Odd HVAC display behaviour

jerrytlr · Jan 4, 2012

Hi all, just wondering if anybody has seen this before - I replaced the bulb in the HVAC display a while ago, all was fine for a couple of months but now the brightness of the display seems to vary for no obvious reason, making it unreadable at times. The really odd thing is that the brightness seems to change when you alter the temp setting, so for example if it is set to 'Lo' then you can read it, but increase the temp and it fades away so that but about 19deg you cannot read it at all.

The operation of the HVAC doesn't seem affected at all, and all the other lamps (for the temp switches, demist switches etc.) are the correct brightness.

Any ideas??

Cheers,

Jerry

zzr1200 · Jan 5, 2012

I have the same intermittent Hevac Lighting at the moment, I also had this problem about 3 years ago, ended up changing the bulbs.

I personally believe its poor quality replacement bulbs, I'm considering phoning the stealer's for a price for a complete set of oem dash bulbs.....unless someone can recommend a supplier of quality Lucas bulbs, I'm fed up buying crap Chinese copies or Ring Bulbs which are probably Chinese away these days.

Datatek · Jan 5, 2012

When bulbs fail on mine, if they are the ones mounted in plastic holders, I remove the bulb from the holder and replace them with ultra bright LED's (with a resistor to current lilmit) Red looks nice in the clock other places I use white.

Chrisfrain2007 · Jan 5, 2012

Datatek said:
When bulbs fail on mine, if they are the ones mounted in plastic holders, I remove the bulb from the holder and replace them with ultra bright LED's (with a resistor to current lilmit) Red looks nice in the clock other places I use white.

Sounds like a good plan, what resistor do you use?

Datatek · Jan 5, 2012

Chrisfrain2007 said:
Sounds like a good plan, what resistor do you use?

Depends on the type of LED and the required current. Typically a 1K ohm 1/8 watt for red.

Chrisfrain2007 · Jan 5, 2012

Will look into this a few of mine have gone

jerrytlr · Jan 23, 2012

Hi just wanted to close this thread out - I am now 99% sure that the problem was simply a failing battery causing low voltage (even with the engine running). It does seem that the HEVAC display, along with many other things on the P38, is sensitive to even small drops in voltage....

Cheers,

Jerry

Teamemmenracing · Jan 24, 2012

Well before you close it ........

I had the problem for ages, bright dim, really dim bright again, invisible .........
slid the radio out to have a look ...... a sharp rap on the back of HEVAC unit and the lights came back on full and have been for almost 9 months now.

gfromleeds · Jan 24, 2012

Teamemmenracing said:
Well before you close it ........
I had the problem for ages, bright dim, really dim bright again, invisible .........
slid the radio out to have a look ...... a sharp rap on the back of HEVAC unit and the lights came back on full and have been for almost 9 months now.

lol if in doubt give it a good clowt

Odd HVAC display behaviour

jerrytlr

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zzr1200

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Datatek

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Chrisfrain2007

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Datatek

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Chrisfrain2007

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jerrytlr

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Teamemmenracing

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gfromleeds

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