Temp Gauge - 351M -
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Freshman User
Joined: Jan 2006
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From: DFW, Texas
Temp Gauge - 351M -
I'm looking to find a stock or similiar temp gauge for my 77 351M. The gauge recently went dead and was the orig. equipment.
I replaced the sending unit, thermostat & have put in a new radiator as the truck was starting to run hot from the orig. radiator before the gauge failed.
The guage is deader than a doornail, so I checked the junk-yards and found two gauges from a 78 Bronco & a 77 f150. I tried both in the truck, & both gauges spike the temp reading to the max !!! I had a mechanic do an infrared reading on the temp of the engine, and all was normal on two readings at varying lengths of engine run time/speeds. I assume these two gauges are faulty as well. The posts were not in the best of shape.
Anywhere I can buy a new 1977 style temp gauge??? I can't find any in the catalogs. I'd rather not put in an aftermarket as I want to keep the stock look.
Thanks again folks...
I replaced the sending unit, thermostat & have put in a new radiator as the truck was starting to run hot from the orig. radiator before the gauge failed.
The guage is deader than a doornail, so I checked the junk-yards and found two gauges from a 78 Bronco & a 77 f150. I tried both in the truck, & both gauges spike the temp reading to the max !!! I had a mechanic do an infrared reading on the temp of the engine, and all was normal on two readings at varying lengths of engine run time/speeds. I assume these two gauges are faulty as well. The posts were not in the best of shape.
Anywhere I can buy a new 1977 style temp gauge??? I can't find any in the catalogs. I'd rather not put in an aftermarket as I want to keep the stock look.
Thanks again folks...
Cargo Master
Joined: Apr 2001
Posts: 2,364
Likes: 3
From: Eustis FL
Someone may have sold you the wrong sending unit. The units made for a dummy light will not work right on an analog gauge.
It has happened to me once... I don't know of any vehicle that has a dummy light for temp, but they sold me one!
Mark
It has happened to me once... I don't know of any vehicle that has a dummy light for temp, but they sold me one!
Mark
Posting Legend
Joined: Sep 2001
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Not only will the wrong sender spike the gage (only when the engine overheats) but an inoperative instrument panel voltage regulator can do the same thing or a short in the wiring. When the IPVR does not work properly all the gages read high. Usually to fix the IPVR problem a good cleaning of the flex circuit and coating all if the connections with silicone dielectric grease works. A temp gage does not have to come from a truck. Vans thru about 88 also had the same gage cluster. Check the FAQ at the top of the forum for more info.
Shotgunning parts is expensive. It is much better to spend the bucks on a good service manual and run tests before replacing parts.
Shotgunning parts is expensive. It is much better to spend the bucks on a good service manual and run tests before replacing parts.
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Freshman User
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From: DFW, Texas
I could be clueless here, but by dummy light, you mean the modern day "F. Me" lights ?? Are the sending units for the newer model fords the same size as a '77 351M?? The guage was dead off of the old sending unit, and was dead with the new sending unit, leading me to replace the guage. I put in a new sending unit to kill two birds with one stone while I was playing mechanic on the gauge!!
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Did you touch the wire to the sending unit to ground.... with the key on..... and see if the gauge pegged ?
There were 2 SU's available.
One for Idiot lights & One for Gauges.
There were 2 SU's available.
One for Idiot lights & One for Gauges.
Last edited by Torque1st; Apr 12, 2006 at 11:08 PM.
Posting Legend
Joined: Sep 2001
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dummy light == idiot lights == signal lights. The newer vehicles use a dummy gage that hooks to a idiot light switch sender. The gauge reads midway until the sender switch is operated sending the needle high. The dummy gages are far worse than ANY idiot light or gage. The sender must be the right one for the application.
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Freshman User
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From: DFW, Texas
Ok.... I may have the wrong unit. Here's some background. The old gauge read mid-way at idle and 60% at highway speeds..for as long as I can remember. The gauge went dead & with the orig. radiator, I thought it was time to replace the Rad, SU, thermostat & gauge to start on an even keel after 25 + years of orig. equip.
1) get SU... put in... gauge still does not work. Take the gauge out, and the internal wires are seperated from the posts. Bad Gauge.
2) get gauges from yard...temp goes straight to 75%... and max at highway....thought is rad. is about on last leg.
3) get new rad & thermostat.... temp goes straight to 50% at idle ( 1 min)..75% at slow speeds & max at highway....infrared test show engine at normal temps.
My thought is the gauges are worn & I may have bought the wrong SU. It was cheap, so I guess I'll look into a new SU and use some more conversation with the parts person.
I still want a new gauge for peice of mind...I don't trust how old/bad these gauges are from the junkyard.
1) get SU... put in... gauge still does not work. Take the gauge out, and the internal wires are seperated from the posts. Bad Gauge.
2) get gauges from yard...temp goes straight to 75%... and max at highway....thought is rad. is about on last leg.
3) get new rad & thermostat.... temp goes straight to 50% at idle ( 1 min)..75% at slow speeds & max at highway....infrared test show engine at normal temps.
My thought is the gauges are worn & I may have bought the wrong SU. It was cheap, so I guess I'll look into a new SU and use some more conversation with the parts person.
I still want a new gauge for peice of mind...I don't trust how old/bad these gauges are from the junkyard.
Cargo Master
Joined: Apr 2001
Posts: 2,364
Likes: 3
From: Eustis FL
I don't trust the gauge on my '76. My '78 was great, however.
I will plumb in a new aftermarket gauge for peace of mind.
I suggest the same for you; Keeping the stock one in place just so everything from factory still finctions, even 'somewhat'.
Mark
I will plumb in a new aftermarket gauge for peace of mind.
I suggest the same for you; Keeping the stock one in place just so everything from factory still finctions, even 'somewhat'.
Mark
Posting Legend
Joined: Sep 2001
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The infrared thermometers are not very accurate unless the emissivity of the object is known. A better method is using a thermometer or probe in the top of the radiator and figure it is 5-10° less than the outlet temperature. With this you can get an idea of the calibration of the gage and sender so you know when hot is hot and save the time and $$ spent on installing an aftermarket unit. Instead wire up a conventional idiot light for your oil pressure and water temp to serve as a failure indicator. On some trucks there are unnecessary signal bulbs in the gage cluster that can be utilized.
Figure out what took the original gage out. Sounds like a short to ground which will burn out the gage fairly rapidly. Examine all the wire since it could happen again. The wrong sender can also short out or ground the wire and destroy a gage. A bad engine or body ground can also take out a gage.
Figure out what took the original gage out. Sounds like a short to ground which will burn out the gage fairly rapidly. Examine all the wire since it could happen again. The wrong sender can also short out or ground the wire and destroy a gage. A bad engine or body ground can also take out a gage.
Last edited by Torque1st; Apr 13, 2006 at 02:14 AM.
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Freshman User
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From: DFW, Texas
I'll get in there this week-end. I'll run a test on the gauge, SU & check the wires, plus do some more thorough checks. My first instinct of this being a minor gauge probelm may or may not be right.
I'll spend the $$$ on getting the proper wiring, SU and stock gauge or getting it fixed properlyif I have to. I have absolutely no desire to have an aftermarket gauge installed anywhere. I personally don't like the look of gauges hanging off somewhere, even hidden. Just my crazy ways.
I'll spend the $$$ on getting the proper wiring, SU and stock gauge or getting it fixed properlyif I have to. I have absolutely no desire to have an aftermarket gauge installed anywhere. I personally don't like the look of gauges hanging off somewhere, even hidden. Just my crazy ways.
Cargo Master
Joined: Apr 2001
Posts: 2,364
Likes: 3
From: Eustis FL
I don't like gauges hanging off somewhere either, unless it's a tach.
I have a dead 2" tach mounted above the headlight switch that looks factory. That is where I will put my temp gauge.
I wouldn't mess with the thermometer when there are easy ways to install a good gauge, and they aren't expensive in the first place... Besides, how can you put a price on such an important engine monitoring device?
Mark
I have a dead 2" tach mounted above the headlight switch that looks factory. That is where I will put my temp gauge.
I wouldn't mess with the thermometer when there are easy ways to install a good gauge, and they aren't expensive in the first place... Besides, how can you put a price on such an important engine monitoring device?
Mark
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