or gauge became very inaccurate. Gauge sending unit is on top. Original dummy light switch is on side not in pic.

I'd like to do it correctly this time rather than my redneck products from Home Depot. Anyone know what part numbers I can buy to do it correctly? I want the dummy light to work too. Thanks.

View attachment 570903
Click to expand...
Redneck isn't a bad thing.
 
It's worked fine this long. Brass would be less bulky, like Cbody67 stated. There again, it looks like you'd really have to search to even notice it.
 
fwiw this is what the imperial dash gauge/light layout looked like ( i had been toying with the idea of swapping out my 300 convert's cluster to an imperial's )

20191024_210159 (2).jpg
 
What engine is this on?

On my 68 440 you can eliminate all of that mess. Put the dummy light back where it belongs and have the gauge in it's own port. The port that is circled was available, located on the passenger side below the heater hoses. On some RB's of different vintage there is a port on the dirvers side. I'd look around a little bit.

1670606435701.png
 
live4theking said:
What engine is this on?

On my 68 440 you can eliminate all of that mess. Put the dummy light back where it belongs and have the gauge in it's own port. The port that is circled was available, located on the passenger side below the heater hoses. On some RB's of different vintage there is a port on the dirvers side. I'd look around a little bit.
Click to expand...

You guys are great. Live4 - Its a 1970 440 with AC. Do you mean the bolt I circled which is on pass side comes out and is a port? If so, I'm not sure I have the room unless the sending units screws right in there without adapters. I didn't see anything on drivers side but there's no room on the drivers side mostly due to the A/C. Your idea is best but I might just look around for a smaller brass fitting as others have suggested.

I surprised myself. Its a VDO gauge. I guess I had some money back then. The sending unit is 1/2" 14NPT. Any way to test these sending units?

IMG_E4568.JPG
 
Wow. Well, Rock Auto didn't list the thread size and I'm using an aftermarket VDO gauge. Anyone know the thread size for the factory sending unit? VDO also has a 1/8" 27NPT too with same 250F 6-24V rating. Thanks
 
I recommend going to a local "good" auto parts store, if exists in your area, or hardware store, with sending units in hand, and piecing together your assembly at the store. This is something where you need to see the whole lot of available parts to achieve the best outcome.
 
Northcoast300h said:
Wow. Well, Rock Auto didn't list the thread size and I'm using an aftermarket VDO gauge. Anyone know the thread size for the factory sending unit? VDO also has a 1/8" 27NPT too with same 250F 6-24V rating. Thanks
Click to expand...
For my application, '75 440, rockauto lists standard motor products TS17 which is listed as 1/8-27 so you might be good!
 
live4theking said:
What engine is this on?

On my 68 440 you can eliminate all of that mess. Put the dummy light back where it belongs and have the gauge in it's own port. The port that is circled was available, located on the passenger side below the heater hoses. On some RB's of different vintage there is a port on the dirver's side.
Click to expand...
Get rid of all that piping. Totally unnecessary and doesn't give good temp readings for the aftermarket gage, since it's at a dead end. As @live4theking said, the aftermarket single-wire gage gets its own port.

Purple circle is OEM hot/cold temp switch (of course).

Yellow circle is location of the port for aftermarket sensor.

IMG_2303 - Copy.JPG
 
Northcoast300h said:
You guys are great. Live4 - Its a 1970 440 with AC. Do you mean the bolt I circled which is on pass side comes out and is a port? If so, I'm not sure I have the room unless the sending units screws right in there without adapters. I didn't see anything on drivers side but there's no room on the drivers side mostly due to the A/C. Your idea is best but I might just look around for a smaller brass fitting as others have suggested.

I surprised myself. Its a VDO gauge. I guess I had some money back then. The sending unit is 1/2" 14NPT. Any way to test these sending units?

View attachment 570939
Click to expand...
The factory gauge sending unit you have circled should read about 340 ohms at room temperature.
 
Trace 300 Hurst said:
Get rid of all that piping. Totally unnecessary and doesn't give good temp readings for the aftermarket gage, since it's at a dead end. As @live4theking said, the aftermarket single-wire gage gets its own port.

Purple circle is OEM hot/cold temp switch (of course).

Yellow circle is location of the port for aftermarket sensor.

View attachment 570948
Click to expand...
What he's saying here.
 
So I tested the OEM sender that was in there and its completed dead, which makes sense since its 52yrs old. Kind of odd that Chrysler would put the sender in without a gauge for it to be used.

Anyone know what the connector in the pic is called? I guess it just snaps on. I think I need to go with a 250F VDO sender since my aftermarket gauge is a 250F VDO
s-l1600.jpg
 
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