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Author
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Topic: Temperature guage problem 1970 Fastback 351C 2V
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RobertsMustang
Journeyman Posts: 2
From: Victoria, Australia
Registered: Dec 2003
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posted 12-18-2003 06:54 PM
  
I recently bought a 1970 Mustang Fastback - 351 Cleveland 2V - temp guage wasn't working - replaced sender unit - it worked but temp reading appeared too high - 3/4 up the guage at operating temp. Had radiator & engine flushed - very little dirt etc, couple of small leaks fixed, new 180 degree thermostat (suited to Clevelands) installed, new coolant. Guage still read the same. Replaced sender unit again with one suited to Mustang guage - guage now reads past H after travelling only a short distance. At operating temp coolant is 182 degrees, coolant doesn't flow out radiator when cap is off, doesn't bubble at fast idle, combustion test okay, can put hand around top hose, water pump OK, no oil in radiator, no water in oil,no significant loss of coolant, belt tension ok, engine runs smoothly. Can only assume a guage problem. Spoke to auto electrician who said he needs to know ohms resistance readings for guage. For sender unit it is 220 degrees 18.49 to 15.75 ohm, 100 = 150 to 100 ohms.
PS - Could it be the constant voltage regulator to the instrument panel
Have a great Xmas ------------------
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RonnieT
Gearhead Posts: 727
From: Port Allen, La. 70767
Registered: Jun 99
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posted 12-18-2003 08:47 PM
When the instrument panel voltage regulator starts acting up it will affect all the gauges, so your oil pressure and fuel gauge would also read high if that is the problem. Where is the gauge reading when the coolant temp is 182? I am not sure what the ohm readings are supposed to be for the gauge, maybe someone else will know. ------------------
Ronnie
69 mach1 351W-4V engineless at the time!
70 Torino GT 351C-4v with a "shaker"
Mustangs and More Member #23
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johnmustang
Gearhead Posts: 4933
From: British Columbia , Canada
Registered: Nov 2001
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posted 12-18-2003 09:07 PM
Hook up an external guage first and test it that way, then proceed from there. Just sounds like the Gage is pooched.------------------
JOHN
65 FASTBACK 2+2.....14.44 @ 107mph 1/4
87 TAURUS WAGON
03 F150 XLT SUPER CREW 4X4 SHORT BOX
Member:Vancouver Island Mustang Association
M&M #1710
65 FASTBACK
2003 F150 XLT SUPER CREW 4X4
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wvcat
Gearhead Posts: 231
From: New Cumberland,WV
Registered: May 2001
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posted 12-18-2003 10:46 PM
I was having a similar problem with my 70 cougar. Chased the problem all summer. Checked my engine with a infared thermometer and it was normal. Traced the problem to the ground wire. On a 69 there is a strap from the firewall to the back of the head and on a 70 there is a clamp made in the middle of the battery ground wire that grounds the body. Mine didn't have either. I just installed a firewall strap and all is well.
John
wvcat------------------
Thanks
John
(wvcat)
http://www.geocities.com/wvxr7cougar/wvcat_01.html?989286238390
70 XR7 Restomod...wvcat
66 coupe project...she needs a name!!!
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V8 Thumper
Gearhead Posts: 3936
From: Orange, Ca. United States of America
Registered: Dec 2001
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posted 12-19-2003 08:56 AM
Welcome to M&M Robert!  ------------------
1965 GT coupe, 333ci aluminum headed/solid cammed stroker, four speed, 3.70:1 9" All Blue Oval, no blue bottle
http://mustangsandmore.50megs.com/V8Thumper.html
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kid vishus
Gearhead Posts: 5105
From: middle of NC
Registered: Oct 2000
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posted 12-19-2003 07:11 PM
Welcome to M&M.Personally, I don't trust factory guages. I want actual readings, not guess-timations. Till you get an accurate guage, you will never know the actuall temp of the motor. Same goes for oil pressure. ------------------
Rob Hetzler
member #773
'69 mustang, 351C, best 9.97 @ 133 mph 1/4, 6.18 @ 110.4 1/8
'70 mustang,351W powered (KK's racecar)
'93 F150 Lightning 15.33 @ 87 mph, completely stock with 184k miles
'60 Falcon wagon project car
'99 Pro Et track champion
'00 Mod ET R-up (with new car) My Photo Page
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V8 Thumper
Gearhead Posts: 3936
From: Orange, Ca. United States of America
Registered: Dec 2001
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posted 12-19-2003 07:18 PM
Agreed. The very reason I have mechanical gauges for water temp and oil pressure  ------------------
1965 GT coupe, 333ci aluminum headed/solid cammed stroker, four speed, 3.70:1 9" All Blue Oval, no blue bottle
http://mustangsandmore.50megs.com/V8Thumper.html
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RobertsMustang
Journeyman Posts: 2
From: Victoria, Australia
Registered: Dec 2003
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posted 12-21-2003 07:31 AM
Thanks everyone. And thanks for the welcomes. Happy New Year, Merry XmasRonnie T - at 182 degrees the guage reads almost to H, oil pressure guage reads at H from ignition point, I have suspected fuel guage doesn't read correctly - but showing less fuel than there actually is. WVCAT - my brother actually suggested a possible earth problem which I will check out in the morning. Agree about the guages
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RonnieT
Gearhead Posts: 727
From: Port Allen, La. 70767
Registered: Jun 99
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posted 12-21-2003 11:30 PM
Since all the gauges are reading incorrectly it could be the instrument cluster voltage regulator. A bad ground will typically make the gauges read low, not high. If the regulator is allowing too high a voltage it will cause all the gauges to read high. Since the oil pressure is reading high as soon as the key is turned on it sounds like you may have wiring problem. The printed circut boards are known to cause problems and I think are now available as a reproduction to get things working back like they should.------------------
Ronnie
69 mach1 351W-4V engineless at the time!
70 Torino GT 351C-4v with a "shaker"
Mustangs and More Member #23
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