98 TJ electrical issue - Gauge cluster dead

[hillstrubl]

1998 TJ that recently had a very dead battery. It would start and run (albeit a bit rich) just fine with a jump. When it was revved a bit or after a while of charging the gauge cluster would come back to life. After the latest jump it hasn't woken up. The battery itself has been replaced with a brand new one, charging/holding the charge fine (alternator is fine), but the gauges are dead. What's interesting is that from what I can gather its on the same circuit as the under hood and dome light (which are both also dead). I haven't found any obviously blown fuses, but I'm still checking that. When the gauge cluster was pulled it was found that the pin for both constant and ignition switched power are both dead.

So the gauges themselves might be fine? We're going to run a jumper to those pins to temporarily see if the gauges wake up.

Anything else we can look at?
What "feeds" the gauges? The ECM? If so wouldn't it have issues starting running?

 

[wADVr]

Check the grounds. Especially the PCM ground. I will also mention checking the fuses for voltage drop across them. I once had a fuse (10Amp) to the PCM that was partially burnt which checked good on continuity test but would only allow 9-10 volts through which caused all sorts of issues. My money would be on a loose ground though. See if you can find the wiring diagrams for that model. This should identify all chassis grounds for troubleshooting.

 

[hillstrubl]

That makes sense, maybe when I was revving it before it was at a high enough voltage that it "found" an alternate ground.
I'll report back.

 

[hillstrubl]

Some updates, the whole dash is apart. No codes at all from the OBDII reader. Gauge cluster doesn't respond to self test at all.

• Power at fuse 10 (Labeled instrument cluster) inside block with ignition on
• No power at fuse 17, inside block, key on or off
• Gauge cluster's C2 blue plug pin 8 switched power is dead, pin 9 constant dead
• Under hood light and courtesy lights have power (apparently they are on the fuse 17 circuit)

Tried to manually give power (and ground) to C2 plug pins to see if the gauges did anything, but not sure that's actually a test of anything.

Questions:

• Why is there no power to the gauge cluster (needles, etc) when fuse 10 seems fine and is fuse 17 involved at all?
• IF fuse 17 was the source of C2 pin 8 (switched) or C2 pin 9 (constant) and its dead at the fuse box, then why are both pins dead at the C2 plug?

My hypothesis is that the gauge cluster itself is fine and the problem is earlier in the circuit. Why I don't understand is why does fuse 17 seem dead, but things powered by it are fine?

 

[Zeep]

Assuming you have the 4.0. Check integrity of the harness behind valve cover on fire wall.
Also physically remove and clean every ground you can find. Known issue on older TJ's.

 

[hillstrubl]

Yes, 4.0. can you confirm if/what fuse 17 has to do with powering the gauge needles?

Was going to work on the grounds too, tried to take the main one off of the firewall (just under the hood light) but even an impact couldn't move it, soaked in pb blaster for another day.
Will check on that harness too. Thanks

 

[GlennA]

Did you look at fuse 12 in the interior?

 

[hillstrubl]

Did you look at fuse 12 in the interior?

Check for constant or switched power?

 

[GlennA]

Based on what it controls, I would think switched. I'm only looking at the fuse panel labels, not a schematic.

 

[hillstrubl]

will check, thanks

 

[GlennA]

From what I've been able to find, fuse 17 under the hood isn't associated with the instrument cluster on a 1998. Looks like it is rear defrost on a factory hardtop.

 

[BulldoginaJeepwithaColt]

Goto the WranglerTJForum - search there, if no luck DM a guy named Jerry Bransford.

He is the TJ guru!

Good luck!

Sent from my SM-G981V using Tapatalk

 

[hillstrubl]

Goto the WranglerTJForum - search there, if no luck DM a guy named Jerry Bransford.

He is the TJ guru!

Good luck!

Sent from my SM-G981V using Tapatalk

Thank you for the tip. I'll do that.

 

[BulldoginaJeepwithaColt]

I have 98 TJ too. I am sure you already did this but clean and double check all your grounds. Also check the connections at the PCM.

When you find out what it was please post here, I have had my issues chasing electrical gremlins with mine in the past 3 years.

Oh yeah, save yourself some grief only buy MOPAR sensors, except for the Oxygen sensors. You can buy the cheaper NGK sensors (they are what MOPAR used.)

Sent from my SM-G981V using Tapatalk

 

[Zeep]

Goto the WranglerTJForum - search there, if no luck DM a guy named Jerry Bransford.

He is the TJ guru!

Good luck!

Sent from my SM-G981V using Tapatalk

Jtec is your guy over there!