actualy it started in 87 with the new body style, not 88

 

My '87 has a variable resistance oil pressure sender, as did an '88 truck I snagged a wiring harness from. I always thought '89 was the first year for the "dummy gauges" since there were some changes in the wiring that year as well.

 

No you don't - the sensors for the coolant temperature and oil pressure are wired in parallel, so they can each ground the circuit and trigger the light on the dash independently of the other sensor. Basically when the light comes on you'll have to look at both the coolant temp and oil pressure gauges to see which one is pegged, but the purpose of grabbing the driver's attention is met.

 

So the oil temp gauge is really an 'idiot gauge?' Why bother then? The water temp, voltage and fuel gauges really work.

 

There's no oil temperature gauge, you have coolant temperature which works like it should, and oil pressure gauge which is an idiot gauge.

 

Er, right, oil pressure. Typo.

 

Depending on what options you have you may have just an idiot light. My truck like many have an oil pressure gauge that is variable. I know this because when I replaced the sender the guy at Advanced Auto gave me the idiot light sender when I needed the actual variable one, so I had to make the trip back down to return it and go to NAPA, pain in the butt. I do also believe that if you have the variable one like most do, and it drops low the check engine light will come on.

 

I wish!!!

I don't think that most 93 vintage F series have a factory variable oil pressure sender. I suspect that you truck got converted in the past by a PO.

 

If its a gauge that looks like the temperature gauge its variable, if its square and says oil pressure on it and lights up in RED its not. Not conversion, Factory when you go to a NAPA and the guy reads his computer he will ask you if it has a variable pressure gauge, if you put the idiot light oil pressure switch in, the variable guage will stay at 0

 

Not true. The factory "gauge" uses an off or on sensor . It will read in the middle of the gauge if the oil pressure is 6PSI or more. If less than 6PSI---it will read no oil pressure. There is a resistor factory wired to the back of the gauge to make sure that it always reads in the middle and that the needle doesnt change when the temperature of the oil changes and when the RPM changes. The needle on a factory setup for your vintage will never have the needle move at all-if the oil pressure is 6 PSI or more.

Take a look at your factory oil pressure gauge. Does the needle ever move when the engine is running?? If so-it has been modified. I have been told that if a variable sender from an earlier F series is added-and the factory resistor isnt removed-the gauge will become variable-but only for the first half of the gauge range---not the full range of the gauge. Because the resistor limits the full range of the needle.

I checked www.napaonline.com and noted that NAPA calls it a switch-not a sender. For our vintage F series.

This oil pressure "gauge" for this vintage F series is one of the most sucky things that Ford has done .Why would Ford cheap out on something as important as an oil pressure gauge?

My Jeeps have real electronic oil pressure guages from the factory and you can see the needle move as the oil warms up and when the RPM changes. And the Jeep gauge is graduated in PSI.

 

It's my understanding that it was not due to costs, but due to a high number of dealership visits with complains of the gauge reading on the low side (mostly with the 302 and 351 engines) - so instead of fixing the low pressure issue (which isn't much of an issue to begin with) by modifying the pumps, Ford took the easy way out and just covered it up with that switch and resistor bull. Yes, very sneaky and totally unprofessional, but that's the big corporate world for ya