SublimeMudTime
Member
- 171
- 5
- 18
- Location
- Chaska, MN
So I was having an issue with my oil pressure reading fine at some times and then it would go into a spike mode where it would bounce up to 90psi or all the way to the max.
I posed the issue to my mechanic and he said it's gotta be the pressure sensor/sender.
Rather than following the TM troubleshooting flow chart I went and ordered a new sender unit.
Yesterday I went to the shop where the truck is and popped the doghouse to pull the old sender. I grabbed the wiring and on the sending unit the rubber shell and a tiny nut and plastic washer just came off.
Turns out the nut holding the rubber shell on the sender had backed off causing an intermittent connection. So I did a test of making the connection and firing the truck up. The gauge worked fine. So I pulled the wire from the sending unit and saw the gauge go to the max.
UGH! Who would have thought that the sender unit acts as a variable pull down resistor. And for those who do not know what a pull down resistor is, here is a good explanation: http://playground.arduino.cc/CommonTopics/PullUpDownResistor
So for all the rest of us new HMMWV owners I have some advice to repeat that others have stated here: READ THE TMs to save everyone's time and some cash. Stop looking for a quick fix or make assumptions that these things are just like a normal vehicle. Had I done that, I would not be sitting on a NOS spare pressure sending unit.
I posed the issue to my mechanic and he said it's gotta be the pressure sensor/sender.
Rather than following the TM troubleshooting flow chart I went and ordered a new sender unit.
Yesterday I went to the shop where the truck is and popped the doghouse to pull the old sender. I grabbed the wiring and on the sending unit the rubber shell and a tiny nut and plastic washer just came off.
Turns out the nut holding the rubber shell on the sender had backed off causing an intermittent connection. So I did a test of making the connection and firing the truck up. The gauge worked fine. So I pulled the wire from the sending unit and saw the gauge go to the max.
UGH! Who would have thought that the sender unit acts as a variable pull down resistor. And for those who do not know what a pull down resistor is, here is a good explanation: http://playground.arduino.cc/CommonTopics/PullUpDownResistor
So for all the rest of us new HMMWV owners I have some advice to repeat that others have stated here: READ THE TMs to save everyone's time and some cash. Stop looking for a quick fix or make assumptions that these things are just like a normal vehicle. Had I done that, I would not be sitting on a NOS spare pressure sending unit.
