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help with temp sending unit
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dmac0923
Enthusiast
Jul 15, 2012, 5:40 PM
Post #1 of 10
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help with temp sending unit
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i have a 1969 mustang with a 1970 mustang 351 cleveland motor. The temp gauge is not giving me a reading. I did some research online and found that if I take the wire connector off of the sending unit and touch it to a good ground the temp gauge should peg at the Hot mark. (which it does so i know the gauge is working)
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2015 Jeep Grand Cherokee
2002 Ford Ranger
2004 Toyota Corolla
1969 Ford Mustang Mach 1
(This post was edited by dmac0923 on Jul 16, 2012, 6:54 PM)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 15, 2012, 6:02 PM
Post #2 of 10
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Re: which temp sending unit
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Either readily available with a quick check. One for just plain "idiot" light and one for gauge and plain can't recall if all '69 'Stangs were the same dash or not?
They did put the 351C (nuke power!) in "sleeper cars" I called them which were just plain Jane's but road burners,
T
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dmac0923
Enthusiast
Jul 16, 2012, 6:55 PM
Post #3 of 10
(6409 views)
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temp sending unit
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So i went to carquest and picked up a new sending unit and double checked it was a unit for a gauge car not an idiot light and installed it......still nothing on the gauge....
am i missing something here guys?
__________________________________________________
2015 Jeep Grand Cherokee
2002 Ford Ranger
2004 Toyota Corolla
1969 Ford Mustang Mach 1
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 16, 2012, 11:09 PM
Post #4 of 10
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Re: temp sending unit
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Memory shot - what's new? OK - I think Ford made some changes between MY 1969 and 1970 with things like that. Either way if gauge is just sitting on the lowest area of dash gauge something is messed up. No quotes on this but a single wire gauge sender is just changing ohms thru it to ground based on temp such that unplugged or wiring open somewhere would read lowest on dash and grounded would read highest if grounded. I think that's ruled out at the sensor which can be checked if just for changing ohms.
1960's Ford did pull a trick of lowering voltage used for some TMK such that the dash unit was based on 6 volt system and could read incorrectly but still change.
Need to know that the gauge can move at all. Now an antique car and open to lots of things.
With engine change did anything get physically bumped or damaged that could mess up some wiring?
T
(edited out a typo)
(This post was edited by Tom Greenleaf on Jul 17, 2012, 7:28 AM)
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dmac0923
Enthusiast
Jul 17, 2012, 7:08 AM
Post #5 of 10
(6354 views)
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Re: temp sending unit
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If I take the wiring harness off of the sending unit and ground it on the engine block the temp gauge needle swings fully to the Hot mark
__________________________________________________
2015 Jeep Grand Cherokee
2002 Ford Ranger
2004 Toyota Corolla
1969 Ford Mustang Mach 1
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 17, 2012, 7:22 AM
Post #6 of 10
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Re: temp sending unit
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OK - That suggests no problem with the needle gauge itself. Forget exact year right now but think it was a '69 Mustang just 10 miles from me and owner found me at this site for some hands on checking things and HE knew of this 6V/12V thing and I didn't! His temp gauge would start off cold was cold but go up to near max when normally warmed up and wasn't overheating. Wasn't the reason I went over there as he just needed some carb adjustments but noticed the dang gauge like that and checked actual temps as I had stuff with me.
What is the new sender doing or nothing at all? Would be hard to believe the old one and a new one both were totally defective to do anything??
T
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dmac0923
Enthusiast
Jul 17, 2012, 9:57 AM
Post #7 of 10
(6332 views)
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Re: temp sending unit
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Yea when i connect the wiring harness to the sender i get no response in the gauge at all
__________________________________________________
2015 Jeep Grand Cherokee
2002 Ford Ranger
2004 Toyota Corolla
1969 Ford Mustang Mach 1
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 17, 2012, 10:25 AM
Post #8 of 10
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Re: temp sending unit
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Getting there. I take this that the same plug when grounded does get a response? If so make sure connection is right and tight then plain OHM test the sender(s) new and old or perhaps try an incandescent test light between plug wire and sender and again at ground for a response. Try an LED one first but may not draw enough for squat for this.
Smile - if this were tons newer I wouldn't be suggesting that but is a cheap easy test and I know this is going to lead to me digging out what OHMs at what temperature should read but apparently since no reaction at gauge itself not doing much at all now,
T
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dmac0923
Enthusiast
Jul 17, 2012, 4:29 PM
Post #9 of 10
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Re: temp sending unit
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yea its the same connection from the sending unit that i was grounding out.
i did some research about the 6v reduction, and on the back of the instrument cluster is a voltage regulator that drops it down to 6V. but apparently if that is bad all of the gauges would be affected not just the one.
__________________________________________________
2015 Jeep Grand Cherokee
2002 Ford Ranger
2004 Toyota Corolla
1969 Ford Mustang Mach 1
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jul 18, 2012, 1:19 AM
Post #10 of 10
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Re: temp sending unit
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It should do something at assorted engine temps even if wrong.
Is engine to body well grounded AND body to dash well grounded?
I think I'd be checking the sender in a pan of water on stove about now to see it change or not.
Other test could be does a test light, light on what should be grounded to engine part of the sender itself or is it possibly so insulated by perhaps Teflon tape if used or something that isolates it?
Tom
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