How to read znr or mov?

[Mad_Professor]

I got a nissan instrument cluster with obvious blown znr
I'm not familiar with them since I never replace them. This is a first for me.

How does one read details on the znr/mov for replacement?

[delaware74b]

Re: How to read znr or mov?

I'm not sure on how to ID the zener diode, but you may want to check D1, D2, D3. All 3 look like they're damaged (split, burn/splatter on the board).

What's the history on this cluster? I'd suspect damage with power on the comm/data lines from the ECU or another component shorted on this board.

[Mad_Professor]

Re: How to read znr or mov?

Well ZD is zener on the board, ZNR1 is the MOV? I think, that's what is blown.
TR1 is the transistor d2139.

2000 sentra, all stock, no mods.

Long story short, he did errands all day, last stop at the grocery store, got in and started, battery light and airbag light came on, car drove home fine, he messed with it, disconnected the battery while engine was running to see if alternator was working, engine kept running.
He didn't think it was the alternator. He check fuses found "battery electronic" fuse in dash box blown, replaced it, blows immediately. Calls me for advice, told him usual suspect is alternator, check the charge voltage, then mentions fuse then told him he got a short somewhere. A week goes by, he calls again, ask me to come out and take a look and tells me alternator was putting out 17V on his DMM and he replaced it and voltage is now battery voltage of 12.6V, doesn't seem to be charging. It still blowing that one fuse. I look up the fuse number and wiring schmatic, see it's key switch, security ind. light, comb. meter, TCM, data link.
Check the fuse terminals, found 12v on one, no voltage on other, disconnect battery ohm out terminals, 12v supply, open, other terminal .4 ohms to ground. obvious short. Disconnect ignition switch, no change. Pulled cluster, short goes open.

Pulled apart cluster what you see above is how I found it.

I will check the diodes and report back.

EDIT:
Going to have to remove ZNR1, can't do it tonight, I have to go to work.
D1-3 and D112 shows shorted in both directions.
D116 and D117 shows anode as open, cathode .532 ohms. The printing on diode seem to be similar to D1-3 and 112

[budm]

Re: How to read znr or mov?

Is the Diameter of that MOV 10mm?
If it is then it will be 10D220K = Max continuous 14V AC RMS/18V DC 10mm Dia.
https://www.mouser.com/ProductDetail...ugxn83Og%3D%3D

[delaware74b]

Re: How to read znr or mov?

D1-3 probably failed due to the battery being disconnected while the engine was running, causing the over-voltage condition.

The fuse blowing for TCM, combination meter (that's the instrument cluster) etc is probably from the shorted diodes and MOV.

[Mad_Professor]

Re: How to read znr or mov?

Sorry for the absence, got a lot going on with work.

Is the Diameter of that MOV 10mm?
If it is then it will be 10D220K = Max continuous 14V AC RMS/18V DC 10mm Dia.
https://www.mouser.com/ProductDetail...ugxn83Og%3D%3D

Measures 11.35mm across, how were you able to extrapolate that from the values on the blown one?

D1-3 probably failed due to the battery being disconnected while the engine was running, causing the over-voltage condition.

The fuse blowing for TCM, combination meter (that's the instrument cluster) etc is probably from the shorted diodes and MOV.

It's possible, We got another cluster to test with but no dash lights or working meters on that cluster, old one had working meters at least and partial dash lights. It's weird because the car date of mfg is 06/00 (month/year) and the cluster used incandescent lamps for the warning icons and the meters are screwed to the pcb. It's different on the test cluster, the warning icons use LEDs and used solid pins solder to the board that are pressed into the back of the meters and held the pcb with plastic clips, no screws, this was from 08/00 car. I went ahead returned that cluster and got another one from 03/00 car, this one used incandescent and screws as well and is identical to the old one, but haven't had a chance to run over to his place to test it.

If I get time this week I will remove the blown MOV and test the diodes again.

[budm]

Re: How to read znr or mov?

Most MOV manufacturers use the xxx (K) format for the Voltage rating. The S10 (or xxD, or Dxx) is typical format for the Diameter of the device). Since it is being used in the car, the spec makes sense.
Another example: https://cdn.badcaps-static.com/pdfs/...23c6387882.pdf