1968FormulaS340
Well-Known Member
Mine is not working. Have tried 3 sending units and no luck. It just sits on zero. When I ground the sending unit wire the gauge moves to the full hot side. Anyone have an idea?
68 Barracuda Formula S 340 temp gauge question.
- Thread starter 1968FormulaS340
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1968FormulaS340 said:
Huh? If you ground the sending unit wire and the gauge moves, that pretty much rules out the circut. Are you using a thread sealant on the sending unit threads? Teflon tape maybe? You might be insulating the grounding of the sending unit. Try cleaning the treads in the intake manifold. Also make sure you have no air pockets in the cooling system. Jack up the nose of the car and let it idle with the radiator cap off. Watch for the coolant to circulate.
Let us know how you make out.....:-s
dgc333
Well-Known Member
Are you sure you have a sending unit for a guage and not one for an idiot light? The idiot type have a bi-metallic strip inside and it will not move over to ground the light until the temp reaches 230or so.
The easiest way to visually tell is the guage sender will have a cylindirical end that goes into the coolant passage. The idiot light type will have a pinched end.
If you have a multimeter you can test them to and this would be the best way. Connect one lead to the terminal and the other to the body of the sensor and set the multimeter to the resistance scale. Drop the sensor with the leads attached into a pot of boiling water. The resistance should move towards zero
The easiest way to visually tell is the guage sender will have a cylindirical end that goes into the coolant passage. The idiot light type will have a pinched end.
If you have a multimeter you can test them to and this would be the best way. Connect one lead to the terminal and the other to the body of the sensor and set the multimeter to the resistance scale. Drop the sensor with the leads attached into a pot of boiling water. The resistance should move towards zero
1968FormulaS340
Well-Known Member
Yes this is a head scratcher. I was thinking the sealant was not letting it ground so I cleaned all the threads. It is the correct sending unit. What I am thinking now is..... I have an after market intake and use an adapter to mount the unit. (Hole in the intake water passage is to large to mount the sender directly.) The sending unit is flush with the end of this adapter...
So none of the sending unit extends directly into the coolant path only the surface area on the flat end is directly exposed.
Sound like this could be it?
So none of the sending unit extends directly into the coolant path only the surface area on the flat end is directly exposed.
Sound like this could be it?
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1968FormulaS340 said:
Hmmm.... maybe. A small air pocket could cause this. Let us know....:?
1968FormulaS340
Well-Known Member
Ok. I worked on the temp gauge issue all day today. I removed the cluster, cleaned the terminals. Hogged out the fitting the sending unit fits in to allow more coolant to come in contact with the sender. Removed all sealant on threads. Filled the hole the sender goes into with water and inserted sender to ensure no air pocket. Ran a wire from the sender terminal to the sender to make sure the harness wire was not the problem. No luck it still will only move if I ground the sender wire (or the new direct sender wire).
Other things.....
My gas gauge has a more accurate and free movement after cleaning.
My oil pressure gauge moves slow now and does not move sa far as it once did. (new problem)
I put a tester (one of the things with a ground wire and a metal probe with a light in the handle) on the temp sender wire. the light in the handle flickers on and off but does not stay on.
A note on my charging system...
My car looks stock but the original 340 is extremely built. polished rods, 11.5 compression, crower street solid roller cam (290dur. .550lift), pro ported heads. Basically with slicks and at the track I hold the rpm at 8000 with the line lock on dump the clutch and run an 11.8 @ 118 in the 1/4. With the extreme RPM I have a larger pulley on the alternator to prevent it from turning to fast and ripping its guts out.
The car does not charge at an Idle don't think this would have anything to do with the gauge at cruise. Also my dash and head lights flicker as I drive down the road.
Just wanted to get all that out if it may be related.
FYI an 8 3/4 will not take an 8000 rpm clutch dump for long so I run a dana 60.
http://www.s14.net/photopost/showphoto.php?photo=4400
Other things.....
My gas gauge has a more accurate and free movement after cleaning.
My oil pressure gauge moves slow now and does not move sa far as it once did. (new problem)
I put a tester (one of the things with a ground wire and a metal probe with a light in the handle) on the temp sender wire. the light in the handle flickers on and off but does not stay on.
A note on my charging system...
My car looks stock but the original 340 is extremely built. polished rods, 11.5 compression, crower street solid roller cam (290dur. .550lift), pro ported heads. Basically with slicks and at the track I hold the rpm at 8000 with the line lock on dump the clutch and run an 11.8 @ 118 in the 1/4. With the extreme RPM I have a larger pulley on the alternator to prevent it from turning to fast and ripping its guts out.
The car does not charge at an Idle don't think this would have anything to do with the gauge at cruise. Also my dash and head lights flicker as I drive down the road.
Just wanted to get all that out if it may be related.
FYI an 8 3/4 will not take an 8000 rpm clutch dump for long so I run a dana 60.
http://www.s14.net/photopost/showphoto.php?photo=4400
Longgone
John/68 Barracuda & Dart
Hey 68 ,did you ever find out what was causing your test light to flicker on and off here? I`ve got the same scenario ,posted a forum ,but no one wants to take a stab at it.Any help?
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