LED Bulbs in HVAC

[steve118]

i just replaced the dim green covered bulbs in my A/C - fan - heater control unit (HVAC?)

but none of the lights work, i have reversed the bulbs thinking it was the polarity +/- that was the issue. but nothing, and the bulbs work when connected to a battery.

are they not getting enough power or too much power? kinda stumped on this one...

all wire connections are the same btw.

[nickch]

EDIT: whoops.. just read that it was LEDs..

Polarity is important yes. Reverse them if they don\'t light up at first.

Most automotive LED bulbs should have reverse polarity protection diodes.

bulbs work on battery: 12V battery?

Power draw shouldn\'t be an issue. Do you have a multimeter handy?

Check what voltage at the connectors.

[Rosssub]

I would guess that the HVAC Bulb/Output is only about 6v? With 12v LED\'s installed it wont be enough Power. That\'s why they glow on the Battery 12v.

[Rosssub]

Looking in this thread, the 4mm LED\'s run on 9-14.4v.

http://www.clubsub.org.nz/forum/index.php/topic,41792.0.html

LED Specs:

http://www.superbrightleds.com/products/led-products/220,221/

[steve118]

 Rosssub said:

Looking in this thread, the 4mm LED\'s run on 9-14.4v.

http://www.clubsub.org.nz/forum/index.php/topic,41792.0.html

LED Specs:

http://www.superbrightleds.com/products/led-products/220,221/

ahh yip that\'s my first one, i found some 3mm LED bulbs at jaycar and the guys said they would work fine etc as they were low voltage LED\'s?

these are the ones i bought: http://www.jaycar.co.nz/productView.asp?ID=ZD0130&w=3mm+LED&form=KEYWORD

am i also right in saying that the lights would be in parallel? so if one was not working, the others should still work? not like the old days of \'if one bulb is out, they all go out\'?

[Rosssub]

 steve118 said:

am i also right in saying that the lights would be in parallel? so if one was not working, the others should still work? not like the old days of \'if one bulb is out, they all go out\'?

I would guess each Bulb is powered by it\'s own Function/Source through the Circuit Board. Like Dash Lights/Warning Lights etc. (haven\'t had one apart yet)

I\'d still test the Output Voltage at the Bulb Contacts when turned on. Also with the Head Lights on, or HCAV Display Dim on. Assuming a Switching/Variable Resistor Power Source, linked for all Bulbs.

Also test both contacts for one Bulb, with a separate earth. To make sure the OEM Bulbs are +/-. Maybe a Polarity issue, ie, both contacts are live, earthed through Switch. Or both Bulb Contacts are Earth, powered through Switch.

[hijacka]

Do the leds have a resistor? Some of the plug in or direct replacement bulbs the tabs are shitty and you will general need to bend and move them to get them to make contact they will general have a resistor , if you just have a bear led bulb then you will need a resistor you can go to jaycar or why to find the right ohms. if you don\'t get that right then you will blow bulbs eventually. yes polariy is important