I havent taken apart my early W124 temp display (it looks like it has the integrated board)

But I have to later 5 pin temp displays. With the integrated board can I somehow swap to a 5 pin?

I did some experimenting with the various displays a year or so ago. It did not go well -- I could not swap the little LCD readout panel among different electronic boards and get them to work. I think the pinout changes from version to version. I didn't put enough time into the process to really be sure and there is no available documentation unless you have a friend at VDO and even then the design is 20-30 years old so nothing may have survived. To be safe I would advise against swapping parts inside the black plastic case.

The complete display can be swapped with no problem as they all work the same. You can swap Fahrenheit for Celsius and even 4-pin for 5-pin if you rearrange the pins in the plugs.

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Guess I should have grabbed the plugs from the junkyard instead of the display. The displays I have came out of E320's and do not have any signs of black smudges. So they might work?

Ill go back and get the plug and then switch plugs. Even if I do not tap into the speed sensor block it should work, correct?

I have a '85 W201 190D. The odometer recently stopped so I'm going to be pulling the cluster to address that problem. While I'm in there I'd like to also change the current sporatic Celsius unit with a Fahrenheit one. The sporatic systems are the unit usually works when the car is first started (expecially when the temporature is cold) and will read accurately for a few minutes then goes blank.

Based on your info above, I wouldn't have a VDO produced unit? Is so, what donors should I pull a replacement unit from? Since my current display sporatically provides an accurate reading, is it likely my sensor is functioning and won't need to be addressed?

Thanks!

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You can't always get what you want, but if you try sometime you just might find you get what you need.

If my LCD was blacking out, I'd just be tempted to buy something like this off ebay for sub-$10, and separate the LED from the electronics and stuff it all in the spaces within the original temp gauge. If you look harder you can get ones that are "auto" dimmable (input from headlight switch kinda thing).

0 36"Blue LED Digital Car Thermometer Temperature Meter 55 125°C DS18B20 Sensor | eBay

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Cheers!
Scott McPhee

1987 300D

I had such a thing in my W123, which didn't come with an outside temperature gauge. Your eBay suggestion looks good and the price is certainly right. Do you know whether the temperature sender in that product is permanently attached to the display? That would make it more challenging to install in the instrument cluster if the sender couldn't be detached. Also, I notice that the item is in China.

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

The W201 got a physically different temperature display; the W124 (and W126, for that matter) versions won't interchange. I can't speak to the insides -- they may interchange but I've never taken a W201 unit apart. To be safe you'd have to get a replacement from another W201.

If your unit works occasionally it may just be a dirty contact in a plug or a wire that has most of the strands broken at a connector and is just about to pull loose. That is something easily fixable once you track down the problem. The pins in the connectors may be silver-plated and shouldn't be scrubbed hard with steel wool or sandpaper -- the plating will come off. Pretty much any metal polish will remove the corrosion -- I use Mother's Mag Wheel polish and a Q-tip for such things.

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Bringing up this older thread as I need assistance. My ambient temp display is the 4 wire version and was working fine. I pulled it out to replace the bulb with an LED (including resistor). After replacing, bulb lights up fine when I connect battery directly the gray (pos) and yellow (neg). When I put the unit back in the car, I am not getting any light or temp read out. I have a spare unit that I tried and getting the same result with both. Is there a way I can try to get a temp readout connecting it directly to a battery? I'm thinking the LCD is not getting power, however am not sure how it is suppose to as there does not appear to be any physical contact between the PC board and LCD...how does this get power? Any ideas to test or get working would be appreciated. Thanks.

The green wire is not negative ground. The wiring for the 4 wire version is: pin 1 +12 volt power - black/red, pin 2 ground - brown, pin 3 temperature sensor - green and pin 4 is illumination - gray/blue.

Thanks- my wire colors are grey (which I believe is illumination)-pin 2, yellow-pin 4, green-pin 3 and white-pin 1. When I put 12v to grey and ground to yellow, the bulb lights. I can't get the LCD display to come on regardless of which wires I apply power/ground. I'm starting to worry that when I soldered the LED and Resistor on the board, I messed up the board and killed it.

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The colours that I gave you are for the mating harness although the pin numbers and functions should be accurate.

Awesome. I'll take a look. Thanks.

The LCD contacts are along the edges. There are two small "rubber" strips that act like brushes. There is someone on one of the lists who rebuilds these, new lcd and everything, maybe on 190revolution?

The five and four lead versions should interchange. The 5th lead is a speed sense, which corrects for roadspeed airflow. If it's missing, the gauge works without correction.

So I should get voltmeter reading of 12v on pin 1 of the harness? Does ignition need to be on?

I do not have any rubber strips on either side of my LCD. The white lamp diffuser is the only thing between the PC board and the LCD/reflector.