Skip to main content

*I’ve been enjoying and benefiting from the discussions on this forum for years now, but have remained fairly quiet in part because I wanted to have something of value to add to the conversation.  Hopefully this post will be useful to someone and the first of many contributions to come*:

There’ve been other discussions over the years about gauge backlighting, I thought I’d resurrect the topic and add my own update.  It seems the dim lighting of the incandescent BA7S bulbs is a common problem.  I found that I could barely read my speedo at night, which at minimum is clearly a safety issue, and not an optimal driver experience.  Btw I have 914 gauges but my understanding is that 356 gauges have the same problem.  I experimented with a few different LED solutions, here’s what I concluded:


OSRAM 12V 2W bulb standard BA7S:

My original incandescents.  You already know:  Very dim, let’s move on.


The “Jules Dielen” LEDs:

These are my top choice.  They’re ~0.23 Watt (my original incandescents are 2W) and 2400K color temp (so they have the same color temp as originals as you can see in the comparison photo), and brighter than my original incandescents.  I have to admit, they’re still not super duper bright, but they are clearly significantly brighter and absolutely worth it in my opinion.  

Jules mentioned that these LEDs have super lifetime, in fact, he’s got one or more connected to a 12V source in the garage for the past continuous 5 yrs and they’re still going strong.  They’re LED after all.

As you can see in the photos, he also provides them with green or blue lens for your fog or high beam indicators.  I think this because the bright white light of these LEDs could overpower and wash out the builtin gauge color filter, I don’t think this happened to my gauges, but might as well get the corresponding colored LEDs anyway.

As you can see in the photos, the LED is mounted on the nose of the package.  So it mostly illuminates axially (straight out the nose), as opposed to radially (side ways).  Still, they’re bright enough to illuminate sideways and thereby light up your gauge face.  This is also notable for the 914 combi gauge, where the back light also has a corresponding indicator window on the face, so that always lights up and doesn’t seem to serve any other purpose AFAIK, but it’s fine.  For the 356 gauge, the equivalent might be the green indicator that’s between the blue high beam and red battery indicators.

Who’s Jules Dielen?  A very kind, knowledgeable, and helpful gentleman that I was pointed to by one of the well-known speedo repair shops.  He’s a 356 owner who decided to design LEDs because there wasn’t anything decent commercially available, and simply started offering them to community members because a demand developed.  So he’s not out for profit, but instead a helpful community member.  If you want his contact info, feel free to PM me, I just didn’t want to put it on blast.  

Lastly, I think what he charges is more than reasonable, especially considering the low volume specialized production.


BA7s LED Bulb from


These are also pictured in the attached photos.  I’d say they had similar brightness to the Jules Dielen’s LEDs.  However, at 6500K, they’re clearly cooler/bluer in color temp.  I thought they were too cool/blue for this classic car, it didn’t match, and so I was much happier with Jules Dielen’s LEDs.  While on the topic of color, they also come in green or blue.  

Lastly, they’re very very affordably priced, but again, to me it didn’t matter if they were free.  So I’m just holding on to them as replacements to the incandescents of the indicators…  Speaking of, I kept my turn signals as incandescents because I enjoy the classic fade in/out effect.  But, if you don't mind the color, these are a great and cheap option.


Few options from (aka

I never tried any of these, but including my experience for completeness' sake.

Another thread mentioned the Inverted Ba7s, which have an inverted lens to promote radial / sideways illumination, which is what you’d want for a backlighting LED.  Search the page for these.  However, from that vendor, “The inverted are not very bright”.  Further, they said that they no longer have any in stock and don’t plan to restock because they don’t sell well.  Therefore, I never tried these.

The vendor suggested their “Covered 1 Watt Ba7s 3898 Instrument Panel Gauge Colored Led Bulbs Lights Lamps”, see .  They said “These are also very bright and illuminate in a wide pattern”.  I didn’t try these because I was already happy with Jules Dielen’s LEDs, and I’d already learned that 6K color temp is way too blue based on the SuperBrightLEDs bulbs.

The vendor also suggested their “5x 5050 Ba7s T5 Instrument Panel Gauge Colored Led Bulbs Lights Lamps”, see .  They said  “If you have room for the enlarged heads, the 5x 5050 will light sideways and is very bright.”  I don’t doubt that these illuminate radially based on the side-mounted LEDs.  BUT, they’re 11mm in diameter (too wide for my gauges) and still have the blue color temp problem.



In both attached gauge photos, I compare Jules Dielen’s LEDs (always on the right side of the gauge) to the white/bluish SuperBrightLEDs (on the left) and my original incandescent bulbs (on the left).  You’ll know which is which.  Obviously, these things are hard to capture in photos, but I did my best to capture an accurate comparison.  All that ambient red light is from the taillights reflecting in the garage, I’m not in Amsterdam!

In the bulb closeups, leftmost are Jules Dielen LED, middle is SuperBrightLEDs, and rightmost bulb is my original incandescent bulb.


Misc Info:

• Mine are the BA7S (aka BA-7s) bulb standard, not to be confused with the similar but different BA9S.  I think BA7S stands for Bayonet 7mm Single (as opposed to Dual bulb/terminal like those larger bulbs in our taillights). 

• I’ve come across talk about polarity, i.e., making sure each of yours are either center positive or negative.  In my case, everything was center positive.

• Someone at one of the other well-known speedo repair shops not to be named, warned me that LEDs’ heat would cause damage to the gauge face or something like that.  I thought this was odd but kept an open mind because sometimes LEDs can be hot contrary to common belief.  That said, the LEDs I tested were significantly cooler (in degrees not color temp) wrt the original incandescent bulbs…

• Other search keywords for posterity:  Tachometer, speedometer, odometer.



Images (4)
  • SuperBrightLEDs vs Jules Dielen
  • Incandescent vs Jules Dielen
  • Jules Dielen, SuperBrightLEDs, Incandescent
  • Jules Dielen, SuperBrightLEDs, Incandescent
Original Post


Sean, thanks for this useful stuff.

It seems nothing is simple about our crazy cars - even instrument lights. I found this out early on.

As you point out, standard instrument bulbs are usually two watts. But in a hand-made car put together in a custom shop, nothing is necessarily 'standard'.

Like a lot of our replicas, my car came with Chinese copies of the original VDO gauges. For some reason, the instrument bulbs were five  watts each. And there were six  of them. Maybe someone noticed the 2-watt bulbs were too dim and decided 5-watt bulbs would be better. Well, they WERE brighter.

But 30 watts of lighting is a lot for instruments. That's more than half as bright as a standard headlight bulb. They were way too bright and needed to be dimmed quite a bit. For which you'd naturally use the instrument dimmer in the headlight switch, right?

In my car, that turned out to be a good solution. For about three minutes.

Then, there was a lot of smoke.

Eventually, I ran the numbers and figured out what was going on. It turns out that if you want to dim 30 watts worth of incandescent lighting to, say, one-quarter brightness, you've got to dissipate over 20 watts of power in whatever is doing the dimming. My Chinese headlight switch wasn't close to being up to the task. Nor are most electronics rheostats (or 'potentiometers' - 'pots' for short) that are usually rated at about two watts. I ended up building a little circuit out of ceramic 'load' resistors and mounting them to the steel crossmember under the dash as a heat sink.

I should have tried to find the bulbs you describe, but didn't have the moral courage or fortitude for the hunt.

As it turns out, a lot of people with these cars have had headlight switches burn out - literally 'burn' out. I'm pretty sure it was the dimmer circuit that was responsible in many cases, not the main headlight contacts in the switch. Of course, it's still best practice to keep heavy current away from any of these switches by using relays that are designed to do that.


Thank you Sean. Great information.

the green, red and blue LEDs where excellent for the blinker, oil pressure and high beam warning lights,

I did a similar retrofit years back.  I ended keeping one regular incandescent background lighting bulb in each gauge.

 Why you may ask?

I found that on chilly mornings and winter time ( with and without the top up/ hard top on) the gauges would fog up when all my bulbs were LEDs.... the little bit of heat from one incandescent bulb In each gauge was enough to keep condensation at bay.

Great write up.


@Sacto Mitch thanks for adding that to the conversation, I hadn't considered higher wattage incandescents, and I'm glad I hadn't because I probably would've gotten pulled in and perhaps not experimented with LED solutions.  You're right, that's a lot of wattage whereas the LEDs add up to a whopping grand total of ~1W!  If nothing else, at least I have a little more time to discover I left the lights on before my battery dies!  I did the upgrade so the headlights buy me more time too (which might be the topic of another future post...)

@Lfepardo thanks for another great addition to the convo.  Being in California, I didn't think about that, if anything we have the opposite problem over here!

@MusbJim@edsnova@Michael B (aka bluespeedster SoCal), it was my pleasure, and if anything I should be thanking all you fine gentlemen (including the other "titans").

Sean, when I built my Spyder, every single bulb in the entire car installed was LED.

Headlights, turn signals, dash gauges and indicator lights, third brake lights in the grilles, and even sequential shift lights. EVERY. SINGLE. ONE.

My electrical consumption when all lights are on is nil compared to before. Also, the current running through the headlight switch is low, making everything last longer.

I was lucky, I ordered gauges from Speedhut, they came with their own dimmer harness that works on pulse-width-modulation for dimming.

The options you detailed for guys with conventional gauges are great, thank you for the informative article.

Last edited by DannyP

Add Reply

Post Content
Link copied to your clipboard.