@mrfox Well I assumed that the dial is translucent hence the recommendation but at the end of the day the choice is yours… 😉
@radtekman ohh 100% , I face a lot of these issues too with this stuff xd , I have never designed a circuit before but know how my point to point wiring circuits on my VW Bus (vw bay window) works. It’s as simple as one can get with a system.
@ovi4 Would there be a way to do all of this but use my existing rheostat? I don’t like the idea of drilling holes in my 50 year old dash to add a pot for dimming LEDs.
I finally made an imgur account just so I could upload images here . So these are what my clusters would look like bulb wise and gauge.
Note: These pictures are not mine and all copyrights go to their respected owners. Thanks
@mrfox Well, is not as simple as it looks. since three are some factors to consider but surely can be done:
Options:
Assuming that your vehicle is about 1973-1975 TYPE 2 (window bus) production (since you’ve said that is 50 years old!) and according to what electrical diagram I have found/fetched from the internet it looks to me that only 2 or 3 of the incandescent lamps (according to you there are 8 incandescent lamps) are included in the dimmer circuit . Again, I assume that I’m looking at the right kind of electrical diagram here and comparing it with your provided IMGUR picture it seems to match :
So the way I see it is that you’ll need to put a resistor of either 430 or 470 Ohms in series with each of the 3 LEDs (individual resistor to each LED) and keep the existing rheostat with no modifications needed and at least “on paper” it should work . It is the easiest, most efficient way I see so far. Try the 430 ohms value first and if it;s too bright then swap to the 470 value.
As for the other (remaining) 5 Lamps, you may try to do the same (1 resistor/LED with the same value as above).
But Like I said, they seem to simply do other jobs and they are not part of the dimming circuit (again, according to the diagram). You might have your own technical book that shows some electrical diagrams and can compare them with my diagram to see if it matches. Is always a good idea to make sure you’re on the right track… 😉
Keep in mind that the above solution is only valid providing that the battery voltage is indeed 12V and the diagram I’m looking at is the correct one and what you’ve said in regards to the LED specs (forward voltage 3V and current is 20mA) holds true.
Very easy to try in virtually no time at all and if it doesn’t work is also very easy to revert to the original and…hey…there is always a plan B or a C….. 😉 😉 😉
@mrfox PS: It is always a good idea to either measure (with an ohmmeter) or look at the body of the rheostat in order to discover the maximum resistance value of it. Or it might be stated somewhere in a technical manual.
And it must be done well before attempting any LED mods. The reason is that it’s helpful to work out what other adjustments can be done in case the dimming function no longer works as expected or not at all after you’ve fitted those LEDs.
By the way there seem to be some sellers that will sell you a bunch of 8 LEDS as a direct replacement (and they should have the resistors already included inside each LED lamp) for your VW Window Bay T2 and one of them is here:
Reading the listing description it claims that the color temperature is 3000K and you can even pick certain colors that you might prefer instead of just the typical “Plain Jane White”. … 🤠 and the price seems ok-ish.
@ovi4 Thanks for replying , i was going to get these except that they have SMD’s with no cooling so they often burn out in a month or less.
I have been looking on and off for a month and still not sure if i want to get smd leds and hope they don’t burn out from being over current and then have to take the dash back apart which is a main as you have 4 clips to take off without loosing them and even more of a pain to reinstall without loosing while holding them under dash.
Kind of why i wanted to take the approach of just making my own with the diffused sealed LED’s, Reason why im wanting to try these diffused hobby leds are simply because they seem to last for years if driven at their correct resistance values. I do think i can get those housings empty where i can stuff my own parts into including led’s.
—–Rheo Stat Dimmer Switch + Headlight—–
You can see on pin 58B this is the positive wire that goes to the Gauge Bulbs on the cluster which is dim-able via rheostat.
The incandescent bulbs i want to replace with led’s are 1.2watts a piece. NOTE: Not all clusters has lighted Heater/Cool Air controls and many didn’t have an automatic transmission which are quite rare.
I might still try out those SMD led’s for the Gear Shifter as that’s a little bit easier to open up , but am afraid to use them seeing how many of them burn out as reported by many people who bought and used them. I’m seeing incorrect resistor values that are used when assembly from factory or who ever makes them to get that overly bright light not to mention many of them aren’t dim-able or don’t dim very well. (turned all the way down but still too bright) or (turned all the way up and too bright)
So many people have reported going back to incandescent bulbs after a month or more.
@mrfox Well…if that’s the case you’re certainly better off making your own LEDs and give it a try to see if the rheostat still does work as to have pleasing results if not there’s always a plan B…Good luck and if you get to a happy solution feel free to showcase your results here. I’m kind of…curious myself to find out… 😉 … 👍
Even with a rheostat, I would look to at a current limiting resistor to give a longer life.
Larry – N7LUF
I am late to reply, but you can absolutely under drive the LEDs. They are more than bright enough these days. Of course, the hardest thing for LEDs is heat. Get a high power LED and run it low, still plenty bright but extends the life a lot. Even LEDs for my house, I get say 75 watt bulbs and take one of the paralleled current set resistors out (half power) and you get way better life out of it. If you need it brighter, just put the resistor back in (or adjust value). I always try to overrate everything for that reason.
Radios + Tubes + Scopes + Cars= Nothing better!
Doing some planning still. May just use incandescent bulbs for the time being if i don’t have a solution. I am not very technical with building circuit boards and my understanding of parts are small. ( I should of stated this befor. )
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