temp gauge

[mehoff400]

i changed out my 230 about a year ago for a 250. when doing this ever since then the temp gauge doesn't work correctly. everything i have checked with a temp gun is telling me the engine is running around 180. driving it around it runs normal and i can put my hand on valve cover. yes it is a 12bolt valve cover but its not even a little warm. when warming up the gauge slowly moves up and goes to normal. if i rev the engine it seems like the gauge moves up as i rev the truck up. like the rpms are making the gauge move i know seems weird. i have changed everything from thermostat, temp sensor, and the actual gauge itself with no change.

any suggestions?

[chevylookin]

What is a 12 bolt valve cover? My ammeter will flicker all the time but no other gauges should. You mean it revs like a tach gauge?

[mehoff400]

12bolt is the brand of the valve cover.

i guess i could of explained what it does with the RPMs a little better. if i let it idle up to temp the gauge moves as it should. once i give the truck some gas and hold it, it seems the gauge moves almost at the rate the rpms move up. if i give it gas the temp gauge will move up. if i let it idle again the gauge wont move up until i give it more gas. it will keep doing this until the gauge is pegged.

[chevylookin]

Sounds like you better call the priest over. I would try to replace the sender wire or trace it for a an open short. Is your instrument panel all screwed in and grounded to the dash well? The only other long shots i can think of is ignition circuit problems. Are you still running points? I dont know how they could interfere with the temp gauge but check your condenser. Have you added a tach somewhere?

[mehoff400]

You might be on to something.. I did add a tach when I did this swap. I will need to look at the wiring for it

[Palf70Step]

Did you run a ground strap from the cylinder head to the firewall? Sounds like your demon might be a grounding issue. Either that or the sensor in the 250 is bad or doesn't match the ohms for the gauge.

[mehoff400]

removing the power and disconnecting the ground from the tach not seeing any changes in temp gauge.

looking online the part numbers are the same for the 230 i had and the 69 nova 250 i currently have for the temp sensor.

its possible the cheap temp sensor is not correct at my local orilleys as i have gotten incorrect parts from them before. i just ordered a acdelco temp sensor from rock auto maybe that will help.

[chevylookin]

Have you done a resistance test on that sensor? Here is a good tutorial on how to do it as long as you have your multimeter: https://www.youtube.com/watch?v=wFHWpgHMAvY
So, you are running your factory temp gauge, correct? You still have the factory terminal connector which prevents you from getting the wires mixed up for knuckleheads like me, right? Palf70step is right. You want to ensure that you eliminate all that pesky engine static by grounding the engine to the frame if necessary because it is the power of gremlins.

[jayoldschool]

Perhaps the new engine has a simple sender for a light instead of the correct sender for a gauge.

[65 C20]

Originally Posted by jayoldschool

Perhaps the new engine has a simple sender for a light instead of the correct sender for a gauge.

I was thinking the same thing.
Happened with a friend of mine with his '67.
Had the wrong type of sender.

[The Rocknrod]

The correct one: https://www.lectriclimited.com/elect...ing-unit-86912
Some info: http://67-72chevytrucks.com/vboard/s...d.php?t=587190
Found in the FAQ section: http://67-72chevytrucks.com/vboard/s...d.php?t=646002

[mehoff400]

mmmmmhhh!! lots of good info guys! thanks for the help! i am going to clean up my ground on the block and see what that does. i have a temp sensor coming in so i will see what that will do before ordering the one listed.

looks like the gm 1513321 cross references acdelco 1852 and that is the one i got on order currently should be here thursday.

[mehoff400]

after doing some reshearch and looking up the part number i got from oriellys WT203 looks like it is for the light. and WT203P is for a gauge of course that one is cheaper but you have to order that one so i got the WT203. the one coming in from what i can tell will fix this issue i am having.

thanks again for the help guys

worst thing is i caused my own problem my old thermostat sensor was working just fine i just was replacing everything bolt on for the new engine.

[jayoldschool]

Glad to help, happy it's an easy fix.

[The Rocknrod]

It would be interesting to find out if this part number were indeed a good one. keep us posted on the actual temps and gauge readings if possible. Everyone would like to know either way.

[shp4man]

The parts they sell now aren't accurate with the temp guages in our trucks. I put a potentiometer in the sender wire, shot the tstat housing with an Infrared temp sensor after the truck warmed up to the thermostat opening temp, in my case 195 degrees, then dialed in the guage to the center with the potentiometer.
Turned out to be about 13 ohms. Your results may vary.

[mehoff400]

will update when i get the new thermostat sensor in

[mehoff400]

well..... seems like the one i got from rock auto redeemed the same results incorrect reading. so either it is the incorrect sensor still or i have something going on with electrical still.

at this point i think i would need to test the new sensor to get an ohms reading

[The Rocknrod]

https://www.lectriclimited.com/faq/
The correct one: https://www.lectriclimited.com/elect...ing-unit-86912
Some info: http://67-72chevytrucks.com/vboard/s...d.php?t=587190
Found in the FAQ section: http://67-72chevytrucks.com/vboard/s...d.php?t=646002

[PGSigns]

When it comes to temp and oil pressure I want a good mechanical gauge. I have always added them. The temp gauge in our trucks just never gave me the accuracy I wanted.
Jimmy