Hi,
So the oddities started happening about 2 weeks ago when I was on the highway and it was 111 degrees. The truck just shut off at ~65mph and I had to wait for it to cool down a bit and then after 30 mins it was willing to start and stay running. It happened again on the same trip, same fix. It was not an engine overheat though, the temp gauge read normal.

Then recently the 10A fuse that runs power to the fuel and temp gauge, outside air temp gauge, and gear selector indicator blew. I replaced it and within 30 mins of driving it blew again.

I have searched this forum and online quite a bit and people with similar, though different symptoms, have suggested it could be the ignition switch. Do you think that would have also caused the hot weather shutdown? For the engine shutdown I would have thought it could be distributor cap and rotor but I don't see how that would affect the gauges.

Any help is much appreciated. Thanks!

 

Hello Mark D,

Not sure what year you are driving. Not sure if that Outside Temp Sensor could cause
at 10 amp fuse to blow. I copied this from my AllData info.


The temperature sensor is mounted to the hood latch support bracket and is located near the center of the grille opening. An electrical connector attaches the sensor to the front headlamp harness. The sensor itself is a thermistor which provides a resistance that varies with temperature. If the thermistor is suspected of being defective, an ohm-meter can be used to measure the resistance of the sensor. The sensor should be disconnected from the harness to conduct the measurement. The resistance values of the sensor should be as shown in the table.

The electronic module has the capability to detect a short circuit or an open circuit in the temperature sensor circuitry. The display will show "SC" in the temperature area if a short circuit is detected and will show "OC" if an open circuit is detected. If either display exists, the short or open condition must be located in the wire harness between the sensor and the electronic module.

Its a start for you.

Mark K

 

Wow, thanks for the info Mark! I have never seen SC or OC in the display but now I know how it is connected and where that gauge is should I have to get to it. It just shows "--" any place that a number would be.

I will have to get a multimeter and start poking around under the hood and in the dash. Sounds tedious, yes?

 

So I went ahead and replaced the ignition switch because all of my symptoms could be described by an ignition switch failure. $73 later the problem still happens. I would like to offer some more information in the hopes that anyone has a suggestion for me. I've tried to understand the electrical diagrams in the Haines manual but they don't include the 4wd circuit (that's the fuse that blows) and get too complicated for me anyhow.

So, backtracking a few months, I had an issue where it would sound like the 4wd was partially engaging, I'd hear a buzzing noise while on the highway and as I pull off it gets slower and slower and by turning the wheel or with luck it would go away.
Then the electrical problem happened as stated - it was really hot out and without an engine overtemp, the engine died. It would crank immediately after but took a while to get it to where it would continue running.
Now, what I see is that my 4wd fuse (10A) blows out and when it does, the gauges (Fuse #4) go out with it, but don't blow their own fuse.

This tells me (and please let me know if I'm wrong) that the Gauges circuit is probably shorting into the 4wd circuit. Anybody have a clue where this could happen? I am scared to get behind the plastic wall behind the dash facade where the harnesses lie but would give it a go if need be.

 

Just for kicks I thought I'd see if the the 4wd selector switch had gone bad, since it is near the gauge cluster. I unplugged both cables that come out of the switch and then put a new fuse in the breaker and it still shorted.

As a starting point, does anybody have a circuit diagram for the 4wd circuit?

[Edit: Found a diagram, but it doesn't offer me much help by itself ]