How to fix my factory oil pressure gauge or wire in a mechanical one?

[IH POWER]

Can someone tell me how to fix my old on or to wire in a mechanical? I know where the sending unit is behind the intake. The plug looks to be fine to me. But any ideas on how to get the old one to work? or how to put a mechanical in.

 

[Dave Barbieri]

Are you sure it's your gauge that's bad?

A simple test - Key On Engine Off, disconnect the wire from the sending unit and ground it. If your gauge pegs on the high side, there's nothing wrong with it, you have a bad sender. I'd much rather replace a sender than a gauge. Just a thought....

 

[IH POWER]

Ground the wire or the unit?

 

[IH POWER]

Grounded the wire and the gauge moved up a little bit. So that means I've got a bad sender?

 

[Devon Harley]

buy a new mechanical one.

 

[Dave 001]

Grounded the wire and the gauge moved up a little bit. So that means I've got a bad sender?

No. If you remove the wire from the sender and ground the wiring (make sure to have a good, clean ground) the needle should go off scale high.

If the needle does go off scale high, the wiring and gauge is good and you need a new sending unit (cheap and easy).

If the needle does not go off scale high, the gauge or wiring is bad. Inspect the wiring the best you can. If the wiring looks good, replace the gauge (maybe get one from the junk yard). Since your gauge moved a little bit, your wiring is probably good (the needle did move, just not enough, but there is a connection there) and you need a new gauge.

If the wiring or gauge is bad, a new mechanical gauge starts looking better and better.

Dave

 

[Dave Barbieri]

With the wire touching a good ground (block or cylinder head) the gauge should swing all the way thru its arc to the 'H'. The fact that it only moves a little means you've either got a bad gauge or there's a problem with the wire that connects the sender and the gauge. You can check the wire, but you'll need an ohmmeter (to measure the amount of resistance in the wire) and a wiring diagram. The wiring diagram will tell you which wire goes to your gauge.

1. To check the wire, disconnect the wiring harness from the back of the instrument panel. Touch one probe to the pin in the connector that goes to the gauge and touch the other probe to the end of the wire that goes to the sender. There should be no resistance in the wire. None, nada, zip.

2. Hook the wire back up to the sending unit. Inside the truck, touch one probe to the pressure gauge in the harness connector and the other probe to a good ground. Your meter is now seeing the resistance that the gauge sees. With the engine off, the meter should read 250 ohms of resistance. This is sort of a double check. If your wire has no resistance and the sending unit is showing the right amount of resistance, you've got a bad gauge.

Devon's got a good idea. a mechanical gauge is simple and accurate. I installed one in my truck to back up the electrical dash gauge. I trust it much more than what's in the instrument panel.

 

[Dave Barbieri]

Hey Dave -

You type a lot faster than I do!

 

[GOOSE]

Your factory oil pressure gauge is nothing more than an idiot stick. When the sensor detects 7psi, it closes, telling your gauge to move....somewhere into the "normal" range. THAT IS IT!!! It will not move as pressure increases or decreases. I took my factory lead off and simply grounded it to the block, oil pressure gauge reads in the middle of the "normal" section now.

I went ahead and installed a VDO mechanical oil pressure gauge, electrical coolant temp gauge and a double pod where the ash tray once was. These are right on the shelf at Napa. Sleeve the oil pressure capillary tube with vacuum tubing to straighten it out and give it abrasion resistance. If this little line breaks, you will lose all of your oil. The aftermarket gauges are such a huge difference I can not even describe it. What a peace of mind it is to know what your engine is doing at any exact moment. How many degrees is it when the gauge reads "R" on the "Normal" scale anyway? Cut me a break

Sorry for the rant, I am not trying to look down on anybody, just releasing frustration as to Ford's inability to deliver good gauges. Do yourself a favor, get the aftermarket gauges and don't look back

 

[Dave 001]

it closes, telling your gauge to move....somewhere into the "normal" range.

I forgot all about Ford's "idiot gauges". It does change the gauge diagnosing info above a little bit.

By the way, you are not the only one who dispises Ford's idiot gauges. Somebody at Ford needs to be beat half to death for that one.

Dave

 

[Devon Harley]

I would never trust a factory gauge at all. The waters the same way not good at all. When the light comes on for over heating well it's to late. I added all gauges. In the soon future I'm doing a whole new complete gauge cluster from scratch.

 

[Devon Harley]

Also I have one I could give you pay the shipping can't be much. Light is broken not fixable kind but does work well. Old style but oh well. It's black.

 

[Agnem]

From 87 on up, it is not possible for a temperature gauge to peg on the high side unless the overtemp switch closes. Grounding the wire will result in a mid-range needle position. To make it into a gauge that has more meaning, remove the cluster and then jumper across the resistor soldered onto the back of the cluster. To know which one, just follow the traces from the gauge in question. Then replace your "sender" which is really just a presure switch, with an actual "sender" from an 80-86 truck. Your gauge will function through the entire range. Of course, supliment all your factory gauges with aftermarket ones so you know what the temp and presures really are.

 

[Dave Barbieri]

Mel -

Thanks for pointing out the difference between pre-87 and post-87. That makes a lot more sense out of the "gauge moved up a little bit" result. Starts to sound more and more like a bad sending unit.

 

[IH POWER]

Put in a new sending unit and works like a champ.