Two Tiny Electrical Gremlins

[Minuit]

So I've recently replaced the badly melted fusebox in the '89, and all of the things that are supposed to work now work, but I have two more questions.

 

1. Is the dash clock supposed to be active all the time? The clock I have has a separate bulb. If I turn the headlights on the bulb will light up and it will show the time even with the key off. Is this normal?

 

2. The volt gauge is a lying sack of $#!&. The battery and alternator are in perfect working order, but the volt meter never comes even close to the 14 volt mark. With the key on engine off the volt gauge stays on the 9 volt mark. Would adding another instrument cluster ground solve this as some googling has led me to believe? I'm going to add a ground per Cruiser's tips anyway, but I'm just wondering if I should expect my volt gauge to read properly after doing that.

 

Danke.

[cruiser54]

Clock has 2 illuminations.

 

Only visible with key On.

 

Changes intensity when headlight switch is activated.

 

As for the volt gauge. add the ground and report back please. 

[HOrnbrod]

1. Is the dash clock supposed to be active all the time? The clock I have has a separate bulb. If I turn the headlights on the bulb will light up and it will show the time even with the key off. Is this normal?

Danke.

 

Check your 12V inputs at the clock connector as follows:

 

Pin B   Orange wire     "Panel intensity input" (+) - 12V variable controlled by headlight knob rotation

Pin F   Purple wire       "Ignition on input" (+) - 12V ignition switched

Pin G   Blue wire          "Dim display input" (+) - 12V applied when headlamps are turned on

Pin C   Pink wire          "Battery input" (+) - 12V constant memory

Pin A   Black wire        "Ground" (-)

[Minuit]

Clock has 2 illuminations.

 

Only visible with key On.

 

Changes intensity when headlight switch is activated.

 

As for the volt gauge. add the ground and report back please. 

 

I added the ground, and it doesn't seem to have changed the reading any. Here's key on, engine off:

 

Key on, engine running:

 

And then a little bit later.

 

 

It fluctuates between where it is in the pics and almost to the 14 volt mark. With it running I saw about 14 volts at the battery as I should.

 

 

1. Is the dash clock supposed to be active all the time? The clock I have has a separate bulb. If I turn the headlights on the bulb will light up and it will show the time even with the key off. Is this normal?

Danke.

 

Check your 12V inputs at the clock connector as follows:

 

Pin B   Orange wire     "Panel intensity input" (+) - 12V variable controlled by headlight knob rotation

Pin F   Purple wire       "Ignition on input" (+) - 12V ignition switched

Pin G   Blue wire          "Dim display input" (+) - 12V applied when headlamps are turned on

Pin C   Pink wire          "Battery input" (+) - 12V constant memory

Pin A   Black wire        "Ground" (-)

 

 

I'm leaving Columbia today and I won't get a chance to mess with the truck until next Thursday, but when I get back I'll definitely check the plug. 

 

Here's what it does with the key off. I can barely see "4:27" on the clock.

 

Do you think it'll run the battery down if left like that? No idea how much current the LCD in the clock draws.

[cruiser54]

 

1. Is the dash clock supposed to be active all the time? The clock I have has a separate bulb. If I turn the headlights on the bulb will light up and it will show the time even with the key off. Is this normal?

Danke.

 

Check your 12V inputs at the clock connector as follows:

 

Pin B   Orange wire     "Panel intensity input" (+) - 12V variable controlled by headlight knob rotation

Pin F   Purple wire       "Ignition on input" (+) - 12V ignition switched

Pin G   Blue wire          "Dim display input" (+) - 12V applied when headlamps are turned on

Pin C   Pink wire          "Battery input" (+) - 12V constant memory

Pin A   Black wire        "Ground" (-)

 

Is that info from the 89 manual?

[AMC86Kid]

your alternator should be putting out 13 to 14 volts to your battery depending on how much electronics are running in your vehicle 

now your voltage gauge in your dash just samples the reading it gets and displays it so if its off there are a few reasons why

 

1 its not grounded but you said you grounded it i would just make sure its grounded properly

2 there could be a faulty gauge or connection where it reads (the electronics after time tend to lose there linearity and fall off of its reading)

3 poor continuity (check all the wires it connects two a corroded wire or connection can drop 2-3 volts easily especially from all the shaking you get from driving)  

[cruiser54]

If you want to get carried away:

 

http://www.jeepforum.com/forum/f11/renix-voltage-gauge-fix-684375/

[Rockfrog]

Your volt meter reads whatever voltage remains AFTER the blower, wipers and (to some degree) headlight draw. There are others pulling it down but th big one is the blower. Shut it right off and the reading will go up. If not, the blower speed connector is most likely melted somewhat and you are seeing the results of resistance.

Mine does the exact same thing. Has had extra ground for a few years now. It's not a ground issue, it's an overloaded brown wire issue. The Guage just shows what there after all the draw down due to the way it is wired.

We talked a few months back about adding a relay off the brown wire to the blower and another to the Wiper circuit, which are the two main loads on that brown wire. Which in theory should allow a closer reading at the guage due to less overall load sucking voltage.

 

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[Minuit]

Thanks guys. I'm really not worried about the volt gauge. I'm sure at some point it'll bother me enough to fix it properly but there's 27 years of deferred maintenance to catch up on before I worry about the silly gauge. I just wanted to see what the Renix peeps had to say, because all of these Renix-isms are totally foreign to me.

[Eagle]

There is nothing "Renix" about a volt meter. The Renix system controls ignition and injection. Everything else is just wiring.

[HOrnbrod]

Had a similar problem with the VM dropping lower than I wanted it to whenever I used the headlamps and dual electric fans together. I broke out the wiring diagram and traced the voltmeter + terminal sensing lead back to the PDC fuse block at the fan feed wire. Removed it, and rerouted it to the big positive mains cable that feeds the PDC. Now the VM barely fluctuates off mid-scale. Of course it's wired differently on a Renix, but you can probably do the same thing. I prefer the VM to read the overall charging state of the battery, not drop or flicker whenever it sees a load.

[Minuit]

There is nothing "Renix" about a volt meter. The Renix system controls ignition and injection. Everything else is just wiring.

I think that's a silly and pedantic point to make, and I never described the volt meter specifically as Renix. To me a "Renix-ism" as an odd characteristic of a Renix era truck.

 

Had a similar problem with the VM dropping lower than I wanted it to whenever I used the headlamps and dual electric fans together. I broke out the wiring diagram and traced the voltmeter + terminal sensing lead back to the PDC fuse block at the fan feed wire. Removed it, and rerouted it to the big positive mains cable that feeds the PDC. Now the VM barely fluctuates off mid-scale. Of course it's wired differently on a Renix, but you can probably do the same thing. I prefer the VM to read the overall charging state of the battery, not drop or flicker whenever it sees a load.

I'll have to poke through the FSM to see how the 89 wiring does it and do something similar when I decide to fix it. I'd much rather do that than run a new power wire to the gauges from the battery. If I come up with something I'll report back.

[cruiser54]

 

There is nothing "Renix" about a volt meter. The Renix system controls ignition and injection. Everything else is just wiring.

I think that's a silly and pedantic point to make, and I never described the volt meter specifically as Renix. To me a "Renix-ism" as an odd characteristic of a Renix era truck.

 

Had a similar problem with the VM dropping lower than I wanted it to whenever I used the headlamps and dual electric fans together. I broke out the wiring diagram and traced the voltmeter + terminal sensing lead back to the PDC fuse block at the fan feed wire. Removed it, and rerouted it to the big positive mains cable that feeds the PDC. Now the VM barely fluctuates off mid-scale. Of course it's wired differently on a Renix, but you can probably do the same thing. I prefer the VM to read the overall charging state of the battery, not drop or flicker whenever it sees a load.

I'll have to poke through the FSM to see how the 89 wiring does it and do something similar when I decide to fix it. I'd much rather do that than run a new power wire to the gauges from the battery. If I come up with something I'll report back.

 

Did you view this link?

http://www.jeepforum...uge-fix-684375/

[Minuit]

Yes. I wonder if there's a way to move the sensing point like Don said rather than running entirely new wiring. If not I'll follow the procedure in the link.

 

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[HOrnbrod]

I took a peek at the 88 Electrical manual. The positive WHT/BLK sensing wire to the instrument cluster VM + terminal comes from the hot side of the 7.5A "Gauges" fuse in the Renix fuse panel. You could pull that wire off there and extend it to the nearest B+ full battery voltage point.

[cruiser54]

I took a peek at the 88 Electrical manual. The positive WHT/BLK sensing wire to the instrument cluster VM + terminal comes from the hot side of the 7.5A "Gauges" fuse in the Renix fuse panel. You could pull that wire off there and extend it to the nearest B+ full battery voltage point.

Wouldn't the gauge read even with the ignition off then?

[HOrnbrod]

Good point - yes it would. To clarify, I don't have a schematic of the 88 fuse panel, but I'm sure there would be a good clean unloaded ignition switched point you could pick up on the panel.

[Minuit]

Now that's what I was looking for. I would have figured this out by myself rather than have y'all spoonfeed it to me but my FSMs are 130 miles away right now. Thanks much guys. :thumbsup:

[cruiser54]

Good point - yes it would. To clarify, I don't have a schematic of the 88 fuse panel, but I'm sure there would be a good clean unloaded ignition switched point you could pick up on the panel.

Did you read the link?

 

I like your idea better.....

[87MJTIM]

 

I took a peek at the 88 Electrical manual. The positive WHT/BLK sensing wire to the instrument cluster VM + terminal comes from the hot side of the 7.5A "Gauges" fuse in the Renix fuse panel. You could pull that wire off there and extend it to the nearest B+ full battery voltage point.

Wouldn't the gauge read even with the ignition off then?

 

 

No.  The fuse panel is powered from the Ign switch only in the Run and Start positions.

[cruiser54]

 

 

I took a peek at the 88 Electrical manual. The positive WHT/BLK sensing wire to the instrument cluster VM + terminal comes from the hot side of the 7.5A "Gauges" fuse in the Renix fuse panel. You could pull that wire off there and extend it to the nearest B+ full battery voltage point.

Wouldn't the gauge read even with the ignition off then?

 

 

No.  The fuse panel is powered from the Ign switch only in the Run and Start positions.

 

So, what's the plan?

Why did the guy in the link go to the trouble of using a relay? 

[HOrnbrod]

There are plenty of hot fuses in the fuse panel; they are not all ignition switched. Get your multimeter and check each fuse with the keys in the glove compartment.

[SVPete]

Your clock in the key off position looks normal to me. I can kind of make out mine without the bulb illuminating it also.

[87MJTIM]

 

 

 

I took a peek at the 88 Electrical manual. The positive WHT/BLK sensing wire to the instrument cluster VM + terminal comes from the hot side of the 7.5A "Gauges" fuse in the Renix fuse panel. You could pull that wire off there and extend it to the nearest B+ full battery voltage point.

Wouldn't the gauge read even with the ignition off then?

 

 

No.  The fuse panel is powered from the Ign switch only in the Run and Start positions.

 

So, what's the plan?

Why did the guy in the link go to the trouble of using a relay? 

 

:dunno: I was looking at the 88 Elect manual and trying to follow the guys instructions/directions.  I was lost.

 

From the 88 manual, the wire feeding the Ign switch also feeds power to: pwr windows, starter circuit, blower motor, and wipers

 

I would cut the Yel wire from the Ign switch.  This wire powers the gauge fuse and the TCU fuse.  This wire would charge the relay (86) when the ign is turn to Run or Start.

 

I would run wire from the batt to the power relay (30).  The second half of the Yel wire would feed power to the gauge fuse (87).

 

This way, you would isolate the gauge cluster from all the other components, but still power it with the key on Run/Start.

 

(I am not an electrical engineer, but on paper it looks like it would work.  Of course, Communism looked good...on paper.)

[HOrnbrod]

Why do you have to isolate the whole cluster? All you need to isolate is the voltmeter + sensing lead. For the HOs, it's easy; just locate and cut the sensing lead at it's PDC fuse and extend it over to the main PDC feed MAXI fuse, which is ignition switched. That way the VM sees pure charging voltage from the alt before it gets loaded down by all the branch circuits. 

 

Maybe it's tougher with the Renix system since they have no PDC, but by using the method it should be doable.