Temp. mod resistor

[mikeWalsall]

eBay was a minefield trying suss out a compatible resistor as needed in the temperature gauge modification ... although I only need one, are these OK..??

http://www.ebay.co.uk/itm/5x-100-ohm-10 ... 0732550065

So I have looked on the Maplin site for a 100 ohm 2watt resistor .. there seems to be several listed .. but at various watts .. like this ..

http://www.maplin.co.uk/3-watt-wirewoun ... cification

The staff in my local Maplins are about as clued up as me .. I am quite sure if I ask for a 100ohms ..2 watt resistor I will get blank look

Will the above 3watt one be OK ... or as anyone got a Maplins item number that will do the job ..

[Northern Bongolow]

have you seen this link mike.
http://igmaynard.co.uk/bongo/forum/view ... hm#p556824

[corrour]

I used a 1w to do mine 4 years ago and never had any probs.
It was great to have a proper gauge not one that moves on self destruct.

[mikeWalsall]

have you seen this link mike.
http://igmaynard.co.uk/bongo/forum/view ... hm#p556824

Thanks .. I have just read it .. when removing the dash to replace the ABS bulbs .. I was hoping just to follow the simple tutorial ..

http://www.g8dhe.net/bongo_images/Tempgauge.pdf

Rather than buying loads and waiting for an eBay delivery .. I was going to pop into Maplins tomorrow (Saturday) ...

Knowing our local stores lecky expertise .. I'm just a bit wary if they can sort out a compatible resistor ..!!

[Northern Bongolow]

when i looked into this a few years ago and did mine and all my friends bongo's, i found that using the method in the link shown it tended to be a little unreliable, the method works well if you can manage to do it, most go ok, but some of the gauges get damaged during the process.
the best way i found to do it was NOT to unscrew the gauge from the clock cluster at all, this is because the screws that hold the gauge to the board (the mounting posts) can spin, and as the wires are soldered to the posts this rips them off causing a broken circuit.
far better and more reliable to get a 100ohm resister and bridge across the the TU post and earth post, this is done at the outside/rear of the gauge so its easy to swap out or uprate later if you want to play around with the values.
also in my opinion there is no need to cut out the zenner diode and replace with a bridge piece, this again makes it less obtrusive etc.

my info was obtained from a guy who used to build this sort of gauge so had a little knowledge on the matter.
mine and several others have all been reliable but i did meet one bongo that no matter how many resistors or indeed gauges would not read correct, and i never resolved the issue, all i know is it had an electrical fault else ware that was affecting things.
the temp gauge itself is a real delicate bit of kit and is easily trashed, mess with it at your peril. i know i trashed 4-5 in the process,all in the interest of learning though.

[mikeWalsall]

Thanks .. nice info .. I think I will go with your observations and just fit the resistor and leave the zenner diode alone ..

[mikeWalsall]

Fitted a 100 ohm 3watt ballast resister today .. (I left the Zenner diode in place) ..



With a cold engine and the ignition on, the Temp gauge needle is higher .....



... than it used to be ..



Is it worth pulling the needle off .. and relocating it on the square start block ..??

[rita]

I would leave the needle as it is,did you bridge Out the Zener Diode.?

[mikeWalsall]

................also in my opinion there is no need to cut out the zenner diode and replace with a bridge piece, this again makes it less obtrusive etc.

my info was obtained from a guy who used to build this sort of gauge so had a little knowledge on the matter................

Thanks .. nice info .. I think I will go with your observations and just fit the resistor and leave the zenner diode alone ..

No I did not bridge or remove the diode ..

[Northern Bongolow]

ive never tried a 3w, ive used lower ones (single) or 2 smaller still in parallel, so maybe this is the issue,ive not seen one the give results you see.

[mikeWalsall]

When turning the ignition on the temp gauge goes up to around 10 o'clock then stays there ... it does not move up or down even when the engine as fully warmed up ..

I thought the 'magic' bit was the 100 ohms resister .. the wattage just the margin of safety ..

I also assumed that a ceramic / silica ballast resister would be better than the cheaper foil type .. ??

[Driver+Passengers]

My first thought was a "floating" input, or poor earth, or something. I haven't checked the wiring diagram or circuit diagram to make sure you've done the mod correctly, but worth checking the temp sender on the front corner of the head.

One way you could get some numbers from it (though I've not checked what the numbers should be...)

[While cold]
1. Remove connector, measure resistance from tip of sender to ground.
2. Replace connector, measure voltage from tip of sender to ground. [with ignition on]

[When hot]
3. Leave connector in place, measure voltage again [with ignition on]
4. Remove connector, measure resistant from tip of sender to ground.


If all checks out, then a continuity check from the sensor connector wire to the dash unit.

[mikeWalsall]

Although to my reckoning previously the needle as always 'sat' a bit low (well down from the square 'start' block) but the temp gauge as always worked OK ... usually getting up to 10-30 - 11 o'clock

I thought as I had the dash out for other work I may as fit an 100 ohm resistor to 'damp' the gauge ..

Now when turning on the ignition the needle goes up to around 10 o'clock .. even with the engine 'hot' it barley moves ..

Maybe that is how the mod works ... and the damped gauge is working as it should ..??

[Driver+Passengers]

I don't believe so...

Mine starts moving at 65 degrees and the fans come just past the thick-tick at the right hand side. 75-85 represents 12 o'clock to 1 o'clock on my guage.

I know there are a couple of animations of expected behaviour of the needle under different mods.

I think that whatever is going on, having a cold steady-state giving you a reading on the needle that is not on the bottom stop and barely any movement when hot is not right. My needle will respond visibly to a hill climb, for example.

[Edit - electrically, I'm not sure what the zener diode does - but I think I bridged mine.]

[mikeWalsall]

Just got back from the MOT .. I got there with an 'hot' engine and the tester kept the engine running for quite a time while doing the (power) steering .. exhaust .. emission tests .. I looked at the temp. gauge several times, and the needle was rock solid, not budging even when the rad. fans kicked in ..

As it only a takes couple of minutes to remove / replace the clocks .. I will live with it for a week or so .. then either have another look .. maybe short out the diode ..maybe fit a Masons .. or just put it back to original ..