Temperature Sending Unit - The 1947 - Present Chevrolet & GMC Truck Message Board Network

70LonghornCST · 05-03-2009, 10:17 PM

I recently purchased a new temperature sending unit and it was too big. I need one that has the flat head so I can connect my harness wire to it. My old one only had threads and a small nut. I don't want to cut the wire and crimp on a circular terminal. I want it to look stock with the plastic end that slips over the flat head. The one I purchased was advertised on eBay as "Temperature Sender 1967 68 69 70 71 72 Chevy/GMC Truck"

But when I pulled my old one out, it was much smaller. The new one required a 15/16" socket, while the old required a 3/4" socket. I pulled it from the side of the block on the driver side.

The engine is a replacement 350 crate engine from a GM dealer.

Help! Are there different sized temp sending units for a 350?

70LonghornCST · 05-04-2009, 01:28 AM

ttt

texanidiot25 · 05-04-2009, 01:44 AM

Photos of the one you have on hand, and the one you want?

The one I got from Napa? was about he size of a half dollar coin, with a nail-head-like terminal. I just cut the plastic cover off the female end of regular connector and slid it over the end. Works for me, just a driver.

A.P. · 05-04-2009, 01:48 AM

Scroll down to page 98 or 99.
http://www.scribd.com/full/5722345?a...jcbazlklxtunnw

monte0185 · 05-04-2009, 04:33 PM

My guess is you either have a later model set of heads that requires you to have a 3/8NPT sensor or you have an aftermarket sensor with an adaptor. The correct size is a 1/2npt thread size but if you have late model heads you will need to turn the sensor down on a lathe and rethread it or find a sensor that will work with your gauge. I have yet to find one to work with my gauge.

texanidiot25 · 05-04-2009, 04:43 PM

Well what does the wrong sensor do to your gauge?

With my older small block, we just ordered one that was designated for the truck. Dunno if the connector is proper, but it works.

monte0185 · 05-04-2009, 04:49 PM

The new 3/8npt sensor will not work with the 67-72 gauge. It will read hot when its not. The ohms are different for later model gauges than ours. What are the casting #'s on your heads. I just went through all this with mine. Im running a set of 99 model vortec heads. I had to have someone turn my sensor down and rethread it. I havent had a chance to try it out yet though.

JimKshortstep4x4 · 05-04-2009, 08:10 PM

I had the same issue with the newer heads having smaller threads. I ended up drilling and tapping the head 1/2 NPT and using the sensor for our trucks. I had gone to NAPA and they have the ohm listing for all of the sending units but no luck on having the correct ohms in a smaller thread version of the sensors.

I believe the range needed in order for the sending unit to work with the truck gauges is in the 80 to 900 ohm range, (80 ohms being hot and 900 being cold).

Jim

texanidiot25 · 05-04-2009, 10:03 PM

Quote:

Originally Posted by monte0185

The new 3/8npt sensor will not work with the 67-72 gauge. It will read hot when its not. The ohms are different for later model gauges than ours. What are the casting #'s on your heads. I just went through all this with mine. Im running a set of 99 model vortec heads. I had to have someone turn my sensor down and rethread it. I havent had a chance to try it out yet though.

Wouldn't an easier mod be tossing on a resister in series to correct for the difference in Ohms? Similar to the changes some make to correct for their fuel guages with different sending units.

I would imagine that being far easier/cheaper than having to have the sensors machined.

monte0185 · 05-05-2009, 08:27 AM

Quote:

Originally Posted by texanidiot25

Wouldn't an easier mod be tossing on a resister in series to correct for the difference in Ohms? Similar to the changes some make to correct for their fuel guages with different sending units.

I would imagine that being far easier/cheaper than having to have the sensors machined.

If it could be done I would completely be up for that. I think the problem with that is the newer sensors are backwards from the older ones. I dont think you can correct this with an inline resistor. I could however be wrong though.

sleepertruck72 · 05-05-2009, 11:14 AM

I put my temp sending unit on my intake manifold and it works just fine. Is that an option ? My engine is a 350HO crate engine with Vortec Heads. I had to crimp on a not so stock looking terminal, but I'm sure you can find a stock looking one or somehow take the black plastic cover to the old one and get it to cover up the ugly terminal ?

texanidiot25 · 05-05-2009, 04:28 PM

The head is a more reliable point to put the sensor. Up top, given if you had a coolant leak, your sensor would no longer be reading the coolant temp, just the hot air. Which could give a false reading saying your cool, when your over heating.

70LonghornCST · 05-05-2009, 08:56 PM

Thanks for all of the replies. I will 1st double check to see if there is a second port option for a larger sized sensor. If not, I will try some of the suggestions offered. I wonder if a different car maker has an approptiate sized sensor that will work? I know Mopar has a smaller sized sensor, but I am not sure about the OHMS.

powell72 · 05-05-2009, 09:23 PM

I also have the later heads and I have my sensor in the intake, works just fine.

*highperf4x4* · 05-05-2009, 09:24 PM

I plugged my head and moved the sending unit to the intake manifold.

berencam · 05-05-2009, 10:16 PM

try a sending unit for a set of 90s era heads, mine is the small type like your talking about. i ended up using an aftermarket gauge and mounting in the original location.

70LonghornCST · 05-06-2009, 01:44 AM

Well, I don't have a port for a 1/2 anywhere else on the block, and the stock manifold does not have a plug anywhere I can see.

However, I found this adaptor on ebay (220388003191). What do you think?
It shows as 3/8" NPT male to 1/2" female.

youhaveamonkey · 05-06-2009, 02:25 AM

I have a 350 and mine is tapped for 1/2 NPT. I would be VERY careful with an adapter like that. A brass adapter can act as a heat sink and shift the position of the sensor. The sensor was engineered to be in a specific place and it needs to be there otherwise it will give you inaccurate readings. Not that it is a a bad idea.
Mechanically you could find a brass bushing that would locate the sensor in approximately the correct place.This would be all threads on the outside and inside. Should be able to get one at any plumbing supply house. But make sure it is a bushing NOT an adaptor. then you have the other problem. the output of the sensor. Don't know what to tell you about that. Best of luck. Just my .02.

arrrgh, I just re-read your post. I am sorry. Never mind what I just said about the bushing. Just be careful with the adapter.

brian mac · 05-06-2009, 09:26 AM

I can machine the stock style sending unit to fit head holes that are 3/8 pipe. Price is 25.00 shipped. This includes a new sending unit that has been modified. I sent one to member monte0185 but he has not installed it yet. PM me if you are interested or have questions.

monte0185 · 05-06-2009, 09:49 AM

Quote:

Originally Posted by brian mac

I can machine the stock style sending unit to fit head holes that are 3/8 pipe. Price is 25.00 shipped. This includes a new sending unit that has been modified. I sent one to member monte0185 but he has not installed it yet. PM me if you are interested or have questions.

Looks fantastic by the way!! I was going to install it yesterday while we had a break in the rain but had to mow the yard instead!! Darn house chores anyway.

This is the route I suggest. I have talked to a couple people who have drilled their head out to fit but theres not alot of meat there for new threads At least it was that way on my vortec heads so if not done right you can ruin the head easily.

70LonghornCST · 05-06-2009, 05:43 PM

Quote:

Originally Posted by brian mac

I can machine the stock style sending unit to fit head holes that are 3/8 pipe. Price is 25.00 shipped. This includes a new sending unit that has been modified. I sent one to member monte0185 but he has not installed it yet. PM me if you are interested or have questions.

Awsome!
PM sent.

hot trux · 06-03-2013, 12:17 PM

Quote:

Originally Posted by brian mac

I can machine the stock style sending unit to fit head holes that are 3/8 pipe. Price is 25.00 shipped. This includes a new sending unit that has been modified. I sent one to member monte0185 but he has not installed it yet. PM me if you are interested or have questions.

Pm sent
Posted via Mobile Device

Lead Sleader · 08-04-2014, 12:35 AM

Brian Mac posted that he could turn down and rethread a dual temp sender. I would like to see if he is still around and can do this for me. It is the sender for the hot and cold lights. It is in my 65 chevy impala with a 350 and late model heads and a TPI. He was the only one that had a very good idea. I am also working on a 72 Chevy pickup. Any help ....

**FirstOwner69** · 08-04-2014, 11:44 AM

Quote:

Originally Posted by Lead Sleader

Brian Mac posted that he could turn down and rethread a dual temp sender. I would like to see if he is still around and can do this for me. It is the sender for the hot and cold lights. It is in my 65 chevy impala with a 350 and late model heads and a TPI. He was the only one that had a very good idea. I am also working on a 72 Chevy pickup. Any help ....

See post 23 in this thread http://67-72chevytrucks.com/vboard/s...d.php?t=627880 for Brian Mac's contact info. You can also send him a PM. However, his last forum activity was July 18, so it may take a few days for a response.

Welcome to the forum!!

74baggedbug · 08-04-2014, 12:16 PM

I had mine machined down cause I'm running newer heads. That's the only way it will work so you can use the factory gauge cluster ..

05-03-2009, 10:17 PM	#1
70LonghornCST Moderator Join Date: Jun 2008 Location: Modesto, CA Posts: 5,775	Temperature Sending Unit I recently purchased a new temperature sending unit and it was too big. I need one that has the flat head so I can connect my harness wire to it. My old one only had threads and a small nut. I don't want to cut the wire and crimp on a circular terminal. I want it to look stock with the plastic end that slips over the flat head. The one I purchased was advertised on eBay as "Temperature Sender 1967 68 69 70 71 72 Chevy/GMC Truck" But when I pulled my old one out, it was much smaller. The new one required a 15/16" socket, while the old required a 3/4" socket. I pulled it from the side of the block on the driver side. The engine is a replacement 350 crate engine from a GM dealer. Help! Are there different sized temp sending units for a 350? __________________ 2018 Chevy Crew Cab 2006 Impala SS 1965 Plymouth Sport Fury 1970 Chevy Longhorn Bucket Seats Shoulder Belts Front Tow Hooks Factory Air Factory Speedwarning, Tach & Vaccum Factory Tilt CST Package AM/FM Radio Bumper Guards Richard 70 Longhorn CST Build Adding an AM/FM Decal

05-04-2009, 01:28 AM	#2
70LonghornCST Moderator Join Date: Jun 2008 Location: Modesto, CA Posts: 5,775	Re: Temperature Sending Unit ttt __________________ 2018 Chevy Crew Cab 2006 Impala SS 1965 Plymouth Sport Fury 1970 Chevy Longhorn Bucket Seats Shoulder Belts Front Tow Hooks Factory Air Factory Speedwarning, Tach & Vaccum Factory Tilt CST Package AM/FM Radio Bumper Guards Richard 70 Longhorn CST Build Adding an AM/FM Decal

05-04-2009, 01:44 AM	#3
texanidiot25 Eat My Rust Join Date: Jan 2007 Location: Cypress, Texas Posts: 3,362	Re: Temperature Sending Unit Photos of the one you have on hand, and the one you want? The one I got from Napa? was about he size of a half dollar coin, with a nail-head-like terminal. I just cut the plastic cover off the female end of regular connector and slid it over the end. Works for me, just a driver.

05-04-2009, 01:48 AM	#4
A.P. Black 72 Chevy Join Date: May 2002 Location: Los Angeles, California Posts: 662	Re: Temperature Sending Unit Scroll down to page 98 or 99. http://www.scribd.com/full/5722345?a...jcbazlklxtunnw __________________ 72 Chevy, SWB, 350engine, TH400

05-04-2009, 04:33 PM	#5
monte0185 Registered User Join Date: Oct 2008 Location: Brighton, TN Posts: 1,267	Re: Temperature Sending Unit My guess is you either have a later model set of heads that requires you to have a 3/8NPT sensor or you have an aftermarket sensor with an adaptor. The correct size is a 1/2npt thread size but if you have late model heads you will need to turn the sensor down on a lathe and rethread it or find a sensor that will work with your gauge. I have yet to find one to work with my gauge. __________________ A computer once beat me at chess, but it was no match for me at kick boxing. Duct tape is like the force. It has a light side, a dark side, and it holds the world together.

05-04-2009, 04:43 PM	#6
texanidiot25 Eat My Rust Join Date: Jan 2007 Location: Cypress, Texas Posts: 3,362	Re: Temperature Sending Unit Well what does the wrong sensor do to your gauge? With my older small block, we just ordered one that was designated for the truck. Dunno if the connector is proper, but it works.

05-04-2009, 04:49 PM	#7
monte0185 Registered User Join Date: Oct 2008 Location: Brighton, TN Posts: 1,267	Re: Temperature Sending Unit The new 3/8npt sensor will not work with the 67-72 gauge. It will read hot when its not. The ohms are different for later model gauges than ours. What are the casting #'s on your heads. I just went through all this with mine. Im running a set of 99 model vortec heads. I had to have someone turn my sensor down and rethread it. I havent had a chance to try it out yet though. __________________ A computer once beat me at chess, but it was no match for me at kick boxing. Duct tape is like the force. It has a light side, a dark side, and it holds the world together.

05-04-2009, 08:10 PM	#8
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Re: Temperature Sending Unit I had the same issue with the newer heads having smaller threads. I ended up drilling and tapping the head 1/2 NPT and using the sensor for our trucks. I had gone to NAPA and they have the ohm listing for all of the sending units but no luck on having the correct ohms in a smaller thread version of the sensors. I believe the range needed in order for the sending unit to work with the truck gauges is in the 80 to 900 ohm range, (80 ohms being hot and 900 being cold). Jim __________________ 1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC

05-05-2009, 11:14 AM	#11
sleepertruck72 Registered User Join Date: Nov 2007 Location: Turlock California 95380 Posts: 2,075	Re: Temperature Sending Unit I put my temp sending unit on my intake manifold and it works just fine. Is that an option ? My engine is a 350HO crate engine with Vortec Heads. I had to crimp on a not so stock looking terminal, but I'm sure you can find a stock looking one or somehow take the black plastic cover to the old one and get it to cover up the ugly terminal ? __________________ 72 C20 Longbed 05 1500 Z71

05-05-2009, 04:28 PM	#12
texanidiot25 Eat My Rust Join Date: Jan 2007 Location: Cypress, Texas Posts: 3,362	Re: Temperature Sending Unit The head is a more reliable point to put the sensor. Up top, given if you had a coolant leak, your sensor would no longer be reading the coolant temp, just the hot air. Which could give a false reading saying your cool, when your over heating.

05-05-2009, 08:56 PM	#13
70LonghornCST Moderator Join Date: Jun 2008 Location: Modesto, CA Posts: 5,775	Re: Temperature Sending Unit Thanks for all of the replies. I will 1st double check to see if there is a second port option for a larger sized sensor. If not, I will try some of the suggestions offered. I wonder if a different car maker has an approptiate sized sensor that will work? I know Mopar has a smaller sized sensor, but I am not sure about the OHMS. __________________ 2018 Chevy Crew Cab 2006 Impala SS 1965 Plymouth Sport Fury 1970 Chevy Longhorn Bucket Seats Shoulder Belts Front Tow Hooks Factory Air Factory Speedwarning, Tach & Vaccum Factory Tilt CST Package AM/FM Radio Bumper Guards Richard 70 Longhorn CST Build Adding an AM/FM Decal

05-05-2009, 09:23 PM	#14
powell72 Senior Member Join Date: Jan 2005 Location: Loveland Co. Posts: 3,098	Re: Temperature Sending Unit I also have the later heads and I have my sensor in the intake, works just fine. __________________ Chris 74 Custom Deluxe SWB 350/350/3.73’s 99 2wd Silverado RCSB 5.3/4L60/3.90’s http://www.classictrucks.com/feature...short_bed.html

05-05-2009, 09:24 PM	#15
highperf4x4 Account Suspended Join Date: Apr 2009 Location: Oklahoma City Posts: 4,709	Re: Temperature Sending Unit I plugged my head and moved the sending unit to the intake manifold.

05-05-2009, 10:16 PM	#16
berencam Registered User Join Date: Aug 2007 Location: branson mo Posts: 933	Re: Temperature Sending Unit try a sending unit for a set of 90s era heads, mine is the small type like your talking about. i ended up using an aftermarket gauge and mounting in the original location. __________________ 69 chevy c10 350 3 speed manual wood bed build thread here r.i.p. 70 c10 auto 350 build here

05-06-2009, 01:44 AM	#17
70LonghornCST Moderator Join Date: Jun 2008 Location: Modesto, CA Posts: 5,775	Re: Temperature Sending Unit Well, I don't have a port for a 1/2 anywhere else on the block, and the stock manifold does not have a plug anywhere I can see. However, I found this adaptor on ebay (220388003191). What do you think? It shows as 3/8" NPT male to 1/2" female. Attached Images __________________ 2018 Chevy Crew Cab 2006 Impala SS 1965 Plymouth Sport Fury 1970 Chevy Longhorn Bucket Seats Shoulder Belts Front Tow Hooks Factory Air Factory Speedwarning, Tach & Vaccum Factory Tilt CST Package AM/FM Radio Bumper Guards Richard 70 Longhorn CST Build Adding an AM/FM Decal Last edited by 70LonghornCST; 05-06-2009 at 01:44 AM.



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05-06-2009, 02:25 AM	#18
youhaveamonkey Registered User Join Date: Mar 2009 Location: Oakland, Ca Posts: 39	Re: Temperature Sending Unit I have a 350 and mine is tapped for 1/2 NPT. I would be VERY careful with an adapter like that. A brass adapter can act as a heat sink and shift the position of the sensor. The sensor was engineered to be in a specific place and it needs to be there otherwise it will give you inaccurate readings. Not that it is a a bad idea. Mechanically you could find a brass bushing that would locate the sensor in approximately the correct place.This would be all threads on the outside and inside. Should be able to get one at any plumbing supply house. But make sure it is a bushing NOT an adaptor. then you have the other problem. the output of the sensor. Don't know what to tell you about that. Best of luck. Just my .02. arrrgh, I just re-read your post. I am sorry. Never mind what I just said about the bushing. Just be careful with the adapter. Last edited by youhaveamonkey; 05-06-2009 at 02:27 AM.

05-06-2009, 09:26 AM	#19
brian mac Registered User Join Date: Dec 2008 Location: eufaula,alabama Posts: 198	Re: Temperature Sending Unit I can machine the stock style sending unit to fit head holes that are 3/8 pipe. Price is 25.00 shipped. This includes a new sending unit that has been modified. I sent one to member monte0185 but he has not installed it yet. PM me if you are interested or have questions.

08-04-2014, 12:35 AM	#23
Lead Sleader Registered User Join Date: Jul 2014 Location: Wichita Posts: 1	Re: Temperature Sending Unit Brian Mac posted that he could turn down and rethread a dual temp sender. I would like to see if he is still around and can do this for me. It is the sender for the hot and cold lights. It is in my 65 chevy impala with a 350 and late model heads and a TPI. He was the only one that had a very good idea. I am also working on a 72 Chevy pickup. Any help ....

08-04-2014, 12:16 PM	#25
74baggedbug Registered User Join Date: Oct 2011 Location: Houston tx Posts: 701	Re: Temperature Sending Unit I had mine machined down cause I'm running newer heads. That's the only way it will work so you can use the factory gauge cluster ..

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