When I bought my 01 Ranger a little over a month ago I noticed the coolant temp gauge wasn't working. Being a previous Ranger owner I knew the sensors are known for going out. Get one for the local parts store and of course it's the wrong one. Get one from my buddy at Ford and it works/ed great. Today when towing a trailer for the first time while cruising in the interstate I noticed the gauge was really C. After getting to where I was going and let it idle it came back up to normal. Any idea?

Wayne

 

Just so we are on the same page, your 2001 has the 2.5L SOHC Lima 4cyl engine.

In mid-2001 Ford switched Rangers over to the 2.3l DOHC Mazda L engine, Ford called it a Duratec engine, but Ford called quite a few engines Duratec, lol, I guess they liked that name.

So that can be confusing for 2001 model year
All 2000 Rangers would have the 2.5l SOHC Lima
All 2002 Rangers would have the 2.3l DOHC Duratec

All fuel injected engines had 2 coolant temp reading devices, until mid 2000's.
ECT(engine coolant temp) sensor, 2 wires, only used by the computer
ECT(engine coolant temp) sender, 1 wire, only used by dash board gauge

On the 2.5l the sender is on drivers side toward the back of the engine, near oil pressure sender.

Drawing here: | Repair Guides | Sending Units | Coolant Temperature Sender | AutoZone.com

Last drawing

Make sure you got the right part, but if you said it was for the temp gauge to a Ford parts guy then you would, most auto parts guys wouldn't know what you needed if you just said "for engine temp", ECT Sensor would be first part they would hand you, not the sender

Hottest place on an engine is at the upper radiator hose which is why most temp senders are located there.
And the thermostat.

Your thermostat could be opening too much, spec temp is 192/195 thermostat.
But since sender is at the back of the engine and lower down gauge would be a few degrees cooler than actual temp.

If you want to change the thermostat just to see if that's the problem, then I would wait a bit to make sure there are no coolant leaks

 

I guess I should have stated I did change the T-Stat also when installing the new temp sensor.

Yes it's a 2001 2.5L the sensors I bought was MotorCraft SW5174. It seemed to be working fine for the last week until today when I got her on the interstate and reached speeds of 70-75 which it's never been up to since I got it.

Wayne

 

Currently when driving



Wayne

 

On a 2001 the ECT sender will actually have 2 wires, Red/white stripe and Black/white stripe.

But works the same as a 1 wire sender.
The Black wire is a Ground(threads on sender used to be the ground, so only 1 wire was needed)

The Red wire runs to the dash temp gauge, this is the Ground for the gauge.

So as sender is heated up the gauge gets better ground.

To test if wiring is an issue remove connector on sender.
Turn on the key, gauge should show below COLD, with no connection
Put a jumper in the connector so Red wire is now directly connected to black wire.
Turn on key if you turned it off.
Gauge should now show Full HOT.

If this happens then wiring and gauge are working as they should.

Check connect, if it isn't making a good contact then gauge will drop to COLD