Oil pressure gauge /sending unit question
 

My oil pressure gauge has not worked in over 2 years, so I thought I would fix it. I put on a new oil sending unit from my other car (it was only about a year old on the previous car). However, I still read 0 pressure. I checked the new sending unit and I get these numbers:

140 Ohmns at idle
119 Ohmns at 2000
124 Ohmns at 3000
123 Ohmns at 4000

Moy old unit is like this:

47 Ohmns idle
47 Ohmns 2000
47 Ohmns 3000

Both units are disconnect when car is off. I measured the dash guage between the sending wire and the block and get 48.7 Ohmns engine off. Ignition on I get 12.3 Ohmns.

So, I am getting voltage across the guage. And some type of resistance from my sending unit. I looked up the schematic in my Haynes and it shows the sending unit as a pot in series with the gauge. So as the sending unit varies, the current is changed across both resistors.

My question is this, does anyone know the correct sending unit resistance or range. If I can get this, I can hook up a resistor and know for sure what's going on.

Thanks

I replaced mine new from Mazda now it works properly.
Spent about $80.00
I was going to to the same test as you but ran out of time and patients so I broked down and shelled out the money.

Good Luck

The one I put in is only about 3 years old and was only driven for about 4 months before the car got wrecked, so it should work. I am trying to determine whether the problem is in the sending unit or the dash.

Since I am getting a resistance out of the unit I would assume that my gauge should work. I wouldn't assume that 150 ohmns should be outta wack too much since my static inductor resistance from the gauge reads around 45 ohmns.

I have another dash cluster. I'll try hooking the 12 volt and the sending unit ground up in the engine bay and see what happens.

If worse comes to worse, out goes my clock and in goes an oil pressure gauge :).

I was reading through the threads and someone said to check it, disconnect the sending unit wire and the guage should read full. This is not true. After examining the circuit, disconnecting the wire will make an incomplete circuit and the gauge will read zero.

Just for FYI, the circuit indicates that both the tachometer and the oil pressure gauge both share the same 12v node. So, if your tach is working, then your getting power.

So, anyways, where's my specs guys?

Err and girls, no offense intended.

I think if you just ground out the sending unit wire, the gauge should move if it works...Am I right or not?

~T.J.

I would think it should move on ground, but it doesn't. The problem is, when the car is running, I cannot measure any resistance over the gauge. With the car off I can measure around 45 to 50 Ohmns. So I am not sure if the device will move on ground.

If someone can try it and let me know I'd appreciate it. Or maybe see what the Chilton's manual says or the factory repair manual. My Haynes sucks so bad, they don't even acknowledge that I have air conditioning.