I have the full digital cluster in my car and I am having an issue
I changed the sending unit to the larger gauge type (bell shaped) with the extension in the block, it had the smaller type that is usually used for idiot lights .
Yesterday I had the car running for a little while and the gauge started blinking and the warning chime started going off .
I shut the car off and hooked up my mechanical gauge and I had about 23 lbs at idle , which I always thought was adequate .
I'm assuming the sender is malfunctioning and reading too low , but I'm not sure
Does anyone know at what pressure the chime is supposed to start chiming ?
I had no issues before the change ,I just thought the gauge would be more accurate with the larger sender , seeing as how the old one is basically an on off switch.
The new sender was a BWD S334 listed for a Mustang with a gauge if it makes any difference .
Have you tried swapping the old sender (given you still have it) back in to see what happens?
I did it operates exactly like it did before
I have 5 bars showing at all times while the car is running .
SSome of the large ones are still idiot lights. they are idiot switches with a built in resistor. You have a a resistor in line. The only true one i have found is from napa. Pn ps-60. See here. http://www.sccoa.com/articles/oilgauge.php you will know a real one when you hold it. Weighs 4x. Costs 3x.
With the old switch or the new?
I'm not very educated on exactly how these switches work (among a lot of other things as you know ;) ) but maybe the bigger switch is meant for higher pressure readings (maybe not much higher) and has a different "range" than the stock switch, which I would think would send inaccurate pressure readings to the cluster?? I don't know, really, just a thought.
The original switch is 5 bars all the time , the "bigger" switch was 4 at idle 5 bat 1500 rpm and above ..except when the car got warm ..it dropped to 2 bars and the chime went off .
The BWD S-334 cross references to the PS-60 ......so I'm thinkin maybe I got a bad BWD switch .. I'm trying to find out the range for the one I have.
Seems like the switches may have different resistances, or as you said, you got a bad switch.
O'reilly has a warranty so I think I'm going to exchange it anyway .
That may be true but it may still be a switch. The one Autozone has crosses as well, but I assure you, its a switch with a resistor inside. I opened it up after I crushed it (on my first attempt). The ECH OP6091 is the only one I can personally vouch for. Napa carries them, for a 74 bronco 351w. Maybe yours is just faulty.
Is there a little resistor pack inline with your harness? Usually its a barrel plug that goes into a little brick with harness tape then to a wire and the sender cap. If so, you need to pull that off.
Some background story:
When Ford used to install real senders, people understood that oil pressure varied with RPM. Sometime in the late 70s, they introduced their first oil warning system that would chime when oil pressure dropped below a certain level. People freaked out when on hot days in traffic, with the trans in gear the oil pressure would sometimes drop low enough to trigger the alarm. So the engineers at ford "fixed" it. They made an oil pressure sender that looked like a real sender. Inside was a switch and a resistor. The switch triggered at some PSI and the resistor put the gauge in the middle of the range. People stopped complaining.
A few years later, they incorporated a short resistor retrofit cable that attached inline with the sensor wire (brick mentioned above). This let ford install a standard switch (small body) on the engine and still have the gauge read perfectly in the NORM range.
By the time the MN12 was designed, they incorporate the resistor into the back of the instrument cluster. I had to bypass this resistor to get mine to work correctly in my supercoupe.
If you still have the resistor inline, the gauge will read low all the time. On my 88, i had the little brick wire. I simply disconnected the brick and connected the sender wire directly to the sender.
-Dan
My car does have the add on resistor in the harness, ( the brick) I unplugged it when I put the larger switch in .
I'm going to swap out this switch and see what happens if I get the same result I'll make a trip to NAPA.
Thanks for the info ,
Do you happen to have any pics of the inside of the switch you opened ?
Sorry, I don't. I was kinda peeved at it after I crushed it by accident and couldn't return it. I don't think I kept it, but I will check later today in my junk drawer.
Dan, thanks for sharing that. It makes sense.
Now I know what that little brick is.