Rheostat Bypass Question

Try posting a photo of your rheostat assembly as Ferrari wire colours are notoriously unreliable. Normally the rheostat has two wires going into them and all you need to do is circumvent the rheostat by bridging the two wires. Beyond that I am not sure why you are seeing 3 wires as part of the assembly.

 

Ron, I can't recall the colors of the wires. What I did was take the 2 wires controlled by the stat (seems like one on either end) and simply connected them together bypassing the stat completely. Worked great.

 

I thought I read some years ago here that bypassing the rheostat does not make the lights any brighter. I assume that's the reason you are doing it, to get brighter dash lights. But if if you do it and it works, let us know; they certainly need to be a LOT brighter!

 

Bypassing it won't make them brighter than their full potential (I know that sentence is obvious, but I hope it makes sense in terms of how I'm typing it), but if the dirty old rheostat is causing too much resistance (even at full volume), then bypassing it will make them brighter - as it becomes a straight circuit. In other words, a bad rheostat might only offer 0-80% output compared to the bulb's 100% potential.

Of course, you won't be able to dim your lights anymore. But I don't think anyone's interested in that stock dim OEM appearance.

 

Bypassing the rheostat will result in brighter lights. I have tested this with an NOS rheostat and it is always brighter without it.

 

do it

3 wires...b,g,n

white, (b-bianco), has power when lights are on
yellow, (g-giallo), to instruments
black, (n-nero), ground

you bypass the dimmer by connecting wires b-bianco and g-giallo

 

Let us know if there is any improvement. Many past posts on the subject have stated everything from no difference to an obvious difference. I would expect no difference unless the dimmer is faulty or the connections need cleaning. It will be interesting to see what it did for you. I have never tried it - guess I should. It just takes a couple of spade connectors on a 1" piece of wire!

 

I think that was the case with mine. It no longer dimmed; it was mainly "OFF" to "Well, the lights sputtered and came on... sort of" somewhere in the middle of the dial. I started to clean it, but in the end just bypassed the whole thing. It did get a bit brighter, but LEDs would be far more improving.

 

This is just my opinion and I should probably just keep it to my self but I’m sure there are at least a few people out there who will agree with me so here goes. I think people are suffering from oversaturation of light these days. There are some insanely bright headlights and I’m fairly convinced that if I actually look at the flashing blue and whites on a police car I would suffer irreparable eye damage they are just too damn bright. I mean I get that you want me to see you but I could see you just fine with the old lights.

So in the same sense I don’t want the instruments in my 308 lit up like a Christmas tree at night. With the OEM lighting I can tell just fine if I have gas or oil pressure and that I’m not speeding. Maybe because I’m a pilot, im just used to dim instrument lighting as being normal. Anything above what’s necessary to read the gauge is just bling as far as I’m concerned. I don’t need the guy in the car behind me to be able to read them.

Okay, rant off, my apologies...

 

Paul,

Next time you're doing your preflight check, try bypassing a few rheostats to get brighter gauges - you might be surprised at the difference. I'm sure someone will, at least.

 

Paul, I totally agree re the bright lights and I have the same problem with police lights...even when they are not after me! I would like the dash lights on my 328 to be a bit brighter but not all that much. Frankly, they are OK on a deserted road where I don't meet much oncoming traffic but there just aren't quite enough lumens there for me under typical night driving conditions with other cars on the road. Admittedly, I don't drive it at night all that much which is probably one reason it's not that big a deal. But in my recent drive from MD to TX, during the last couple of hours in the dark on I-10 between Houston and San Antonio, the gauges were so difficult to see that I could have resorted to that old flying trick - holding a penlight in my teeth! As you noted, much of the problem is all the "other" lights. Heck, modern car tailights are sometimes blinding!

So a bit of additional instrument brightness would be a good thing for me/my 328!

 

Other than changing to LED lights to get much brighter lights, one can do some basics to improve what you have.

1. Replace all the gauge lights with new ones. Don't touch the glass with your fingers so oil from your fingers will not get on the glass.

2. Clean all the male and female terminals in the connectors, as well as, the connections and jumper wires lugs on the back of the gauges.

3. Clean the glass faces of the gauges and then take a real good look to see if they are also dirty on the inside. Mine were. 39 years of dust can easily be accumulated and build up slowly. I was able to take the speedometer and tach glass off and it made big difference. (There was a post on how to replace the clock lens that details how to get the chrome ring off. This is not for the faint of heart because the plastic cases are brittle. Removing the ring can be done but it requires a light touch and patience.) You can also clean and polish the chrome trim ring with some 0000 steel wool to bring back the shine. The three smaller gauges posed a challenge because I could not get the glass off easily, so I just left them as is. If you do this, it should be noted that the clock has a plastic lens that gets cloudy and can be replaced with a glass one. (My car is a 78 308 GTS USA version) The lens is available from Verell at unobtainiumsupply.com

4. The tachometer does not have a green plastic light diffuser, unlike the speedometer, so it does not light up evenly all the way around. Its brighter on the left side compared to the right.

5. Use a jumper cable to bypass the rheostat.

6. If you do all this and even if you don't, take a drive at night and really look at the subtle beauty of the dashboard and gauges. The speedometer and tachometer needles with their turquoise border and back stripe are unique. The light and high beam indicator lights aren't just round glass, but multi-faceted and look like little colored diamonds when lit up. The subtle green glow of the lighting is my favorite color for gauges, similar to the late model Saab color. I also like the multi-colored numerals of the tachometer as you go toward redline.

6. But the most creative feature of the lighting is the green light that illuminates the heater levers on the console. That light is in the fold of the metal of the handbrake lever and shines down to light up the levers. It is a small, torpedo shaped light that has a green tint on it. (With age the green tint wears off and you loose the green glow). One of the members recently did a run of LED lights that replaces the original. Great color match with the eerie green glow. It is so cool! With all the crazy characteristics of the 308 series, Ferrari could have eliminated that light and we would all be in the dark when adjusting the levers. But somebody was thinking that day long ago. "OK. Let's take a bulb, paint it green and shove it up inside the brake handle." Damn good engineering, but how come they forgot the tachometer diffuser?

Get out at night and enjoy the ride.

 

Well I will walk my rant back a bit and admit that I do have my rheostat turned up to max so it may as well be bypassed. The only time I ever touch is is by mistake when I'm trying to reset my trip odometer.

 

I agree, but my dash lights are pathetically dim. I want just a bit more juice.

 

LED dash upgrade is one of the best things I did. Along with HID headlights, it made night driving enjoyable again. Because of my middle age presbyopia, I can't read the gauges properly during the day without reading glasses anyway, so it's actually easier at night.

 

FWIW I bypassed the dimmer on my 328 a few minutes ago and it made no difference at all vs the dimmer at max.

 

that`s all it can do

 

The silver lining is that your dimmer is working as it should.

 

Yep all the current is available! Just need more of it!