1979 F350 400 4speed

I have been having electrical issues lately. Most days I have no blinkers. Some days I have a right blinker. Rarely do I get both. I almost never have dash lights...actually I can count the time in minutes that I've had dash lights. I have checked fuses. Thats as far as I've gotten. I would like some guidance or a list to run down before I just tear into it. Thank you in advance for your reply.

 

Could be as simple as a ground. Check all grounds in and around your dash as well as the grounds at your headlights/taillights. This is the easiest thing to start with.

 

Ah,
__these old trucks can fustrate.

1.Start by pulling batt. neg. cable.

2.Go to fuse box pull 1 fuse at time
& with a good light; look to see if the
fuse contacts are rusty. If so; clean.

3.Check/clean all grounds.

4.Check bulb sockets for any rust
or faulty wiring. Clean gauge cluster
contacts as well.

5.Check/replace all bulbs.
If doubtful that bulb is working; replace.

6.Remove dead-end's, add-on's, &
that-will-do's. That are usually in these
trucks from past owners. Clean up the
wire harness. So you will be the one that
knows where what wire go's where.

As, if this isn't enuff info; here.
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Odd Electrical Behavior, Blinking Lights, Dim bulbs, Flashing Lights, Bad Gauges etc.
By: Torque1st
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For many of the crazy electrical problems on these old trucks the problem can be traced to bad grounds. Remember it takes a complete circuit in order for electricity to flow. A bulb or socket may no longer be grounded due to corrosion. An entire fender may not be grounded due to rust. Check the body and frame ground points and cables, Many aftermarket battery cables do not have a ground tab on them that was used to ground the body and frame like the OEM cables did. Clean all connections to bare metal and coat them with silicone dielectric grease. Use internal or external tooth lockwashers as appropriate to help maintain electrical contact. The lockwasher provides a little "spring" to the connection that will help maintain electrical contact during heat/cool cycles. Make sure the body panels, cab, frame, and engine are grounded.

A battery cable that looks good can have corrosion between the cable wire strands and the terminal body. I have been making all of my old battery cables from those lead free terminals and welding cable or standard battery cables. I cut the factory ends off cables and make my own connections. Most replacement battery cables have very thin crimped terminals on the end with a larger hole designed to go over the typical 3/8" Chevy style terminal studs. There is very little wire left when that large hole is punched thru. Proper terminals with a 5/16" hole can be purchased from hardware stores, welding shops, or even "home box" stores. The good terminals can be crimped on and soldered properly. Some electrical or welding shops will crimp on terminals for a fee.

Most of the wire terminals and connections in these trucks are crimped at the factory. Factory crimping is a good process but failures can occur. The electrical systems in these trucks were designed to last about 5 years, maybe 10 at the outside. -Or maybe just thru the warranty period. Those crimped terminals have been exposed to thousands, perhaps millions, of temperature changes and heatings due to current flow and ambient temperature changes. Every time current flows or the metal heats up they expand and contract and the wire expands and contracts at a different rate than the connector body. This tends to loosen the connection which creates a higher resistance and more heat. The higher the temperature the more the metals expand and react with atmospheric and environmental contaminants which produces corrosion. Corrosion causes an increase in resistance which produces more heat in a vicious cycle. These electrical systems are OLD! Tiny amounts of corrosion can cause the engine gages to malfunction. The voltage drops in wiring connections cause the headlights, turn signals, and other lights to be dim.

The only "cure" for this aging process is to disassemble the connectors and wiring harnesses. Every crimp and connection has to be examined, cleaned, re-crimped, and soldered. Some may have to be replaced. Solder any replacements. When the wiring connectors are reassembled coat the contact surfaces with silicone dielectric grease, the same stuff that is used on spark plug boots. This helps to seal out environmental contaminants, moisture, and oxygen from the connections. They will still make metal to metal contact. Very dilute muriatic acid will clean electrical connections just rinse very well. Even toilet bowl cleaner etc will work if it has acid in it.

For high temperature connections like headlights and blower motor resistor connections use high temperature connectors available from appliance repair shops. They use them for wire connections to heating elements. The standard crimp connections found in stores will not last long with the heat exposure in these connections. You can solder those crimp terminals with silver solder also. Silicone dielectric will boil off of these connections but I sometimes use it anyway.

Crazy Dash Gages:
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I do believe that we must realize these instrument systems are 25-30 years old and were never designed to operate more than 10 years at the outside. The instruments operate on a very small amount of current and low average voltages so any amount of oxidation on any of the connections will cause them to read wrong. To make the Ford gages read properly for many years to come all you have to do is clean ALL of the connections and protect them from corrosion and oxidation with a little silicone dielectric grease. Once you have done this they will operate great!

The Instrument Panel Voltage Regulator (IPVR) is hard to check since it is just a thermal "flasher" unit just like a HD turn signal flasher. The output voltage goes to 12V and ground in a pulse fashion. Supposedly it averages out to 5V but it takes an O-scope to see the pulses and average the voltage. If the IPVR has a bad ground it will supply full battery voltage to the gages causing them to peg to the right at times, sometimes continuously. This is the most common failure mode. Clean the connection as described below and use a star washer under the IPVR retaining screw to help maintain pressure on the joint. Eventually the plastic will creep and the joint will lose contact again tho.

The flex circuit on the back of the instrument cluster can be cleaned with a variety of methods. Remove the flex circuit and very gently brush the contact surfaces with a fiberglass spot abrasive brush found with the touch up paint at the parts store or some people use a regular #2 pencil eraser. Very gentle cleaning is required, if you remove too much copper the circuit is ruined. Use a damp paper towel to clean up the dust afterward. Coat the contact surfaces with a thin layer of silicone dielectric grease and reassemble the panel.

Ordinary crimp connections can be cleaned with brake cleaner then dipped in a dilute (1 part in 10) solution of muriatic acid available from the hardware store. Rinse the connector thoroughly in running tap water. Blow out with compressed air or blot dry with a paper towel. Solder the connection. If the connection has been properly cleaned solder will wick into the joint. This will not work with a connection that is obviously overheated or corroded. Replace those connectors.

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Good,luck.

 

Man...I've got my work cut out for me. Thank you for the reply's. It is exactly what I was needing.

 

I would guess the blinker issue may be a bad turn signal switch in the steering column. As in the post by Crazed Fox, I would remove the instrument panel and try cleaning the contacts and printed circuit, also clean the 3 amp fuse in the fuse box. There also should be a black wire coming from the printed circuit connector on the back of the guage panel...make sure the ground is good there.

 

Well, I'm on my to going down this check list. I have removed the instrument cluster and replaced all bulbs also cleaned connections on the circuit as stated above. I went through the fuse panel and replaced all the rusty ones and checked continuity for good measure. I appear to not have dash lights still...will check to make sure when its good and dark. left and right blinker indicators are working now. However when the headlights are on, the left blinker indicator stays on (not blinking). These problems might fix themselves as I work through the rest of the wiring (not fun in freezing weather), but I will take thoughts on the matter.

Thanks again for all the good info.

 

Check the bulbs on the outside of the truck on the left side. Check the bulbs for crossed fillaments. Comon problem.

After that, if it doesn't fix your problem, check the lamp sockets, and wires between the marker lamp circut, brown wire, and the turn signal wires for a short between them.

 

All the inst. cluster lights/dash lights are run by the blue wire with red stripe. Power comes from Headlight switch and runs through 3amp fuse in fuse panel and loops through the cluster and to other dash lights, including the Park, Neutral, drive selector on steering column. Are any of these lights working, or is it just the instrument cluster?

 

Alright, went to check the cluster lights. Here's what I got. The cluster now has its back light, with the exception of the right side. That's probably a new bulb not making contact. The cluster lights are flashing. Very rhythmically, like a blinker. Same story with the lights on the blower / heater..all blinking same tempo. Also noted that I have no dimmer function on these lights. Rheostat on switch appears to still function because the dome light still comes on at the click.

 

Is,
__this with or without the truck running?

 

Interesting question, odd answer. when I first put the key in lights cam on steady. Fired up the truck and things started blinking. Turned the truck off and they continued to blink. Pulled the key and put it in again to reset. Lights were steady for a couple of seconds then started the blinking with the engine off.

 

Problem: Turn indicator that was turning on when the lights were turned on has been identified and fixed. bad ground at front left bulb. One Down. Blinking dash lights are still a mystery.

 

My gut feeling. Headlight switch. It is what distributes the current and I had the same problem on my 89 ranger and was the headlight switch. I would replace, I bet your problems will go away.

 

hmm, because of the pulse (blinking) I was wondering if it might be the instrument voltage stabilizer?

 

Check the voltage coming out of the headlight switch. Wires should be blue/red stripe, and see if you are getting the pulse there. If so maybe switch? I don't think the voltage stabilizer powers any of the circuit for the cluster lights...only the gauge functions. It's power comes from I think a purple wire that reads, resistor wire, do not cut.