Temp gauge problem - sending unit or gauge? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

shuttermutt · 12-17-2003, 11:09 PM

The needle on the temperature gauge in my 68 moves from zero to about 1/5 of the way up when fully warmed up. Needless to say, this isn't normal. I'm just wondering which I should tackle first, the sending unit or the gauge itself. Anybody ever have this problem?

bow-tie-bandit · 12-17-2003, 11:34 PM

I would check the thermostat also.

dinnut · 12-17-2003, 11:38 PM

has it always doen this? or is this abnormal... the first part of the gauge is about 80% of the degree scale and the other 80% of the gauge is the high temperatrues you dont want to be reading at

shuttermutt · 12-17-2003, 11:39 PM

Hmmm... if there was no thermostat (or it was stuck open) then the engine would eventually reach operating temperature, but it would take longer. On the other hand, if the thermostat was stuck closed then the engine would get hotter and faster. Am I missing something? It wouldn't be the first time!

shuttermutt · 12-17-2003, 11:40 PM

Quote:

Originally posted by dinnut
has it always doen this? or is this abnormal... the first part of the gauge is about 80% of the degree scale and the other 80% of the gauge is the high temperatrues you dont want to be reading at

It's done the same thing with both engines (the 307 and the 350). I've never seen the gauge go beyond the second "big tick" and towards what I'd consider normal (roughly straight up and down).

jhow66 · 12-18-2003, 02:30 AM

First mark past cold is approx. 180* Have a direct reading gauge also and it reads 180* when stock gauge is to 1st mark. When direct gauge goes up to around 200* (in traffic) stock gauges only goes a little past the 1st mark. This is normal range for stock gauge.

shuttermutt · 12-18-2003, 10:39 AM

This is what my gauge looks like when the truck is at full operating temperature. I've seen it creep just a little beyond this point, but not much. If I understand jhow66, this is approximately 180 degrees, right? If that's right, it sounds like my gauge is just fine and I just didn't know how to read it.

Huh... I coulda swore they went nearly straight up at full operating temperature. Oh well! One less part I've got to replace. Woohoo!

**JIMs70GMC** · 12-18-2003, 10:43 AM

Mine goes straight up and down w/ a 190 degree thermostat. Sounds like you might have a sender for an idiot light and not a sender for the gauge they are different.

shuttermutt · 12-18-2003, 10:48 AM

D'oh! I thought that was a little screwy. Hell, it's not like replacing the sending unit is expensive or time consuming. I'm gonna bite the bullet and make sure I've got the correct, working unit. Thanks JIMs70GMC!

tom hand · 12-18-2003, 12:05 PM

Quote:

Originally posted by shuttermutt
Hmmm... if there was no thermostat (or it was stuck open) then the engine would eventually reach operating temperature, but it would take longer. On the other hand, if the thermostat was stuck closed then the engine would get hotter and faster. Am I missing something? It wouldn't be the first time!

If your thermostat stuck open and your radiator is plenty big, it's never going to get over 150-160. First thing to do is see how hot you are running. You can get a kitchen thermometer at the grocery store for a couple of bucks. Let it sit and run with the cap off with the thermometer in the radiator...in about 20 minutes you will know what you have.

grebus1 · 12-18-2003, 01:48 PM

I have experienced both sides of this issue. My gauge used to read at second mark at normal temp. Then the sending unit crapped out. I have replaced it with 3 different senders and they all read at different part of the gauge at normal temp. The current one I ordered from Lectric Limited, who claimed it was calibrated correctly. The normal range is now straight up, but the gauge goes up almost all the way to hot before the thermostat opens. It is not a comforting sight! What gives? Does anyone sell a matched sender/gauge?

**JIMs70GMC** · 12-18-2003, 01:54 PM

grebus1 mine does the same thing what I think it is, is more fo a coolant flow problem near the sending unit. and the thermostat is open but it (cooler water) take's time to purge out all the hot water. or the the hot water takes awhile to get to the thermostat. Mine does it in the summer and winter, and even after replacing the thermostat.

shuttermutt · 12-18-2003, 02:48 PM

Well, now I'm as confused as ever. Should the needle be straight up when at "normal" operating temperature? Is that the goal?

**JIMs70GMC** · 12-18-2003, 05:26 PM

Yep! At least mine is just every now and then it goes past then comes back to the middle, usually when I first start it each day.

**Classic Heartbeat** · 12-18-2003, 05:36 PM

shuttermutt, I have had several trucks over the years and all of the gauges have read what your gauge is reading now. Yours may be slightly cooler. I run 180 degree thourmustats and the needles rise just a little above the first tick. It looks to me like yours is reading normaly. WES www.ClassicHeartbeat.com

shuttermutt · 12-18-2003, 05:45 PM

Thanks WES (and thanks to everyone else, too)! I think that I'm going to leave well enough alone for the time being. I may go ahead and stick a thermometer in there when I get a chance and verify that she's not running too hot.

BLACK AND BLUE 67-72 · 12-18-2003, 10:55 PM

Your reading is correct shuttermutt, that's usually where mine runs with a 180* degree thermostat, in all of my trucks.

lazybra1n · 06-07-2007, 03:15 PM

I just got my '70 running w/ an LS1. I used a VDO sending unit on the rear of the passenger side head, via a reccomendation from another online source, and a 160* thermostat. After about 5-10 minutes it runs the guage up to the top of the normal range, and would keep going if I didnt shut it off. The top, bottom & heater hoses are hot but theres no circulation in the radiator and its cold to the touch. What is the temp range for the stock guage? Am I not letting it get warm enought to open the therm. Is it possible that the sending unit is for an idiot light and not a gauge,or that it's not running long enough to open the therm even though it's creeping uncomfortably close to the "H"? To me it seems like the water pump is not pumping- but is that possible w/ the motor running? Theres no leaks and theres only 30,000 on the motor so I'm assuming the pump is still good... Any ideas?

JHART · 06-07-2007, 05:19 PM

Check this thread here. I posted a few picks of my temp gauge in here. If yours looks like this your good to go.

http://67-72chevytrucks.com/vboard/s...d.php?t=235946

12-17-2003, 11:09 PM	#1
shuttermutt Don't say "Oops!", Doctor Join Date: Nov 2003 Location: Houston, TX Posts: 677	Temp gauge problem - sending unit or gauge? The needle on the temperature gauge in my 68 moves from zero to about 1/5 of the way up when fully warmed up. Needless to say, this isn't normal. I'm just wondering which I should tackle first, the sending unit or the gauge itself. Anybody ever have this problem? __________________ 'Mutt 1968 CST LWB: R.I.P. 1967 Chevelle: TPI 454 beast 1967 C10 SWB: Claimed when Bumpster didn't put it on his list

12-17-2003, 11:34 PM	#2
bow-tie-bandit Live life and be happy. Join Date: May 2003 Location: Spokane,Washington Posts: 266	I would check the thermostat also. __________________

12-17-2003, 11:38 PM	#3
dinnut Registered User Join Date: Apr 2003 Location: missouri city, tx Posts: 4,486	has it always doen this? or is this abnormal... the first part of the gauge is about 80% of the degree scale and the other 80% of the gauge is the high temperatrues you dont want to be reading at __________________ 70 longbed 496/th400/Ford 9"

12-17-2003, 11:39 PM	#4
shuttermutt Don't say "Oops!", Doctor Join Date: Nov 2003 Location: Houston, TX Posts: 677	Hmmm... if there was no thermostat (or it was stuck open) then the engine would eventually reach operating temperature, but it would take longer. On the other hand, if the thermostat was stuck closed then the engine would get hotter and faster. Am I missing something? It wouldn't be the first time! __________________ 'Mutt 1968 CST LWB: R.I.P. 1967 Chevelle: TPI 454 beast 1967 C10 SWB: Claimed when Bumpster didn't put it on his list

12-18-2003, 02:30 AM	#6
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	First mark past cold is approx. 180* Have a direct reading gauge also and it reads 180* when stock gauge is to 1st mark. When direct gauge goes up to around 200* (in traffic) stock gauges only goes a little past the 1st mark. This is normal range for stock gauge. __________________ 56 Chevy Bel-Air 2dr. HT (purchased new) 71 Chevy Cheyenne SWB PU (502HO) 65 GMC short bed step--work in progress and my gofer

12-18-2003, 10:39 AM	#7
shuttermutt Don't say "Oops!", Doctor Join Date: Nov 2003 Location: Houston, TX Posts: 677	This is what my gauge looks like when the truck is at full operating temperature. I've seen it creep just a little beyond this point, but not much. If I understand jhow66, this is approximately 180 degrees, right? If that's right, it sounds like my gauge is just fine and I just didn't know how to read it. Huh... I coulda swore they went nearly straight up at full operating temperature. Oh well! One less part I've got to replace. Woohoo! __________________ 'Mutt 1968 CST LWB: R.I.P. 1967 Chevelle: TPI 454 beast 1967 C10 SWB: Claimed when Bumpster didn't put it on his list

12-18-2003, 10:43 AM	#8
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	Mine goes straight up and down w/ a 190 degree thermostat. Sounds like you might have a sender for an idiot light and not a sender for the gauge they are different. __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

12-18-2003, 10:48 AM	#9
shuttermutt Don't say "Oops!", Doctor Join Date: Nov 2003 Location: Houston, TX Posts: 677	D'oh! I thought that was a little screwy. Hell, it's not like replacing the sending unit is expensive or time consuming. I'm gonna bite the bullet and make sure I've got the correct, working unit. Thanks JIMs70GMC! __________________ 'Mutt 1968 CST LWB: R.I.P. 1967 Chevelle: TPI 454 beast 1967 C10 SWB: Claimed when Bumpster didn't put it on his list

12-18-2003, 01:48 PM	#11
grebus1 Registered User Join Date: Feb 2000 Location: Edmonds, WA Posts: 322	I have experienced both sides of this issue. My gauge used to read at second mark at normal temp. Then the sending unit crapped out. I have replaced it with 3 different senders and they all read at different part of the gauge at normal temp. The current one I ordered from Lectric Limited, who claimed it was calibrated correctly. The normal range is now straight up, but the gauge goes up almost all the way to hot before the thermostat opens. It is not a comforting sight! What gives? Does anyone sell a matched sender/gauge? __________________ '72 Chevy Suburban Custom Deluxe 10, 402/TH400

12-18-2003, 01:54 PM	#12
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	grebus1 mine does the same thing what I think it is, is more fo a coolant flow problem near the sending unit. and the thermostat is open but it (cooler water) take's time to purge out all the hot water. or the the hot water takes awhile to get to the thermostat. Mine does it in the summer and winter, and even after replacing the thermostat. __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

12-18-2003, 02:48 PM	#13
shuttermutt Don't say "Oops!", Doctor Join Date: Nov 2003 Location: Houston, TX Posts: 677	Well, now I'm as confused as ever. Should the needle be straight up when at "normal" operating temperature? Is that the goal? __________________ 'Mutt 1968 CST LWB: R.I.P. 1967 Chevelle: TPI 454 beast 1967 C10 SWB: Claimed when Bumpster didn't put it on his list

12-18-2003, 05:26 PM	#14
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	Yep! At least mine is just every now and then it goes past then comes back to the middle, usually when I first start it each day. __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

12-18-2003, 05:36 PM	#15
Classic Heartbeat Project Junkie! Fishing Poor!! Join Date: Dec 1999 Location: Olympia,Wa. 98512 Posts: 10,766	shuttermutt, I have had several trucks over the years and all of the gauges have read what your gauge is reading now. Yours may be slightly cooler. I run 180 degree thourmustats and the needles rise just a little above the first tick. It looks to me like yours is reading normaly. WES www.ClassicHeartbeat.com __________________ On-line catolog Classic Heartbeat Pickup Parts WEHEPP@comcast.net Call us Toll Free (888) 338-2502 Like Us on Facebook No appointment necessary. 72 BB Chevy Custom Deluxe / Custom Camper 67 I-6 (Soon to be 5.7 LS1) Panel 68 BB Chevy Short Bed 72 6.0 LQ9 Short Bed Chevy 4X4 Olympia's fastest growing truck parts supplier. Olympia's home for Wayward Chevys

12-18-2003, 05:45 PM	#16
shuttermutt Don't say "Oops!", Doctor Join Date: Nov 2003 Location: Houston, TX Posts: 677	Thanks WES (and thanks to everyone else, too)! I think that I'm going to leave well enough alone for the time being. I may go ahead and stick a thermometer in there when I get a chance and verify that she's not running too hot. __________________ 'Mutt 1968 CST LWB: R.I.P. 1967 Chevelle: TPI 454 beast 1967 C10 SWB: Claimed when Bumpster didn't put it on his list

12-18-2003, 10:55 PM	#17
BLACK AND BLUE 67-72 Firefighter Join Date: Feb 2001 Location: Yellville, Ar, USA Posts: 1,943	Your reading is correct shuttermutt, that's usually where mine runs with a 180* degree thermostat, in all of my trucks. __________________ '72 Chevy SWB 350 Auto '67 GMC LWB 350 4 speed '70 Chevy 4x4 Stepside 350 Auto Yellville, Ar. USA



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06-07-2007, 03:15 PM	#18
lazybra1n Registered User Join Date: Mar 2007 Location: Modesto CA Posts: 29	Re: Temp gauge problem - sending unit or gauge? I just got my '70 running w/ an LS1. I used a VDO sending unit on the rear of the passenger side head, via a reccomendation from another online source, and a 160* thermostat. After about 5-10 minutes it runs the guage up to the top of the normal range, and would keep going if I didnt shut it off. The top, bottom & heater hoses are hot but theres no circulation in the radiator and its cold to the touch. What is the temp range for the stock guage? Am I not letting it get warm enought to open the therm. Is it possible that the sending unit is for an idiot light and not a gauge,or that it's not running long enough to open the therm even though it's creeping uncomfortably close to the "H"? To me it seems like the water pump is not pumping- but is that possible w/ the motor running? Theres no leaks and theres only 30,000 on the motor so I'm assuming the pump is still good... Any ideas?

06-07-2007, 05:19 PM	#19
JHART 1972 Shorty Owner Join Date: Feb 2007 Location: Stationed in Cali , born and raised in PHX Arizona. Posts: 796	Re: Temp gauge problem - sending unit or gauge? Check this thread here. I posted a few picks of my temp gauge in here. If yours looks like this your good to go. http://67-72chevytrucks.com/vboard/s...d.php?t=235946 __________________ 1972 Chevy Shorty C-10- Project In Work http://67-72chevytrucks.com/gallery/...ATT1721941.jpg- New Project Last edited by JHART; 06-07-2007 at 05:19 PM.

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