I am trying to fix my broken temperature gauge, and am going to start by installing a new sending unit. Is there benefits/drawbacks to the single prong vs. the two prong one. Which is better? does it matter. Thanks

70' 350/350 fyi.

 

Have you done the standard test?

 

Hi DW,
Even if Drizzle has done it, I'd like to know the temp sender test.
Regards,
Alan

 

Apologize for my ignorance, what is the standard test? I guess that means that I didnt do it. I will as soon as I know what it is. Help me out. Thanks.

 

The test is simply removing the sender wire and checking the gauge with the IGN on. Then, touching the sender wire to ground and seeing if it pegs the other way.

That will eliminate the gauge from the wiring and sender as a suspect.

There is no two prong sender for you. One prong only.

 

First. Thanks as always for all help.

Let me elaborate.

The guy I bought it from has a two prong sending unit in the car now. The temp gauge has not worked since I bought the car 2 months ago.
with the engine off, I can tap the gauge and get the needle to fall a little (to like nine 0' clock), then at ignition, it jumps to 100 degrees (so it is at least getting juice). But it never moves from there. I noticed that he had a two prong sending unit with just one wire hooked up to it (the green one). I figured if I grounded the other one, that it would work, so I did that this morning. drove for 10 min and it never moved. then I flipped the wires to see what happened. again nothing. from here, where would you go?

DB, are you saying that I should ground the green wire to see if it peggs the gauge. i will, but before I ground a wire that may be hot, i wanted to make sure that is what you are saying before I do that. Thanks.

 

The "2 prong" device in the right cylinder head is not a temp sender. It is the TCS switch which operates with the TCS solenoid on the carb. Go to lectriclimited.com to see the proper sending unit designation. Lots of places sell the 'wrong' sender for your car; LL sells the correct unit.

 

Yes as DB said with the key on remove the green wire at the sender and the gauge should peg towards cold.
Then ground the same green wire and the gauge should go to full hot.
This usually means your gauge, wiring and voltage to the gauge is in good shape.

Drizzle...are you working on the drivers side of the engine or as 7T1vette noted the passenger side?

 

The driver's side gets a single pronged sender for TEMP and the passenger head had a TCS sensor that most people remove. The previous owner put in the wrong one if it's in your driver's side head. Get a real sender for your year and your gauge will probably work just fine.

The sender wire is NOT HOT so you won't see sparks. The sender actually grounds that wire to the block so touching the wire to a ground will only do what the sender does but without any resistance.

 

thanks. Ya'll are great

 

just grounded that green wire and the gauge went haywire. I will order the sending unit tomorrow from zip! You have no idea how glad I am. I started with one working gauge (the tach), now all I have left to fix is speedometer/odometer, gas gauge, and clock.



---donnie

 

Hi Alan
Sorry didnt see your post until now.Its pretty easy and quick,just turn the ignition on and pull the wire off the sender and the gauge should peg towards cold....then ground the wire going to the sender and the gauge should peg towards hot.
The way I remember "which way" the needle should go is easy...its the opposite of the way I think it should be if a wire falls off or is knocked off a sender.It would be nice if when the wire accidentally falls off the temp gauge for instance the needle would go full HOT so you would be alerted that something is wrong,but its just the opposite it goes to COLD.Leaving you with the false sense that your engine is OK and just running cool.I had a customer that changed his anti-freeze,tuned the engine(knocked off the sender wire) and didnt get enough coolant back in the engine.He went for a road test overheated and ruined the engine thinking that the engine was running cool because of the flush and new anti-freeze.
The oil pressure is the same,wire falls off and guess what you have GREAT oil pressure...NOT.
The gas gauge is the same wire falls off and you have a FULL tank.That one got me one time and I ran out of gas.
Moral to the story guys is if your gauges go to the good or safe side and stay there "TAKE NOTICE" a broken or disconnected sender wire can force your gauges to LIE to you.