|
|
|
I can no longer see my instruments at night and want to replace the dim, 50-year-old original 3W bulbs with T10 5W LEDs. I've just ordered LEDs with the same dimensions (diameter 9.9mm, length 24mm, base width 9.3mm)so they'll fit into the instrument holes, and I ordered a dimmer on eBay in case these are too bright. I long-ago by-passed the original rheostat, which was getting cranky. It wouldn't work with the LEDs anyway, as they are not subject to voltage control.
From the looks of things, power comes through the rheostat, now bypassed, and the bulbs are wired in two legs, branching from one of the speedometer bulbs. The heater control light is included in this chain, with all lights being individually grounded to the metal of the dash. Does this individual grounding make this a parallel circuit?
I'd appreciate any advice I can get from anyone who has already upgraded their panel lights, including they types and P/Ns of the bulbs they have used. If my experiment succeeds (not sure yet how to reach the bulbs for the two temp gauges), I'll report back with details.
|
|
-
|
|
|
Many thanks for the great advice. I just ordered a set of 10 10mm OD T10 sockets with pigtails. This puts my total investment with LEDs, dimmer and sockets up to about $20. Going to take this by the numbers. Will try the LEDs in the speedo first, since they're pretty easy to get at. If I like what I see, I'll just go on and replace everything and be done. If they are too bright, I'll try the in-line dimmer with the existing circuit. If that doesn't work, I'll build a new wiring run using the pigtail sockets all rounded back through the dimmer and test it out of the car. I'll give a complete report along with all the part numbers and nay needed photos when I'm done.
|
|
-
|
|
|
Progress report. Seems I was one measurement shy of a load when I researched my LEDs. (Amazon, SIGANDG 10 Pieces 194 LED Bulb White DC12V 6500k 120LM COB LED Replacement Bulbs,168 LED bulb,2825 194 T10 W5W LED - $6) I checked the base width, but not the base thickness. Turns out the "plastic" LEDs' base thickness is greater than that of the glass incandescents. So, in order to fit them into the existing holders, you have to widen the contact considerably with a flatblade screwdriver. And, as suggested, make sure you have the polarity correct as the ground is accomplished through the holder's contact with the instrument.
Meantime, I tested the $2.79 dimmer (https://www.ebay.com/itm/123822658760) on a single LED, using one of the $7.99 for 10, 10mm dia. sockets with pigtails (https://www.ebay.com/itm/123822658760), and it worked perfectly. The seller agreed, however, that the grounds will have to come through the same side of the dimmer that the power exits.
So now I have the four undimmed bulbs replaced in the speedo and tach and, in the garage, at night, it is incredible. Nice, slightly greenish glow and Wow! I can actually see everything clearly.
I'm stopping at this point because I want to drive the car at night to insure that these lights aren't too bright and cause my aged-night-vision eyes problems. That will have to wait until the current snow and attendant salt are washed away by a good rain. If so, i'm going to have to build a completely new wiring harness, incorporating the dimmer, using the sockets.
Meantime, can anyone tell me how the hell to get at the bulbs in those two temp gauges between the tach and speedo? Seems almost impossible.
|
|
-
|
|
|
Yes, wedge bulbs need to be more carefully sized than you might think, as attested to by my own small collection of spares that don't fit into sockets.
If you've now got plenty of brightness, just for jokes try hooking up that old dimmer again. Even though it's a varistor and not chopping the volts into pulses, it should give you some LED dimming before the LEDs blink out. You may find that useful when you're on the highway at night and your night vision is slightly spoiled by having too bright a dash in your peripheral vision.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now
|
|
-
|
|
|
Great advice. Actually took a crack at those temp gauge bulbs, and through likely one of history's greatest examples of manual dexterity, got those two bulbs replaced.
This job really demands removing the seat and the steering wheel to get "comfortable" access, and since I was so pleased with the tach and speedo illumination, I thought I'd go ahead and do everything in order to avoid having to go through that removal process again.
I'll report back if/when I need to try the original dimmer again.
|
|
-
|
|
|
Do you have a car cover? If not just throw a thick blanket over the car so you can do your "night time" testing.
|
|
-
|
|
|
Actually have tested them in my darkened garage and they seem great. But that's not the same a being on the road with the glare of oncoming headlights. Raining today and tomorrow. Hope to do my night time test following that. Stay tuned.
|
|
-
-
|
|
|
Hi Dave. I did this exact conversion in my 1800ES several years ago so the details are foggy. Here's what I recall.....
I used this dimmer:
https://www.oznium.com/switches/led-dimmer-knob
It fit in the same location as the original and I was able to retain the original knob.
The bulbs were some sort T10 wedge base 5W that I don't see on that supplier's web sight any longer.
As Dave S mentioned, I found the bulbs to be polarity sensitive so I had to bench test them first and mark the + and - sides with red and black Sharpies. You may find some bulbs nowadays that aren't polarity sensitive.
Another, more unpleasant, surprise I ran up against was that I couldn't use the same bulb grounding method as the incandescents. The way I was told the LED dimmer works is that it sends a constant 480 hz signal to the bulbs. The dimmer varies the 480 hz wave shape which makes the LED dimmer or brighter. So I had to run a separate negative ground path from the bulbs back to the dimmer switch. I had a spare original instrument lighting "daisy chain" harness (red wires) so I rewickered it to add a negative wire running alongside the red wire back to the dimmer. Since the original harness is wrapped up with a much larger "main" harness I chose to just leave it disconnected and stowed up out of the way.
Hope this helps.
|
|
-
|
|
|
The bulbs themselves are wired in parallel in your dash, each with their own path to ground. The original rheostat dimmer would be in series ahead of all the bulbs down the two branch lines. If the T5 LEDs are rated for 12V use then the bulbs should be mounted as before. The low voltage LED elements will internally be in series and depending on the number of LED elements may or may not be internally resistored. When mounting the bulbs you will need to pay attention to the bulb +/- orientation in the socket. Depending on the design of the bulb you may find there are noticeable viewing angle differences in brightness and perhaps being too pinpoint for use in dash illumination.
If the bulbs say dimmable then you can put a new dimmer rehostat in series as before, but the rheostat range used with LEDs is often different than for incandescents. Most important for brightness is a zero Ohm rheostat range. The original dimmers often weren't zero ranged and why many people bypassed them (as I did with my '74 140). It may take a bit of trial and error to find an appropriate rheostat to work properly with the combined wattage load. If the bulbs are not listed as dimmable then you can still try using a rheostat and they will normally dim a little bit before blinking out. Lower voltages won't damage the diodes. Depending on the quality of the bulbs the dimming may not be uniform across the dash.
Please post back for others with how you make out, including the bulb brand, description, rheostat used and how happy you are with the lighting and dimming.
Similar wedge bulb bases are used in later dashes and instrument clusters with a rheostat dimmer as well as some 90 degree twist base bulbs and some grossly expensive and proprietary bullet socket bulbs. For wedge bulbs, 5 watts are often specified by Volvo as the originals in dimmable dash lighting, while 3 watts are often listed as the fitment in the aftermarket, the same bulb listed as the fitment for the (non-dimmed) door marker lights which are spec'd by Volvo as 3 watts.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now
|
|
-
|
|
|
Final Report:
Weather cooperated enough, i.e. heavy rain washed the salt off the roads, for me to do a nighttime test. I'm really happy. Lighting is perfect brightness, nice green glow allows me to read all instruments perfectly and not too bright to distract my vision. Don't need a dimmer.
Again, used the T10 LEDs noted above, placing them in the original sockets after widening the contacts to accommodate the thicker (not wider) wedge bases, Only odd man was the clock. That used a different type of bulb, so I snipped it off and then cut down the bulb barrel on the back of the clock by 1/4". Using one of the sockets I bought, also detailed above, allowed the LED to bottom in the barrel and the rubber part of the socket to fit snuggly around the outside. The hot pigtail socket wire was grafted onto the snipped red lead and the grounding pigtail got a female spade connector and was attached to the terminal on the back of the clock case.
Probably should have used a smaller LED that actually extended into the clock case, but I can read the clock, though it isn't as bright as the others, so, for now, if it ain't broke...
|
|
-
|
|
|
Way to go!
By not using a dimmer we’re you able to go with the original chassis ground system?
|
|
-
|
|
|
Sorry, Chris. Just saw your question. Yes, as mentioned, other than the clock, all of the bulb socket have an external ground contact which touches the barrels into which they are inserted. So, no dimmer meant no additional round wiring required.
|
|
-
|
|
|
Ah-ha. I never tried it without the dimmer in the loop. (Using 5W bulbs I found the dimmer has to pretty much be turned up full blast so wiring it up with a dimmer in the loop probably was a waste of time and money.)
|
|
|
|
|
©Jarrod Stenberg 1997-2022. All material except where indicated.
All participants agree to these terms.
Brickboard.com is not affiliated with nor sponsored by AB Volvo, Volvo Car Corporation, Volvo Cars of North America, Inc. or Ford Motor Company. Brickboard.com is a Volvo owner/enthusiast site, similar to a club, and does not intend to pose as an official Volvo site. The official Volvo site can be found here.
|
