Temperature sending unit question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

drman929 · 07-09-2007, 10:00 PM

Just got her back together and running great...

Changed over to the int reg alternator and replaced the temperature sender on the passenger side head. The temp gauge worked before pulling the motor, but now it doesn't. The sender on the passenger head broke during the engine pulling ceremony...haha

Does anyone know what needs to be grounded and where was the stock location of the ground on the temperature gauge system?

Also, the green/white wire coming off of the driver side temp sender appears to go into a flat 2 terminal black connector and ties in with a blue/white wire on one terminal . The other terminal just has one wire and I forgot its color.

Chevelle454 · 07-09-2007, 10:15 PM

Mine only has a single green wire going to the temp sender...

drman929 · 07-09-2007, 10:18 PM

Where does your wire run to after that?

pharcydekm · 07-10-2007, 12:32 AM

single green wire runs from drivers side sender to the harness on the firewall. I lose it from there but kinda hard to see after so much BEER!

drman929 · 07-24-2007, 09:57 PM

Ok, I still haven't got that sucker to work. Why does my truck have two temperature senders? As far as I can tell, this is the factory setup, but I can't remember which wire went to the one on the passenger side head. There is another green striped wire, but it doesn't work when I hook it up. Does anyone else have two temp senders that they can tell me which wires hook on to? My sender on the passenger head is a spade terminal, while the one on the drivers side head is the slip on stud type. I want my gauge to work! haha

drman929 · 07-24-2007, 10:00 PM

Also, would the wires going to the temp senders be a switched 12v source?

drman929 · 07-25-2007, 09:55 PM

I know somebody knows something about this topic!

notahybrid · 07-26-2007, 08:52 AM

Sounds like you're talking about the water temp. Not the oil temp right.... Do you have gauges on your panel or warning lights?

**john** · 07-26-2007, 01:05 PM

The sender in the pass side head was for the TCS control. That allows vacuum advance only in high gear after eng is at operating temp. The temp sender in driver side should be a dark green wire unless yours has had some rewiring.

**john** · 07-26-2007, 01:12 PM

Quote:

Originally Posted by drman929

Also, would the wires going to the temp senders be a switched 12v source?

The guages are switched 12v and the senders are the ground.

hyarbour · 07-26-2007, 02:21 PM

I thought senders with one wire were switches for warning lights, two wire senders were for gauges.

**john** · 07-26-2007, 04:08 PM

Quote:

Originally Posted by hyarbour

I thought senders with one wire were switches for warning lights, two wire senders were for gauges.

The temp ga sender is a single dark green.

kbs71 · 07-26-2007, 07:42 PM

drman929 heres some wiring diagrams to help you out. I haven't seen a green/white wire going to a blue/white wire connector before. You might want to try and putting a ground from the back of the gauge cluster (preferably one of the screws that hold the temp gauge back plate on) to a good body ground.

drman929 · 07-26-2007, 10:58 PM

Ok, thanks for the help!

About the TCS, I think I know what you all are talking about. Did they have two prongs on the back, along with 2 vacuum line connections? If so, it's not going back on. So, would I have to make a jumper wire or something to go from each terminal on the TCS connector? This is the connector that the passenger side sender leads into. I'm having trouble finding any wiring diagrams with the TCS system.

jhow66 · 07-26-2007, 11:09 PM

Quote:

Originally Posted by drman929

Ok, thanks for the help!

About the TCS, I think I know what you all are talking about. Did they have two prongs on the back, along with 2 vacuum line connections? If so, it's not going back on. So, would I have to make a jumper wire or something to go from each terminal on the TCS connector? This is the connector that the passenger side sender leads into. I'm having trouble finding any wiring diagrams with the TCS system.

Yes. No just leave it off-it controls nothing else.
Take the green wire on driver side and ground it. Now turn on switch for a second-if gauge is good the hand will go all the way right. If not then the gauge is bad or green wire is broken somewhere.

drman929 · 08-08-2007, 11:27 PM

Still haven't got this figured out. New gauge just put in, with no luck. I'm not getting 12 volts to my sending unit wire...Guess it's time to pull the harness?

Also, my dash lights aren't working. Could this be the headlight switch?

corn · 08-08-2007, 11:32 PM

All the single wire senders Ive seen were grounding senders. Sender activates the ground.

72swbcamo · 08-09-2007, 11:50 AM

If you aren't going to reconnect the TCS I could use the sending unit.
I can send you the plug that gois hack in the head if you need it. Let me know.

**VetteVet** · 08-09-2007, 02:03 PM

You need to go back and read the post replies. Especially # 10 and 13. The sending unit wires are ground wires and should not have 12 volts put to them unless you want to burn up the wires or blow fuses. When the engine coolant heats up it causes the sending unit to ground to the engine block through a built in resister. This allows a ground path to the gauge. There should be a switched 12v source to the other terminal on the gauge which will allow the gauge needle to move as the sender grounds. The check is to disconnect the sender wire and ground it to the block, with the key on it should read all the way to the left. IIRC.
There is also a resister on the back of the gauge that goes bad and will not allow current to flow through the gauge.
In post 13 KBs 71 tells you to run a ground wire to the dash to fix the dash lights and this is a common fix for that problem. The headlight switch also has a rheostat built in that dims the dash lights so it might also be the problem.
BTW it would be helpful if you would put some info in your signiture telling what year your truck is, the engine and tranny etc. It keeps the guessing game down. VV

drman929 · 08-09-2007, 10:39 PM

Hey 72swb, I got my new one at a parts store for cheap. It would probably be more efficient to buy one locally for you after shipping.

Vette, thanks for the reply. It straightened a few things out for me. I got a new headlight switch but haven't had a chance to install it, so I will try that and ground the cluster. So should three of the four terminals on the gauge be hot with the key on?

07-09-2007, 10:00 PM	#1
drman929 Registered User Join Date: Nov 2006 Location: Arkansas Posts: 232	Temperature sending unit question Just got her back together and running great... Changed over to the int reg alternator and replaced the temperature sender on the passenger side head. The temp gauge worked before pulling the motor, but now it doesn't. The sender on the passenger head broke during the engine pulling ceremony...haha Does anyone know what needs to be grounded and where was the stock location of the ground on the temperature gauge system? Also, the green/white wire coming off of the driver side temp sender appears to go into a flat 2 terminal black connector and ties in with a blue/white wire on one terminal . The other terminal just has one wire and I forgot its color.

07-09-2007, 10:15 PM	#2
Chevelle454 Registered User Join Date: Aug 2003 Location: MN Posts: 380	Re: Temperature sending unit question Mine only has a single green wire going to the temp sender... __________________ 1972 C10 1972 C20

07-09-2007, 10:18 PM	#3
drman929 Registered User Join Date: Nov 2006 Location: Arkansas Posts: 232	Re: Temperature sending unit question Where does your wire run to after that?

07-10-2007, 12:32 AM	#4
pharcydekm Registered User Join Date: May 2003 Location: Englewood, CO Posts: 146	Re: Temperature sending unit question single green wire runs from drivers side sender to the harness on the firewall. I lose it from there but kinda hard to see after so much BEER!

07-24-2007, 09:57 PM	#5
drman929 Registered User Join Date: Nov 2006 Location: Arkansas Posts: 232	Re: Temperature sending unit question Ok, I still haven't got that sucker to work. Why does my truck have two temperature senders? As far as I can tell, this is the factory setup, but I can't remember which wire went to the one on the passenger side head. There is another green striped wire, but it doesn't work when I hook it up. Does anyone else have two temp senders that they can tell me which wires hook on to? My sender on the passenger head is a spade terminal, while the one on the drivers side head is the slip on stud type. I want my gauge to work! haha

07-24-2007, 10:00 PM	#6
drman929 Registered User Join Date: Nov 2006 Location: Arkansas Posts: 232	Re: Temperature sending unit question Also, would the wires going to the temp senders be a switched 12v source?

07-25-2007, 09:55 PM	#7
drman929 Registered User Join Date: Nov 2006 Location: Arkansas Posts: 232	Re: Temperature sending unit question I know somebody knows something about this topic!

07-26-2007, 08:52 AM	#8
notahybrid Registered User Join Date: Mar 2007 Location: Chesapeake, Virginia Posts: 39	Re: Temperature sending unit question Sounds like you're talking about the water temp. Not the oil temp right.... Do you have gauges on your panel or warning lights?

07-26-2007, 01:05 PM	#9
john member #16 Join Date: Dec 1999 Location: Yuba City Ca. Posts: 3,618	Re: Temperature sending unit question The sender in the pass side head was for the TCS control. That allows vacuum advance only in high gear after eng is at operating temp. The temp sender in driver side should be a dark green wire unless yours has had some rewiring. __________________ john http://67-72chevytrucks.com/vboard/showgroups.php board vendors http://www.flickr.com/photos/1745471...7602865984234/

07-26-2007, 02:21 PM	#11
hyarbour Registered User Join Date: Jan 2007 Location: Fairview, ks Posts: 203	Re: Temperature sending unit question I thought senders with one wire were switches for warning lights, two wire senders were for gauges.

07-26-2007, 07:42 PM	#13
kbs71 71 rustless in texas Join Date: Aug 2004 Location: Houston, TX Posts: 257	Re: Temperature sending unit question drman929 heres some wiring diagrams to help you out. I haven't seen a green/white wire going to a blue/white wire connector before. You might want to try and putting a ground from the back of the gauge cluster (preferably one of the screws that hold the temp gauge back plate on) to a good body ground. Attached Images __________________ "The secret to creativity is knowing how to hide your sources." "No one really listens to anyone else, and if you try it for a while you'll see why" 71 C-10 LWB presently in a perpetual state of disassembly '96 Toyota (my work car) '04 Mustang Convertable (wife's car & other money pit) Latest aquesition and why my trucks still in the garage covered with junk.. 2010 Aqua Blue metallic 6 speed Manual LS3 2SS/RS Camaro (I want one of these in my truck FAQ here VENDORS here SUPPORT THE BOARD here My second favorite SITE Last edited by kbs71; 07-26-2007 at 07:42 PM.

07-26-2007, 10:58 PM	#14
drman929 Registered User Join Date: Nov 2006 Location: Arkansas Posts: 232	Re: Temperature sending unit question Ok, thanks for the help! About the TCS, I think I know what you all are talking about. Did they have two prongs on the back, along with 2 vacuum line connections? If so, it's not going back on. So, would I have to make a jumper wire or something to go from each terminal on the TCS connector? This is the connector that the passenger side sender leads into. I'm having trouble finding any wiring diagrams with the TCS system.

08-08-2007, 11:27 PM	#16
drman929 Registered User Join Date: Nov 2006 Location: Arkansas Posts: 232	Re: Temperature sending unit question Still haven't got this figured out. New gauge just put in, with no luck. I'm not getting 12 volts to my sending unit wire...Guess it's time to pull the harness? Also, my dash lights aren't working. Could this be the headlight switch?

08-08-2007, 11:32 PM	#17
corn Registered User Join Date: Dec 2003 Location: here Posts: 5,789	Re: Temperature sending unit question All the single wire senders Ive seen were grounding senders. Sender activates the ground.

08-09-2007, 11:50 AM	#18
72swbcamo Active Member Join Date: Dec 2003 Location: Waterbury, CT Posts: 591	Re: Temperature sending unit question If you aren't going to reconnect the TCS I could use the sending unit. I can send you the plug that gois hack in the head if you need it. Let me know.



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08-09-2007, 02:03 PM	#19
VetteVet Msgt USAF Ret Join Date: Jan 2005 Location: Kalamazoo, Michigan Posts: 8,709	Re: Temperature sending unit question You need to go back and read the post replies. Especially # 10 and 13. The sending unit wires are ground wires and should not have 12 volts put to them unless you want to burn up the wires or blow fuses. When the engine coolant heats up it causes the sending unit to ground to the engine block through a built in resister. This allows a ground path to the gauge. There should be a switched 12v source to the other terminal on the gauge which will allow the gauge needle to move as the sender grounds. The check is to disconnect the sender wire and ground it to the block, with the key on it should read all the way to the left. IIRC. There is also a resister on the back of the gauge that goes bad and will not allow current to flow through the gauge. In post 13 KBs 71 tells you to run a ground wire to the dash to fix the dash lights and this is a common fix for that problem. The headlight switch also has a rheostat built in that dims the dash lights so it might also be the problem. BTW it would be helpful if you would put some info in your signiture telling what year your truck is, the engine and tranny etc. It keeps the guessing game down. VV __________________ VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative.

08-09-2007, 10:39 PM	#20
drman929 Registered User Join Date: Nov 2006 Location: Arkansas Posts: 232	Re: Temperature sending unit question Hey 72swb, I got my new one at a parts store for cheap. It would probably be more efficient to buy one locally for you after shipping. Vette, thanks for the reply. It straightened a few things out for me. I got a new headlight switch but haven't had a chance to install it, so I will try that and ground the cluster. So should three of the four terminals on the gauge be hot with the key on?

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