Stock oil gauge v. stock idiot light v. mechanical gauge
 

On another thread (https://www.ford-trucks.com/forums/9...gets-warm.html) there is a discussion about oil pressure, and the topic of stock oil gauge reliability comes up.

Like many of us, I've got a stock gauge. Oil pressure might be the only thing in the world I'd prefer an idiot light for, because the light might get my attention better than a gauge in the 10 seconds or so you've got to shutdown in the event of a catastrophic loss of oil pressure.

All of that said... what's better? I'm sure an aftermarket gauge is better than the OE, but how reliable is an idiot light? Does anyone make a mechanical (or electrical, for that matter) oil gauge with a built in idiot light? That seems like nirvana.

And for those with aftermarket gauges already installed, what are good baseline numbers for oil pressure PSI in the different engines?

I feel the same way--in a given, six hour (night time) drive, I'm sure I'd be embarrassed by how few times I look at the oil pressure gauge. A combo (real) gauge and idiot light would be perfect.

Excellent questions--Subscribed!

well, your stock oil pressure gauge really is an idiot light. the stock sender is only an on off switch. so it either has pressure or it don't.
the gauge is just there to look pretty in the dash.

No, the stock gauge is not "an idiot light," for several reasons, the first being that it's not a "light." The OP is interested in having a visual warning, (i.e., a suddenly-illuminated light) to indicate catastrophic pressure loss, instead of having to stare at the fake "gauge" every few seconds. The OP is saying he wants a light to alert him to look at the guage--and preferably, an actual gauge, instead of the stock on/off" indicator (fake gauge) you correctly describe.

On the Chevys they had both real gauges (temp and oil with real units for both) AND a light that said something like "LOOK AT TEH @!#%%! GAUGES!!" when any of them read high.

yes they make them... We use VR's in the figure 8 cars out here... You can set them to the limit you want so the warning light will illuminate when the oil pressure drops below the limit you set it at...
VR Speed Factory - EVO, DSM & WRX Performance Parts - 52mm Premium Peak/Warning Gauges - Prosport Premium 52mm Oil Pressure Peak / Warning Gauge

Cyberdyne also makes some that we have used but it wont match the interior as well...
Tognotti's Auto / Truck / Import World

AutoMeter also makes a good guage and I think some of them come with a red LED warning light... You'd have to call and ask someone or look up each meter online to see what each does...
AutoMeter Ultra-Lite Gauges - Autometer Speedometer, Autometer Tachometer, Vacuum, Water Temperature & Autometer Boost Ultra-Lite Gauges

OP Guage with an idiot light is not a new concept... They are already out there. You just have to go find one you like and install it.

That's the same company that manufactured the Terminator... I don't know if I'd trust them. :D

How about the following:

1) you take your gauge cluster apart, locate the resistor behind the oil pressure gauge and remove/jump it, then install an oil pressure sender for an '80s truck (they had real gauges) at a convenient location on the engine.

2) you splice the wires off the factory oil pressure switch into the wires for the coolant temperature switch that triggers the red engine light.

You get both a decent gauge and a warning light for the price of an oil pressure sender and a few hours of wiring if you take your sweet time.

I personally hate wiring... it's not that hard and I've done it before but i'd rather not mess with my OEM wiring (knowing myself i'd mess something up)... But yes that would work too and wouldn't cost as much if you like playing with your wires...

The only problem with that wiring set up is that you'd have to wait for the engine to become hot enough to trip the engine light... And by that time you might already have engine troubles... I thought the point of the OP guage was to give and immediate warning light to the driver of low OP...???

Thanks everyone.

I don't think I'd care to delve into rewiring the factory gauge cluster. I'm looking to prevent problems, not cause them. I'll have to have a look at those gauges nstueve mentioned. I figured someone had thought of the idea (and after mprice mentioned it, I also recall the "Check Gauges" light in some GMs); hence I asked.

Also and again - once I get a real gauge, what should the pressure read in the 300 EFI?

All makes of vehicles should have a combination of warning lights AND gauges!

Why manufacturers will spend money on cup holders and fog lights and NOT have warning lights and guages to protect your investment in your vehicle-I cant understand!

I plan on putting the one from VR in my ride depending on size and what not. I will be buying a idiot light and OP guage in one... Just in case any friends borrow my truck...

oil pressure varies with different conditions even for the same motor.

It sure does, 75 psi or so at start up, 25 psi or so at idle, 50 psi on the throttle. Psi always fluctuates. Shouldnʻt it?
Add a real gauge, all my trucks have them.

Ok, there's some confusion on how the oil gauge on the 80 to 86 trucks operates.

These year trucks are true gauges that should show aprox oil pressure, Ford did the "idiot gauge" starting in 88. Now if you happen to use a 88 and up oil sending unit on the 86 and below, the gauge will not read and stay low. I know as some part's monkey gave me the wrong sending unit for my 84 F250 and after "making a point" got the correct one.

The 20 ohm resistor bypass is only for the 88 and up trucks and use the on/off type sending unit. I think it opens at 4 to 10 PSI and that makes the gauge show low.


You can make up a "low oil pressure" indicator by using a correct sending unit tee'd in with the original sending unit. I also though about making a buzzer activate with the indicator so I can see and hear a problem before a worse noise happens!

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 :-X09