[lmfelts]

I seem to be having some difficulty in locating the CORRECT water temp sending unit for my 1993 Mustang LX 5.0. I have purchased several, Standard products, Autolite, and Motorcraft, with the same results of temp indicating too low on the instrument cluster gauge. All other gauges are performing correctly. I have checked the gauge according to my Ford shop manual using a variable resistor, 74 ohms for cold and 10 ohms for hot. The gauge seems to respond well or at least within some small degree of error. Grounding the sender wire results in the gauge going to full scale. Checking the resistance value on the senders I've purchased display anywhere between 258 to 350 ohms at ambient temp, ~70 F which appears to be too much resistance. So far, my gauge has only reflected a low temp after the car has been driven or, at least, allowed to warm up to operating temp with 180 deg thermostat. Has anyone else experienced this issue? I'm at a loss in trying to find a sender to make my gauge indicate correctly. Thanks in advance.

 

[Cobrajet67]

I seem to be having some difficulty in locating the CORRECT water temp sending unit for my 1993 Mustang LX 5.0. I have purchased several, Standard products, Autolite, and Motorcraft, with the same results of temp indicating too low on the instrument cluster gauge. All other gauges are performing correctly. I have checked the gauge according to my Ford shop manual using a variable resistor, 74 ohms for cold and 10 ohms for hot. The gauge seems to respond well or at least within some small degree of error. Grounding the sender wire results in the gauge going to full scale. Checking the resistance value on the senders I've purchased display anywhere between 258 to 350 ohms at ambient temp, ~70 F which appears to be too much resistance. So far, my gauge has only reflected a low temp after the car has been driven or, at least, allowed to warm up to operating temp with 180 deg thermostat. Has anyone else experienced this issue? I'm at a loss in trying to find a sender to make my gauge indicate correctly. Thanks in advance.

If you bought the same type of senders of various brands as what you removed then it seems that it's not the sending units that are the problem. A Motorcraft will be the best that you can buy.
How do you know that the temp is actually reading too low compared to the specific coolant temp? You should measure the actual temp where the sensor is located with a heat gun.
Perhaps your thermostat is stuck open. If so, then you would never get up to proper operating temperature. If you're currently using a 180° thermostat especially in winter then it's likely too low. You're supposed to have a 192° thermostat.
The only other possibility is a bad connection somewhere between the sender connector and the gauge in the cluster or a bad gauge.

 

[Roachwe]

Could be as simple to as the thermostat is hung open?

 

[Cobrajet67]

Perhaps your thermostat is stuck open.