Trying to match sending unit/gage ohms

[SoCal71K20]

I knew I should have payed more attention
during the auto electrical theory part.
Anyways,I know that original temp. sending
unit has resistance listed as 72-88 ohms@
220 degrees.I will use original type gage
with one wire hookup.I cannot use 72-88 ohm
sending unit because of head swap and I want
to keep it off of intake manifold if possible.I can get a newer style sending
unit thats listed as 138-156 ohms @220
degrees.Is there any way to match resistance
to gage?Use of resistor?Hope I didn't word
this too confusing.Thanks.

[robby]

I would like to know myself, I have a 307 with later model 305 heads and it has a smaller hole for the sender, I have it in the manifold but I don't like it.

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72 C-20 parts 70 C-10 lwb driver
69 C-10 lwb parts
72 K-5 Blazer-NEW!
Lamar,Missouri
Semper Fidelis

[Longhorn Man]

I doubt it.
You are trying to make a high resistance part work on a low resistance syatem. If it were the other way around, it would be easy.
you could always remove the head and have the machine shop hog it out. But that soundsa a little extreem to me.

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'69 G.M.C. 350/350. Trying to clean up the left over damage from the Dope-Smokin-Old-Man
I've been dubbed the Longhorn Freak/Fanatic/Expert, I just hope I can live up to it.
FINALLY got the HORNIAC...a '70 one ton Longhorn with a Pontiac 350/350 and lots of 'personality'. Check out The Longhorn Webite.
E-mail longhornmail@yahoo.com
My name is Andy...not Randy...I'm in Ohio...Not Illinois...close enough?
Columbus Ohio

[RodC]

You could try to put a resistor in Parallel with the sending unit to bring it down to the proper range, provided that the upper range of the sending unit minus the lower range of the sending unit is the same on the low resistance sending unit as the high resistance one.

Remember resistors in parallel will reduce the resistance, resistors in series are additive. Thus two 4ohm resisters in parallel = 2ohms

The average of the low resistance sending unit you mentioned is 80 ohms. The average of the high one is 147. In theory, a 20 ohm resistor in parallel with the 147 will give you 83 ohms. (20+147) / 2 = 83.5 Your best bet would be to use a variable resistor to set it at 220 degrees. Then check the sending unit at various temperatures to see if you can obtain a correlating resistance between the gauge and the sending unit.

OR…….

Or you could just find an adapter that would allow you to put your sending unit into your head. I know a lot of after-market gauges come with various adapters?


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Rod Childers
'71 C10 Stepside

[Mudder]

then how can we get our newer sending units to work with or old gauges? (gas gauge)

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67 stepside 4x4 Owensville MO mudder67@hotmail.com




[This message has been edited by Mudder67 (edited May 25, 2002).]

[RodC]

What is the Restiance range of the old Sending units? (Full - Empty)

What is the Resistance range of the New Sending Unit? (Full - Empty)

Check both of these out with an OHM meter or the spec sheet and let me know.

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Rod Childers
'71 C10 Stepside

[bigvinnie]

I'm running a tank from No Limit Engineering that came with a VDO sending unit that works fine with the stock fuel guage.... as I recall, the instructions for the sender said it was rated at 0-90 ohms... I just played with the length of the float rod to get it to read empty/full with the corresponding float level.

The VDO sender works great with the stock fuel guage...

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'72 short step, 350, 700R4, tilt, ps, pdb, a/c, lowered coils, etc., other work in progress... San Diego, CA
http://www.ixpres.com/vlusardi/chevtrk.htm