Disassemble tacho

[deverett]

I'm currently fitting green led lighting inside the gauges in my dash (S2) and I am struggling to get the tacho apart. The other gauges are easy, but with all screws removed the insides are still not budging. The number on the tacho is 4784 if that helps. Hopefully someone has pulled one apart, I'm concerned about applying too much force, if that is what it needs.

Attached is the speedo lit up with the led strip inside. I plan on detailing where to get the parts and do the work here when it's finished.

Thanks,

Dave

[Gis]

Don’t apply force. I pulled mine apart a while ago for the same reasons. I remember there were folded edges on the outer front ring that held the casing together. Pry those edges back carefully and the speedo will come apart. You can see the folded edges in the picture of the rpm gauge below. It’s the same principle

[snowrx]

If you've not yet considered dimming, here's what I did.

https://www.lotustalk.com/forums/f164/pwm-dimmer-g-car-dash-led-s-356713/

 

I had not thought of using internal strips, I just made some screwbase with 5730 LEDS in the original lamp holders. One could go wild with some RGB strips........

[deverett]

Thanks everyone. The issue is not the glass or bezel, those are easy to get off, you just twist to line up the cutouts. The issue is the internals. All the other gauges come apart fine, the tacho is rock solid in there and I'm not certain what that is due to.

I did try led bulbs originally but the design of the lighting makes it worse as the led bulbs tend to use leds that point forward, while an incandescent bulb emits light all around the bulb. This leads to even darker corners. I imported my Esprit from Wales, so the speedo is in MPH and the KPH figures are smaller and in the dark more. When approaching a speed camera at night it was a struggle to work out my speed in KPH. Now I can see all numbers evenly, except for the odometer which is even brighter (I might have to put a shade behind it).

Dave

[snowrx]

I made the two on the right from screw shells and T10 LED wedge bulbs so they would shine all directions inside the gauge.

[Gis]

2 hours ago, deverett said:

Thanks everyone. The issue is not the glass or bezel, those are easy to get off, you just twist to line up the cutouts. The issue is the internals. All the other gauges come apart fine, the tacho is rock solid in there and I'm not certain what that is due to.

I did try led bulbs originally but the design of the lighting makes it worse as the led bulbs tend to use leds that point forward, while an incandescent bulb emits light all around the bulb. This leads to even darker corners. I imported my Esprit from Wales, so the speedo is in MPH and the KPH figures are smaller and in the dark more. When approaching a speed camera at night it was a struggle to work out my speed in KPH. Now I can see all numbers evenly, except for the odometer which is even brighter (I might have to put a shade behind it).

Dave

As long as you have the glass and bezel off at the front as well as all the screws out at the back, it should slide out. Didn’t have any issues with mine. Don’t know if the pic helps but that’s how the tach looks like when it’s out

[deverett]

Actually you have the speedo in your hand. That came apart fine for me. The tacho has a clear green sleeve that takes the light, 2 mounting screws and holds the connector.

[Gis]

2 hours ago, deverett said:

Actually you have the speedo in your hand. That came apart fine for me. The tacho has a clear green sleeve that takes the light, 2 mounting screws and holds the connector.

You are right Dave. My bad. I didn’t disassemble my tach as there was no reason to do so. Just cleaned up the front glas. Forgot that actually. Sigh. Looking at yours, the only thing that seems to hold the insides in are these bolt plastic sleeves, one is loose, the other is tight. Work it gently, there must be a way. No additional screw under that sticker I assume?

[Steve4012]

Dave, this is the tacho on my '81 turbo. After all the screws are removed and glass out it just falls out. As mentioned, check there isn't another screw under the sticker, otherwise it seems the green plastic cover maybe holding it in place. 

[deverett]

Man, I wish my tacho was the same. It definitely seems to be glued in there.

Gis, that screw is loose because I started tapping it with a rubber mallet to see if it was holding things together, it moved in about 10mm but the internals did not move. I pulled it back out and the plastic sleeve was still up as I had not reseated it yet. I'd cut this case open if I had a spare tacho, but that seems more crazy than usual for my work. I have a fireoptic camera i will try and stick inside in the next few days. That might answer some questions. But at present I'm back to using a bulb. For the tacho, the bulb can only go halfway in and the holder shrouds the other half so the light does not leak into the dash. I really want to fit LED strips as they are working out great on all the other instruments. The dash mounted dimmer also works with them.

 

Dave

[Steve4012]

Can you give details of the led strips please Dave? 

[deverett]

Yes, I ordered the strip from Banggood.com.:

https://www.banggood.com/5M-5054-Pure-White-Warm-White-Red-Green-Blue-Pink-Ice-Blue-Non-waterproof-600LEDs-Strip-Light-DC12V-p-1203436.html?rmmds=search&ID=225&cur_warehouse=CN

I see at the moment they are out of stock of green, but you could probably find it on ebay as well. 5054 led strip 12v.

You can cut the strip in segments of 3 leds. Each LED has a current resistor, so you don't need to do anything else. On the cut points are solder pads so you can connect up small pieces to wire. I will run these in parallel through the dash dimmer. I have a lot of LEDs in the speedo, that strip draws about 600ma. Which is still probably less than the incandescent bulb I had in there before.

I bought some agressive le sided tape. The tape that comes on the led strip is very thin and there are electrical contacts on the back so I didn't want it to short on the metal of the instruments. The Voltmeter is shown there with about 6 leds (2 segments). I used only 3 on the other small instruments since light can only come out through a hole at the top and shine downward onto the scale and needle.

 

[Gis]

15 minutes ago, deverett said:

Man, I wish my tacho was the same. It definitely seems to be glued in there.

Gis, that screw is loose because I started tapping it with a rubber mallet to see if it was holding things together, it moved in about 10mm but the internals did not move. I pulled it back out and the plastic sleeve was still up as I had not reseated it yet. I'd cut this case open if I had a spare tacho, but that seems more crazy than usual for my work. I have a fireoptic camera i will try and stick inside in the next few days. That might answer some questions. But at present I'm back to using a bulb. For the tacho, the bulb can only go halfway in and the holder shrouds the other half so the light does not leak into the dash. I really want to fit LED strips as they are working out great on all the other instruments. The dash mounted dimmer also works with them.

 

Dave

Got it Dave. I made an external adapter ring for mine to be able to set back the (longer) led bulp and compensate for its extra length, then I used one of the existing external screw/screw holes to secure it in place. Worked well. Could be a workaround for you. I did not want to disturb the tach internals.

[deverett]

It's worth a try mate, I'll give it a go.

Thanks,

Dave

[Steve4012]

That's really good info on the led's Dave many thanks. 

Steve.