Factory Temp Gauge reading?

[custom10nut]

What is the Factory Temp gauge normally read? I normally run just past the half but today I’m near the red line. I’ve been having issues with it reading correctly, so I’m thinking I need to replace the wire. I put a new sensor in last year and it was good, but I think the connector on the end of the wire is not keeping enough tension to give an accurate reading.
Any thoughts or tips?

[RustyPile]

In a properly operating engine operating temperature gauge circuit, where the gauge needle "normally reads" is dependent on the temperature rating of the thermostat which controls the operating temperature of the coolant/engine.. A 160 thermostat will indicate a totally different reading from a 180 thermostat, as well as a 190 or even a 195.. So to answer your question, what the gauge "normally reads" could be anything.. If it were me, before I start guessing at the cause and throwing parts at it, I'd be looking at the actual temperature of the engine, in particular, making sure the engine isn't overheating.. Parts swapping is not a proper diagnostic procedure..

[custom10nut]

Yeah, It just boggles my mind. Much of my issue is my truck sits a lot and these little things crop up when I start driving her again. I haven’t changed anything that would make her run hotter. one day I’ll get in and everything works fine then another the gauge will be pegged. Again, this is why I’m leaning toward the connector

[Steeveedee]

I changed out the factory sensor when this happened but ended up with an aftermarket gauge. Long time ago, before I joined here, I think. Based on what I've read here, it's potentially a bad connection either in the printed circuit or the gauge, but I never got around to pulling all that apart to check.

[72c20customcamper]

If it was a bad connection at the sensor it would read lower. They work on a ground principal. The warmer the engine the higher the grounding. Just like the fuel sender .

[MySons68C20]

Mine floats between middle and the lower edge of the "hot" zone. I have a 180 deg thermostat and a new alum radiator and can watch the temp climb and stat open on the gauge within those ranges. My guess is the diff between those two swings is only 20 deg.....I'm going to shoot it with the laser one of these days to see what it really is.

[custom10nut]

Originally Posted by MySons68C20

Mine floats between middle and the lower edge of the "hot" zone. I have a 180 deg thermostat and a new alum radiator. and can watch the temp climb and stat open on the gauge within those ranges. My guess is the diff between those two swings is only 20 deg.....I'm going to shoot it with the laser one of these days to see what it really is.

That’s where mine is too, so maybe I’m just being paranoid. I’m gonna watch it this week, an maybe try a 160 thermostat, just to see what it does.

[WorkinLonghorn]

Just for comparison, I have the standard 195° thermostat and I can drive around all day and the gauge never gets past about the width of two needles past the cold mark. On a hot summer day hauling some weight on a slow hilly road it may get past the 1/2 mark and even reach about half way between straight up and the hot line.

[custom10nut]

Good observation. Summer here in S.C. the temp stays about 95+ so like i# aid before, I didn’t drive it at all this winter so probably forgot what it runs on a normal day. I’m finally moving up to the mountains of Tennessee this month, so I won’t be driving on the Surface of the Sun anymore. Once I get settled I’ll PM the members in the immediate area to finally meet, face to face.

[rpmerf]

70 C20 350, 195* thermostat.
Usually sits around half way up the gauge. It does go up to about 3/4 of the gauge sometimes, but never outside the operating range. I think the headers throw off the sender a bit. I rigged up a temperature sensor in the upper radiator hose. It would be rock solid while the factory one is moving between half and 3/4. I've measured the temperature on the back of the sender and it would read 230* while the heads, and intake intake at the water ports, and thermostat housing are reading right around 195*.

How I rigged the sensor in the upper intake hose. I had a temperature sensor from a 80's dodge. I had a temp gauge that worked with that sensor. I took a piece of exhaust pipe, drilled a hole in it, welded on a nut over the hole, a bolt on the back side, and bumps on each end so it wouldn't blow off. I used the bolt to ground it to the body. I cut the upper hose and installed it in the center. Ran a wire from the sensor to the gauge. It's rigged, but it gives me a second data point. I always drill a bleed hole in my thermostats, so it would still read before the thermostat opens.

[custom10nut]

See, mine started “running a little hotter” when my son replaced the old radiator and did a system flush, the only one its had since I rebuilt the engine. I think everything just got all unplugged and cleaned out and Quite possibly, it’s reading normal and I’m making an issue out of nothing. One thing I have noticed is that the coolant is not boiling, so it’s not getting TOO hot.

[rockyrivermark]

Mine only reads a 1/4 off of cold when fully warmed up
Best and easiest thing to do is get an IR gun. They are about $20.
Get to operating temp, take a reading and then you know what the gauge is at.

[demian5]

Buy a cheap non contact thermometer gun and take readings. I have a gauge in a 60 with the right sender in the head. The gauge goes full hot, then the t stat opens and it goes to the middle. The t stat housing, head and radiator may read 180 degrees (thats the thermostat in it). I installed a mechanical gauge as well and it may get up to 180 tops (when the factory gauge is pegged for that moment)...


My 1970 reads about 1/4 on the factory gauge at the most and it is at about 185 measured at the tstat, radiator and head (again, that's the thermostat in the motor).

Piece of mind then you know what your trucks gauge character is.

[custom10nut]

Well, I pretty much narrowed it down. The water temp was at 180 deg after running for about 45 mins, the t-stat is new, and the wire connector iss new.
Someone mentioned the connections on the printed circuit.
I think that may be the issue.
Due to the amount of moisture under the dash (from my leaky windshield seal) and the propensity to build corrosion, that’s where it’s pointing too..
I don’t have the time this week to tear the dash apart, to clean the contacts, but at last I know it’s cooling properly

[demian5]

Originally Posted by custom10nut

Well, I pretty much narrowed it down. The water temp was at 180 deg after running for about 45 mins, the t-stat is new, and the wire connector iss new.
Someone mentioned the connections on the printed circuit.
I think that may be the issue.
Due to the amount of moisture under the dash (from my leaky windshield seal) and the propensity to build corrosion, that’s where it’s pointing too..
I don’t have the time this week to tear the dash apart, to clean the contacts, but at last I know it’s cooling properly

You do know that the gauges have replaceable resistors right?

Search the forum for that info.

[custom10nut]

I didn’t know that, and I’ll look it up. Thanks. .

[demian5]

Originally Posted by custom10nut

I didn’t know that, and I’ll look it up. Thanks. .

http://67-72chevytrucks.com/vboard/s...d.php?t=689065

[custom10nut]

Well, after talking to a Good Friend of mine, he told me to trace the wire and look for any weak spots/breaks. I did and found the connector on the firewall was loose, I disconnected it put some dielectric grease on the contacts, and VIOLA! the gauge is working again.

[gator2511]

I got tired of fighting the printed circuit board so I just yanked it out and hard wired the wires. No problem since then.

[garyd1961]

19

Originally Posted by rockyrivermark

Mine only reads a 1/4 off of cold when fully warmed up
Best and easiest thing to do is get an IR gun. They are about $20.
Get to operating temp, take a reading and then you know what the gauge is at.

That's where mine runs and all the ones I remember seeing back in the day ran right around the 1/4 mark. If your gauge is floating around you may have a problem.. Mine did that before I added a bypass hose from the intake to the water pump.

[dmjlambert]

Mine goes from cold up to this position, slowly over the first 5 minutes or so that the engine is running.

Once it arrives at that position it stays steady regardless of 32 degrees or 115 degrees outside. I have a 180 degree thermostat.
If I park the truck and come back 10 or 20 minutes later and start it, the gauge begins at 1/2 with the needle straight up, and within about 15 seconds goes down to the pictured reading.

[aerotest]

Exactly how mine functions

[garyd1961]

Originally Posted by dmjlambert

Mine goes from cold up to this position, slowly over the first 5 minutes or so that the engine is running.
Attachment 1909920
Once it arrives at that position it stays steady regardless of 32 degrees or 115 degrees outside. I have a 180 degree thermostat.
If I park the truck and come back 10 or 20 minutes later and start it, the gauge begins at 1/2 with the needle straight up, and within about 15 seconds goes down to the pictured reading.

Are you running a 195 thermostat? That's where mine runs wirh a 195, I'm running a 180 now and the gauge runs a little closer to the 1/4 mark.

[mr.precision]

Originally Posted by WorkinLonghorn

Just for comparison, I have the standard 195° thermostat and I can drive around all day and the gauge never gets past about the width of two needles past the cold mark. On a hot summer day hauling some weight on a slow hilly road it may get past the 1/2 mark and even reach about half way between straight up and the hot line.

Exactly the same on my '67. 283, new radiator, 180* thermostat. Phoenix weather....up to 115 in the summertime (not that I drive it during that time of year.. much).

[brown7373]

I live in south Florida and run my A/C. Mine is identical to dmjlambert. And the thermostat has nothing to do with the operating temperature. The thermostat controls WHEN (at what temperature) it opens. There is no difference between an open 160 or a 195. They both flow the coolant the same. Once either is open, the temperature is determined by the efficiency of the cooling system. And is the engine making more than normal heat.

If you gauge is near hot, then either you are in fact over heating or the gauge or sending unit is not accurate. Check it with a known good gauge, or use a temperature gun.