89 Rx7 temp and oil pressure gauge problem
 

Hey guys! I recently pulled the engine out of my 89 n/a to fix a major front cover leak it had for a little while. So we dropped the engine back in yesterday, got everything hooked up and ready to go. And now my temperature gauge doesn't work and my oil pressure gauge maxes out as soon as I turn the key on to accessories. I have the correct wires going where they need to go. Any ideas? Greatly appreciate any help given. Thanks.

Are you positive the water temp sensor and oil pressure sender are connected correctly? If the pressure sender wire (Y/R if I recall correctly) is grounded against the chassis, the gauge will peg. It will also damage the gauge if you allow it to do so for very long. The circuit needs a small amount of resistance, which is normally provided by the sender.

The water temp sensor get the yellow(?) wire with a bullet connector.

Yes sir. The sensors functioned properly before the engine was removed and they were left alone and not touched till I started connecting everything. Only thing I can think of is there is a break in the wire going to the temp sensor or the sensor is bad. And the sending unit may be faulty or there is oil on the plug.

http://www.rotaryheads.com/PDF/2nd_g...stem_part1.pdf

Pg. 15-30 under "Meters"

If you have a resistor in the 100-200 ohm range, you can temporarily connect it to the end of the oil pressure sender. Ground the other side to the chassis. You should see the needle on the gauge move part of the way up relative to the resistance.

30 psi - 197 ohms
60 psi - 141 ohms
110 psi - 103 ohms

For the sender, if the engine is idling, you can measure resistance of the sender. You'll have oil pressure, so there should be a value somewhere around 200 ohms.

For the water temp sensor, check page 15-32. The temp sensor itself can be tested in a pot of boiling water, but you'll need to partially drain the coolant before removal. You can also warm the engine up and measure the resistance between the sensor and a ground point.

For the gauge, you can use the resistor trick from above. The two temp/resistance values in the FSM are:

50C - 154 ohms
130C - 12 ohms

I found and fixed the problem. I feel like I wasted your time. The wire that connects to the sending unit had a non factory plug and the previous owner clamped it down on the colored part of the wire do that the only thing making contact would be the small amount of wires coming out of the outer layer and wasn't making contact properly. The temperature sensor wire (I just figured out that wire comes from the passenger side harness) was connected to the wrong thing. On the S5 Rx7's there is a small black relay that mounts to the same hole the clutch slave bolts to and I had that plugged in to the temperature sensor wire. And visa versa. But the temp sens wire was too short so I had to lengthen it to reach the sensor.

The black thing is a condenser for the oil pressure gauge. It supposedly smooths out the signal, but they're missing from most 2nd gens by now. It sounds like someone did a hack job with some of the wiring. Hopefully the rest of it is in better shape.

Lol yeah. There's more than a fare share of vacuum lines and plugs either blocked off or not a partner plug for it. But none of it affects the way the car drives. I guess it was done for the better.. But Thank you and I appreciate your help and time.

Oil Temp Gauge, Requesting some Guidance.
 

My needle is pegged and the Y/R wire is grounded somewhere. My question is this, can I just replace the wire from the oil pressure sender to be wired directly to the gauge/cluster of ME-02 PIN #6.

Would this work?

I just don't want to remove the harness that includes the Y/R wire for the oil pressure sender. Any ideas or help would be great. Thanks.

I gather you could do that, but the gauge will be damaged if the needle is pegged too long. Also, the wire running to the condensor might not be connected to the condensor, but itself grounded to something. An ohm meter will tell you where the grounding is occuring. The wire from the sender unit runs to a couple of different connectors before arriving at the gauge so each wire segment involved is rather short in nature. Looking at the wiring diagram will tell which connectors are involved in addition to their respective locations.

Hardwired from the oil pressure sender directly to the back of the gauge cluster PIN #6 and it works! Fixed the gripe and buttoned everything back up. Easy Fix vise trying to look for a break or ground on the Y/R wire. Took only 15 or so minutes.