Getting my temp gauge to work

[putnam00]

Ok,
I put an lt1 in my truck. I've got a factory gauge cluster in my truck but the sending unit on my engine doesn't doesn't work with the gauge. What can I do to make it work or is it just easier to put an 80s temp gauge and sending unit in? I had to do that with the amp Meter because I'm not running the regulator anymore. Was told at one time I need a resistor?? If so what size?

[TBONE1964]

Originally Posted by putnam00

Ok,
I put an lt1 in my truck. I've got a factory gauge cluster in my truck but the sending unit on my engine doesn't doesn't work with the gauge. What can I do to make it work or is it just easier to put an 80s temp gauge and sending unit in? I had to do that with the amp Meter because I'm not running the regulator anymore. Was told at one time I need a resistor?? If so what size?

All of the early Chevy small block cylinder heads had a 1/2 NPT hole for the sending units. I believe (not100%) sure, your LT1 has a 3/8 NPT hole. Do you have a 1/2 NPT hole in the intake near the t-stat housing? You could install the temp sender there but it is not the best place for it.

You could drill and tap the 3/8 hole to the 1/2 in the drivers side cylinder head to accommodate the stock sending unit. Yes, the stock gauge does have a resistor on the back of it. I don't have my charts in front of my with the values.

I believe that someone may also make an adapter but I hear they are not very good and will cause the sending unit to stick out to far.

Keep us posted,
Tom

[FirstOwner69]

Below is a link to a recent thread where we discussed sensor options for engines requiring 3/8" NPT sensors, if that's what you need. A number of us have had the original 1/2" NPT sensors machined to 3/8" by board member brian mac. His contact info is in post 23.

http://67-72chevytrucks.com/vboard/s...d.php?t=627880

[putnam00]

There isn't a spot on the intake (fuel injected) and I really don't want to drill the head bigger I have a manual gauge but I don't want that as a permanent solution. The amp mater i put from behind and if no one knew what they were would think it's a factory one I might make the temp gauge the same way

[LockDoc]

-
I type too slow...

I put my sender in the intake by the water outlet and it reads wrong so I am going to have one turned down to fit in the head....

LockDoc

[TBONE1964]

Originally Posted by putnam00

There isn't a spot on the intake (fuel injected) and I really don't want to drill the head bigger I have a manual gauge but I don't want that as a permanent solution. The amp mater i put from behind and if no one knew what they were would think it's a factory one I might make the temp gauge the same way

What ever you decide, you need to make sure you keep the components matched, meaning the gauge has to match the sending unit with the correct resistor value. The gauge and the sending unit do not care what gauge cluster or engine they are in as long as they match.

By the way, I can as well as many people you will meet on this forum can spot an incorrect gauge in a 67-72 Chevy truck cluster from 100 yards away

Take care,
Tom

[putnam00]

So if I put the resistor from the 80s and arching sending unit would my factory gauge work? And I know people that knows these trucks would spot the non factory gauge just saying it looks factory and better than gauges hanging under the dash

[TBONE1964]

Originally Posted by putnam00

So if I put the resistor from the 80s and arching sending unit would my factory gauge work? And I know people that knows these trucks would spot the non factory gauge just saying it looks factory and better than gauges hanging under the dash

No, you need to make sure the gauge and the sending unit are from the same vehicle. If you don't wan't to drill and tap the 3/8 NPT hole to a 1/2 NPT hole then you are forced to use the later, smaller version of the sending unit which is not compatable with the factory gauge. You will have to use the temp gauge from the 80's vehicle also.


If it were me, I would keep my factory 67-72 temp gauge and have a the early style big sender machined down to fit the 3/8 NPT hole.

Hope this helps and yes you are correct, anything looks better than gauges hanging under the dash in my opinion.

[VDOG]

Originally Posted by putnam00

There isn't a spot on the intake (fuel injected) and I really don't want to drill the head bigger I have a manual gauge but I don't want that as a permanent solution.

I have the same engine minus the fuel injection. I first connected to the intake and got a wrong reading. I saw another on the driver side of the block.
Connected the temp gauge there and now it works.

[putnam00]

I think I'll just change it all don't want the headache if getting the sending unit turned down and risk it not working thanks for your time like I said I've already changed the amp meter

[putnam00]

It won't bother me as long as I have a temp gauge

[franken]

I went and looked at a cluster and the temp gauge has a rectangular white bit with a wire looped around it. To me, that's a resistor. My guess is that and the sender (heat actuated variable resistor) form a voltage divider and the gauge measures, or rather moves the needle based on the voltage across one of the resistances.

If the resistor on the gauge was replaced by a potentiometer of a somewhat larger resistance, it would allow tuning the gauge. I'd also guess the resistance of the needed pot is between 100-500 Ohms but I'd have to pull the resistor off and measure it...

It's just a theory but based on the parts involved, I'd bet money it's correct.

Pots can be bought for a buck or less for the board mount style. Maybe I could make up a few thousand and carve niche in a cottage industry. Of course there's probably no money in it, but...

As for the battery gauge (not Ammeter), the original took 12V from two points in the wiring harness (one near the battery, and one near the alternator) and the difference between the two moved the needle. So assuming a charged battery, the gauge saw about 13.4V-12.7V=0.7V. What all that means is, the battery gauge doesn't know if the vehicle has one type of alternator, another, or even a generator. It just moves a needle to indicate charge or discharge, or rather a difference in Voltage between two points.