I have no indication on my coolant gage. It stays below the C. I have changed the temp sender (two wire sensor at back of engine) and it still doesn't work. I ground the red/white wire that connects to the sensor and the gage in the trucks pegs above high so I'm thinking the wires and gage are good. Now I'm getting a check engine light. I read it and it's a P0125 Closed Loop Fuel Control Insufficient Coolant temp. Does anyone have any solutions for me? Thanks in advance.
When you replaced the sending unit, did you use a tape type ribbon dope on the sending units pipe threads, to seal them????
If so & you used too much, it may have insulated the sending units threads, by preventing them from making physical contact with the engine block, thus giving you an open ground connection.
So, check the sending units cold temp electrical resistance to ground.
If it appears to be very high or infinate resistance, suspect thats the problem.
You can check this out, by applying a good connection, chassis to sending unit case, jumper wire & re-checking the sending units resistance.
If you don't have an ohm meter, just apply the jumper, warm the engine & see if the gauge works. If so, you'll know too much pipe thread ribbon dope was likely used.
So, remove the sending unit & ribbon dope, apply some LIQUID thread sealant, like Loctite PST-565.
It'll squeeze out between the threads, allowing good physical & electrical contact with the block threads.
If your in a hurry to drive the vehicle after the repair, you can use Locquic accelerator "N" to speed things up.
You can get the PST-565 in a small .2 oz tube P/N 56507. Most autopars stores carry this type thread sealant.
Use this type sealant ONLY on metal pipe threads, DON'T use it on non metal plastic, or composit material threads, as it can cause some of them to stress crack, when you snug them up.
Thanks for the idea. I had already checked that and verified resistance between block and sensor. I am completely stumped with this problem. I have electrical schematics of the gage, coolant sensor, PCM, and all wires and have checked all of them. All are good. My truck seems to heat up fine so I don't think it's an open stat. I think I'm going to drain the antifreeze and change the stat. Any other suggestions as to something I am missing would be appreciated. Thanks.
Well right now only two other things come to mind, maybe you were given the wrong value sending unit!!!!
Could be the wrong part, or maybe the factory put the right P/N on the wrong part!!!!
SO, warm the engine & check the sending units electrical resistance, do this both warm & cold, to make sure it's within the sending units specification.
I know you said the temp gauge would peg if you grounded it, but another thing you could do to double check the gauge, is to simulate the sending units resistance with separate resistors, of say 1/4 watt size.
Remove the electrical connector from the sending unit.
Connect one end of a resistor to the wiring harness contact, the other to ground, switch the ignition to run & check the gauge. If you've chosen the correct resistance values, you should be able to cause the gauge to read, hot/normal/cold & verify it'll carry the current & read as it should.
You could come by the resistors at RadioShack or the like, if you don't have any laying around.
Once you confirm the gauge will respond & read properly with a known resistance, then you can concentrate on the sending unit.
It's really a very simple circuit, just a current source(the battery), a milliamp meter(the temp gauge), connected to ground through a thermistor(the sending unit), who's resistance value changes at a known rate, with temperature.
So, seems to me, if the gauge doesn't read anything, you have an open circuit, or the wrong value resistance in the sender, or a bad ground.
This forum is owned and operated by Internet Brands, Inc., a Delaware corporation. It is not authorized or endorsed by the Ford Motor Company and is not affiliated with the Ford Motor Company or its related companies in any way. FordŽ is a registered trademark of the Ford Motor Company.