99 Ranger XLT 4 liter temp sender malfunction

[tom2rn]

I recently replaced the t stat and temp sender. Used Motorcraft t stat. Now my gauge in the instrument cluster doesn't work at all. I grounded the red/white wire and the gauge went all the way to hot. So, there is integrity to that point. I did replace the new sensor with the old one and same result (it wasn't bad, I replaced it as maintenance). Everything was fine until I messed with this. Would it be the pcm or cluster? I receive different answers. Unfortunately, I don't have a scanner with bi-directional control. I can read the temp with my standard scanner, so I know the temp sensor is correct. Help!

 

[RonD]

Welcome to TRS

Computer(PCM) is not involve, its a 12 volt Sender, not a 5 volt Sensor, just FYI

If there is a black/white wire with the red/white wire then black/white wire is the Ground for the circuit
These Temp senders used their threads for the ground, since the 1930's, but as more and more plastic parts were being used on engines some Temp senders were changed to 2 wire and have a ground wire

If you have a 2 wire plug for the temp sender then do the same test, for red/white wire, but ground it to the black/white wire,, i.e. just jumper the 2 wires together
If gauge doesn't go to HOT then black/white wire is broken, not grounded

If you just have a 1 wire temp sender connector then make sure the lower threads on sender are bare metal, NO TAPE, so they can ground to the metal of the engine

 

[tom2rn]

One wire system. Threads are bare metal. I even grounded the brass part of the sender to the battery negative.

 

[RonD]

There is nothing else to the circuit

Cluster(12v)----Temp gauge-------------(red/white wire)------------------Sender/ground

Re-test red/white wire but ground to engine metal, see if you still get the gauge to HOT

And the Senders you have only have the one connection on the top, not 2 for a 2nd wire

 

[tom2rn]

I grounded to battery negative, a body ground, and engine ground. Gauge went to hot in each circumstance. Insteresting thing, it read 9.2 volts each time. My sensor has two pins (even the original). The wire is red/white.

 

[RonD]

No real reason for it???

If old one wasn't working and new one was bad out of the box(happens ALOT now) then that would explain it

If you have an OHM meter you could test each contact, of the two, to metal case on sender, one should be 0 ohms, the ground terminal
One should be 80-100 ohms cold/"room temp"

But if you reversed connector gauge should just go to HOT, same as grounding it

 

[tom2rn]

I tested the old sender which is back in the truck. Black lead to case and red lead to each of the terminals. No resistance on both pins. I took the new Carquest one I had previously put in the truck the other day and 0 on one terminal and 19 ohms on the other. Ambient temp is 70 degrees. No good on both accounts. Must be a bad one right out of the box since it doesn't meet the minimal 80 ohms.

 

[RonD]

But odd thing is the 19 ohms SHOULD show above 1/2 on the gauge when plugged in

 

[tom2rn]

I'm stumped. All I did was unplug this sensor and put a new one in. I put the old one back in when the new one didn't work. Would it be any better if I got the Motorcraft one? I hate to be a parts cannon person.

 

[RonD]

Well assuming old one was Motorcraft, and original, then it lasted 20 years so might be good to try one

 

[tom2rn]

Will give it a try.

 

[tom2rn]

Bought the Motorcraft sender this morning. I'll put it in after work later today. Here's hoping it works. I'll probably check the continuity before I screw it in.

 

[RonD]

Just to double check
12volt Temp sender will have a cylinder shaped end, like this: https://image.shutterstock.com/image-photo/spare-part-excavator-called-coolant-260nw-1076578271.jpg

5volt Temp sensor will have a cone shaped end, like this: https://i.ebayimg.com/images/g/H8cAAOSwhTBbFOQ1/s-l500.jpg

 

[tom2rn]

Good news. It works. I bought the Motorcraft sender and put it in. Ran her up to operating temp and she's around 194 to 198. T stat is 192. Thanks for the above tip about the different shaped ends. I did not know this. I'm no mechanic, just have some common sense. I still want to put in one of the 2" or 2 1/16" style gauges on my A pillar for a tach since this truck does not have one. I've seen VDO, Bosch, GlowShift, Autometer and Sunpro gauges. Any recommendations there? Something decent, but not overspend the truck. I like GlowShift because of features, but reviews are so so. I personally take the top 10% and low 10% comments and throw them out. Why? The top 10% usually try to blow sunshine up your butt and the low 10% are usually because they did something wrong in installation. Thanks for the help. I've learned a little something.

 

[RonD]

Good work

All Rangers since around 1989 are pre-wired for a tach, so wire is there whether you have a tach or not

And 1996 thru 2003 Ranger clusters are interchangeable, plug and play
So you could just install a cluster that has a tach if you want

Black face or later model white face as well