Oil and Temp Guages

[Ramblinwilly]

Neither the oil or temp gauges were working when I purchased the vehicle. For obvious reasons I checked fuses then the oil pressure first. All is good there. Everything sounds good with no unexpected noise from motor. The temp gauge never moves. Never overheats and I've taken it on 250 mile trip with no issues.

I'm going to replace the oil pressure switch and the temperature sensor first and see where that gets me. If that doesn't fix both gauges, I need a plan B. Plan B seems to be the dash unless anyone has any ideas. I've removed a number of dashes from older f150's but don't see how to remove it from my 91 Ranger. Is there anyone that can give some guidance on the dash removal or have any other suggestions?
Thanks.
Willy

 

[malohnes]

I'd double check the connectors to the sending units. My oil pressure gauge sometimes acts goofy because the connector is not making good contact and the coolant gauge wasn't working due to a crimped wire near the sender. A new connector cured that issue.

The coolant sensor is a one wire unit near the water pump outlet, the two wire sensor nearby is for the CPU. They're relatively easy to get to and swap out if the wiring is healthy. The oil pressure unit is a pain, but is most easily accessed by removing the inner fender not he driver side. You can get to it from the bottom, but I needed a better angle and that came from the fender well.

 

[arco777]

The coolant temp sender for the gauge can be pretty easily checked with a multimeter, it is just a varying resistance value. With the engine cold and coolant at ambient temp, check the resistance of the temp sender (shouldn't have to remove it). Check the resistance against the temp values on this page - http://oldfuelinjection.com/?p=28... Note that while the page I linked to shows the 2-wire coolant temperature sensor, the single wire coolant temp sender should have similar resistance values. The sender feeds the gauge, the sensor feeds the PCM.

If the sender checks out, pull the gauge cluster. Just remove the dash bezel. There are two screws behind the ashtray once you pull the ashtray out. I think that is all of them... then carefully pull the bezel off and try not to break off any of the push-in fasteners. Being a 91, your bezel probably has the option switches mounted separately from it, which makes removal easier. Once that is all removed you will see the cluster, mounted up. Instead of removing the whole cluster, it's much easier to simply remove the clear faceplate, then the black plastic shroud. You'll notice the cluster is divided into sections; one for the speedometer, one for the tach (if equipped), one or two for other gauges depending on options. Then you can pull out the chunk of the cluster that has the temp gauge (it may have oil pressure gauge there as well). It simply pulls out; the gauge contacts push into slots when it's re-installed. Once you have pulled out the "chunk" that has the gauge in question, you can probe the contacts in the cluster housing with a multimeter to see if the coolant temp sender's resistance value has made it all the way to the cluster. If it has, you can look at the gauge itself for damage, and even stimulate it with 12v/GND/resistor to simulate inputs and see if it moves. The process is very similar for testing and troubleshooting the oil pressure gauge!

 

[Ramblinwilly]

Thanks for both responses. I'll be doing the "checks" and potential dash removal when weather gets a bit better. I'll surely post pictures during all the work for a sticky.
Thanks
Willy

 

[malohnes]

Arco has it correct, as I tend to call sensors and senders the same thing. They in fact are not the same.

 

[Ramblinwilly]

Yup....My neighbor yells at me all the time for calling a sensor a sender and a timing belt a timing chain. As long as we know what it is and what it's supposed do, we're good to go...

Thanks for the help..
Willy