Light switch & removing instrument panel

[jingo]

I've got to remedy a fair number of annoying electrical issues with my truck - dome light, backup lights, courtesy lights, turn signal return, brake lamp, no horn, etc. Also the PO installed new voltage, oil pressure, water temp gauges under dash...and a tach, which only works above 1000 rpm, otherwise bounces then drops to zero. None of the original gauges are working.

Armed with an ammeter, alligator clips, and the very helpful wiring schematics on the forum, I'm determined to fix this stuff. I'm looking for some advice on a couple of points...or any other suggestions that will help me work these fixes properly.

First, I'm thinking the light switch is a good place to start, pretty straightforward for a beginner and a known issue generally. My courtesy and dome lamps flicker occasionally but otherwise don't work, so the switch is an issue. I'd also like to wire door switches to this circuit. Is this really a good place to start, and where can I scavenge a couple of door switches that would (hopefully) be an easy install and work for me?

Second, with the mass of factory standard and secondary wiring present, it would be nice to remove the dash cluster for additional access, e.g. not ALWAYS on my back! If I disconnect the connectors from the cluster, can I still drive the truck? Since none of the gauges are working, it's no big deal to me. But I don't know what critical circuits, if any, might die if I pull the cluster and I leave it out (temporarily).

Thanks!

[sargentrs]

I'm by no means an electrical expert but I believe you can unplug the cluster and still drive your truck. Should probably put a piece of electrical tape over the open circuits on the harness plug. There's a terminal there that is a constant/switched hot (wire 904 to the voltage regulator) and you don't want something accidently touching it to ground.

[jingo]

Thanks, good thought on the cluster plug.

Any thoughts on working my way out from the light switch? For instance, I see a lot of switches for sale, are any better made than others, not junk that will fail again on me?

[sargentrs]

Any thoughts on working my way out from the light switch? For instance, I see a lot of switches for sale, are any better made than others, not junk that will fail again on me?

These days when you're talking about electrical components, especially those with mechanical functions like a headlight switch, it's a crap shoot on quality. Stick with name brands like Borg Warner or Standard Motor Products and hope for the best. Not sure why, as they have the same brand, but NAPA seems to have higher quality parts that AZ, Advance or O''Reillys. Just my opinion, of course.

[mulletmobile]

Just one thing I discovered with my truck while working on wiring and cleaning the inside of the cluster and lense, it will not start with the gauges disconnected. Not sure the exact why, but it will not without them in there.

[Redcrew71]

did you make any progress on back up lights and signal lights? dont have back ups myself and signals work but fast on the left side and when hazzards some times they work but fast.

[jingo]

No, afraid not, im working on restoring the front end, body work, rustproofing panels, inner fenders, core support, reworking aluminum trim, etc. trying to get it all ready for paint and reassembly, hopefully by the end of the week.

[Thipdar]

#1 - What's the year, make and model?
#2 - Which engine are you talking about?
#3 - Does your instrument Cluster use indicator lights or does it have gauges?

(For 1970) There are three ways to turn on your Courtesy Lamp: opening either door closes that door's Courtesy Lamp Switch, the remaining way is to rotate the Headlight Switch all the way clockwise. This circuit gets power from the same fuse that provides power for the Cigar Lighter. Intermittent operation of the Courtesy Lamp would most likely be from one of the switches (either at one of the doors or in the Headlight Switch).

Engine failing to start when gauges are removed makes me think that the Oil Pressure Sender is disconnected. Engines aren't supposed to start if they can't tell if there's any oil pressure. It would be suicidal for the engine to try and run with no oil pressure. The Oil Pressure Switch applies ground to turn on the Oil Pressure Indicator Light, the Oil Pressure Sender applies a variable ground to provide a signal to the Oil Pressure Gauge.

[jingo]

1970 Ranger LWB

In my case the door switches are absent. The 2 pin connectors hang free in the access for the lower hinge. Question: what standard door switch can I install? I’m guessing there’s a cheap and easy bolt in, but I don’t know what P/N or where to get them.

I bought a new light switch assuming it is faulty, and also because it is a frequent point of failure on multiple lighting circuits. Taking the switch out of the equation for $25 will save me alot of time troubleshooting my lighting issues. Question: is the dome light part of the courtesy lighting circuit? I think it may be.

The Ranger dash cluster included gauges, not indicator lights, in all four cluster positions. However, the PO installed a set of secondary analog gauges below the dash, including oil pressure (+engine temp, ammeter, tach). All of these gauges appear to function properly, and I’m guessing the easiest way to do this for the oil pressure is to bypass the dash cluster, since none of the original gauges are functional. Question: is it possible to have both the new gauges and the original ones operate in tandem, e.g. can the oil pressure, coolant temp, and ammeter ‘senders’ provide signal to two gauges simultaneously? I kind of like the idea of redundancy for the old gauges, especially since there’re already installed.

[DisneysPatB]

1970 Ranger LWB

In my case the door switches are absent. The 2 pin connectors hang free in the access for the lower hinge. Question: what standard door switch can I install? I’m guessing there’s a cheap and easy bolt in, but I don’t know what P/N or where to get them.

I replaced mine DS163 Standard.

[DisneysPatB]

Engine failing to start when gauges are removed makes me think that the Oil Pressure Sender is disconnected. Engines aren't supposed to start if they can't tell if there's any oil pressure. It would be suicidal for the engine to try and run with no oil pressure. The Oil Pressure Switch applies ground to turn on the Oil Pressure Indicator Light, the Oil Pressure Sender applies a variable ground to provide a signal to the Oil Pressure Gauge.

I did not know this. Very good info.

[1guydude]

im pretty sure I started my truck. Even drove it with no instrument panel in. or working. I did have dummy oil and temp gauge though that I threw in the slot where the radio should b.

As far as the parts go, I do a lot of ebay or rockauto. However if needed u can shop at Dennis carpenter, LMC, or macs auto. They should have everything u need or could want for these old trucks.

Im waiting on my dome light but will be doing mine here soon and yes id like the courtesy light and dash lights to work as well, I will report back when my part comes in.

What motor are u working with? Mines a 67' with 390 motor

[jingo]

Thanks Disney, that was easy! Wish there were straps still mounted to receive the switches, but they’re long gone. : The only ones to be had are installed in someone’s driveway, or a field somewhere. If anyone out there has said field and could spair a couple of door switch brackets, that would be cool, please PM. Otherwise, there’s a sketch to fab one posted on the another site. I’m afraid that’s what I’m left with. Unless anyone here has a better idea.

[Thipdar]

Engine failing to start when gauges are removed makes me think that the Oil Pressure Sender is disconnected. Engines aren't supposed to start if they can't tell if there's any oil pressure. It would be suicidal for the engine to try and run with no oil pressure. The Oil Pressure Switch applies ground to turn on the Oil Pressure Indicator Light, the Oil Pressure Sender applies a variable ground to provide a signal to the Oil Pressure Gauge.

I did not know this. Very good info.

I'm having second thoughts here. I can't see how the Oil Pressure signal acts as any kind of a safety interlock on the ignition process. I was probably thinking of the '76 Pontiac Sunbird I once owned.

[Thipdar]

Thanks Disney, that was easy! Wish there were straps still mounted to receive the switches, but they’re long gone. : The only ones to be had are installed in someone’s driveway, or a field somewhere. If anyone out there has said field and could spair a couple of door switch brackets, that would be cool, please PM. Otherwise, there’s a sketch to fab one posted on the another site. I’m afraid that’s what I’m left with. Unless anyone here has a better idea.

If you are referring to the brackets that hold the Courtesy Light Switches on the door jamb, the Ford part for 1964/72 F100-750 is C7TZ-13B756-A. The basic part number for the screws that hold it into the door jamb is 52726-S2. The part number for the switch itself is C8AZ-13713-C.

(Edit: The PN for the switch may have been updated to C8OZ-13713-C (Motorcraft SW-659), so try that too)

Check the Dennis Carpenter catalog.

By the way... DO NOT put a Courtesy Light Switch into the mounting bracket and then close the door WITHOUT CONNECTING THE CONNECTOR! The pressure from the door will make the switch come apart if it's not held together by the connector shell. The various pieces of the switch will fall into inaccessible parts of the fender well, and you will have an EX-SWITCH. Don't ask me how I know this