Broken Speedometer Repair (1 Viewer)

[gummycarbs]

When I bought my '94, the speedometer didn't work. I did some Googling and turned up the VSS as a likely culprit. There was a good deal on NOS Toyota units on eBay, so I bought one. Didn't fix it.

I read somewhere (here or maybe Expedition Portal?) about the speedometer circuit board looking 'burnt'. Sure enough, mine did, right at the top:



I took a brass brush to it (the 'toothbrush' type) and the "burnt" stuff came right off, revealing two damaged circuits:



The left half of the top circuit was still intact, but looked really sketchy, so I did a two-step repair on that part. The speedometer works great now, though the tripmeter is still non-functional, except for the tenths digit.



I don't know what caused the circuit to fail like that. I can't imagine that it's somehow collecting moisture there. The lower circuit is really thin, so I can see how it might eventually burn out, but it still seems weird. I noticed that there are a few capacitors that look like the Nichicon ESR capacitors that are known to leak and corrode circuits. Lexus guys have found that leaking capacitors are damaging their ECUs in a similar way, but I haven't read much about that on Mud. Here's a link to the discussion on Club Lexus:

All my crazy Lexus issues SOLVED!! (ECU-leaking capacitor) - Club Lexus Forums

Hope that helps someone.

 

[shocktower]

Yeah I want to fix my trip-meter, dam thing died

 

[22re92]

My circuitboard looks almost identical to yours, did this work?

 

[gummycarbs]

My circuitboard looks almost identical to yours, did this work?

Yep, it's been working great for months.

I recently discovered a product that would probably work great for repairing these kinds of problems without soldering: CAIG CircuitWriter. It's a conductive ink pen. $20 at Fry's.

 

[22re92]

Yep, it's been working great for months.

I recently discovered a product that would probably work great for repairing these kinds of problems without soldering: CAIG CircuitWriter. It's a conductive ink pen. $20 at Fry's.

Hah! I actually just tried that without success. Going to try doing the wire method you used.

 

[gummycarbs]

Hah! I actually just tried that without success. Going to try doing the wire method you used.

Ah, bummer to hear that.

 

[22re92]

Is there a particular type of wire you used to solder the joints together? Here's what mine looks like:

 

[22re92]

By the way, thanks for your fast response!

Update, attempted the wire solder without success. It's possible I need to make more connections or that my soldering skills are bad. Will attempt more tomorrow:

 

[gummycarbs]

When I did mine, I put a multimeter on contacts along the various circuits checking for continuity.

And you might want to get a softer brass-bristle brush. It looks like yours was a bit harsh.

 

[ScratchedFJ]

I have been working through a nonoperational speedometer and odometer (cruise control works) and I'm thinking I might have a burnt path like the images above. Is this circuit board located inside the cluster?

 

[ZMaster]

The odometer module sits inside the cluster. There is a thread somewhere about how to remove the speedo to repair the broken gears.