Bench testing LCD clock

FRporscheman · 11-03-2009, 07:54 PM

I did a search but didn't find anything. Can someone tell me how to bench test an LCD clock from a late 944? I found an old one in my garage and I don't even remember if it was good!

If I had a late 944, I would plug it into the dash to test it, but I don't...

FRporscheman · 11-04-2009, 09:33 PM

What I need to know is which terminal gets +12V, which terminal gets ground, etc. There are 4 terminals... I'm guessing two of them are + and - to continuously run the clock, and the other two are for the screen and light...?

Charlie · 11-05-2009, 12:05 AM

The best I recall looking at the back of the clock the bottom right connector is ground, diagonal or upper left is constand 12v. The one above the ground or upper right is 12v from gauge illumination (light switch on) and the bottom left is 12v from the ignition switch. So to check the clock looking at it from the back use the bottom right ground and upper left for 12v.

FRporscheman · 11-05-2009, 03:32 AM

Thanks Charlie. I want to try that, but is there any risk in damaging the clock (in case you are wrong)?

Charlie · 11-05-2009, 10:22 AM

Please wait and I will try to double check. Somewhere I have a drawing I made of the connectors because I had to modify the bulb (circuit board problem) when I would turn the ignition or lights on the display would go blank. The way my brain works I could have this wrong or reversed.

I do remember on the back of the clock there is brown(ground), violet(gauge illumination), green(ignition 12v), red(12 v). You are looking for where the red and brown go to check the clock. Once you know where the ground is then the other 3 can have 12 volts applied. One will make the clock work the other 2 will light the bulb.

I will try to find my drawing, the more I think about it I think the ground was upper right looking at the back of the clock, just not sure.

FRporscheman · 11-05-2009, 11:08 PM

Thank you, I appreciate your help.

Two of the terminals on the back actually have a "+" and "-" sign next to them. Would the terminal with the "-" be the ground?

I thought one was for running the clock (constant 12V), one was to activate the screen so you can actually read the clock (ignition) and the third one was for the bulb? But I'm just guessing; I don't really know.

Brian Broderick · 11-06-2009, 12:59 AM

Terminals to clock

30=battery power (with just this power connection, you get no display but it keeps time)
58 =light switch (backlight)
15=ignition power
31=ground

Charlie · 11-06-2009, 01:09 AM

OK, I found my drawing and assuming it is correct the ground (looking at the back of the clock) is the upper right terminal, the bottom left is 12V to run the clock.

FRporscheman · 11-06-2009, 03:36 AM

Cool, thanks Charlie and Brian! Now I can find out if this clock works.

FRporscheman · 11-08-2009, 09:44 PM

the clock is broken...

Thanks for the help fellas.

I guess I can toss it into the projects bin. Maybe I can put a new clock into this broken one's enclosure or something.

CPR · 11-08-2009, 10:28 PM

Did you connect just 2 wires (+ and -)?

If so it will not work....the 12v (+) constant is for memeory, not for display. To test:

ground your ground wire - (should be brown IIRC) then you can twist ALL the power wires (15,58,30) together and apply the 12v + charge.

Charlie · 11-08-2009, 11:07 PM

I only have two wires hooked up on my 87 clock and it works fine. I have the bulb wired to the cigarette lighter bulb and the other two wires disconnected. The two disconnected wires go to the light switch and the ignition switch. From this I would assume the constant 12V and ground make the clock work.

CPR · 11-09-2009, 01:01 AM

gotcha...maybe mine is an aftermarket or something. I had to use at least two of the power wires (illum/12+). No telling with this thing!

FRporscheman · 11-09-2009, 06:42 AM

I applied power to the two left terminals, which I think were 30 and 15, and I grounded the bottom right terminal which is the one with the "-" next to it, terminal 31. I got a couple of "sticks" on the LCD to turn on, but it didn't show anything intelligible. I figured the screen is broken.

11-03-2009, 07:54 PM	#1
FRporscheman Addict Rennlist Member Join Date: Jun 2004 Location: Bay Area & Central Coast, California Posts: 7,345	Bench testing LCD clock I did a search but didn't find anything. Can someone tell me how to bench test an LCD clock from a late 944? I found an old one in my garage and I don't even remember if it was good! If I had a late 944, I would plug it into the dash to test it, but I don't... __________________ Arash '95 968 - '93 968 - '84 944 '82 300TD 964 stolen from San Francisco: black / red interior. So fast my wheels can't keep up.

11-04-2009, 09:33 PM	#2
FRporscheman Addict Rennlist Member Join Date: Jun 2004 Location: Bay Area & Central Coast, California Posts: 7,345	What I need to know is which terminal gets +12V, which terminal gets ground, etc. There are 4 terminals... I'm guessing two of them are + and - to continuously run the clock, and the other two are for the screen and light...? __________________ Arash '95 968 - '93 968 - '84 944 '82 300TD 964 stolen from San Francisco: black / red interior. So fast my wheels can't keep up.

11-05-2009, 12:05 AM	#3
Charlie Addict Rennlist Member Join Date: May 2001 Location: Decatur, Al Posts: 547	The best I recall looking at the back of the clock the bottom right connector is ground, diagonal or upper left is constand 12v. The one above the ground or upper right is 12v from gauge illumination (light switch on) and the bottom left is 12v from the ignition switch. So to check the clock looking at it from the back use the bottom right ground and upper left for 12v. __________________ 86 n/a 87 951 Previous Porsches 77 911 83 944 86 944 87 911 88 944 92 968 94 964 C2

11-05-2009, 03:32 AM	#4
FRporscheman Addict Rennlist Member Join Date: Jun 2004 Location: Bay Area & Central Coast, California Posts: 7,345	Thanks Charlie. I want to try that, but is there any risk in damaging the clock (in case you are wrong)? __________________ Arash '95 968 - '93 968 - '84 944 '82 300TD 964 stolen from San Francisco: black / red interior. So fast my wheels can't keep up.

11-05-2009, 10:22 AM	#5
Charlie Addict Rennlist Member Join Date: May 2001 Location: Decatur, Al Posts: 547	Please wait and I will try to double check. Somewhere I have a drawing I made of the connectors because I had to modify the bulb (circuit board problem) when I would turn the ignition or lights on the display would go blank. The way my brain works I could have this wrong or reversed. I do remember on the back of the clock there is brown(ground), violet(gauge illumination), green(ignition 12v), red(12 v). You are looking for where the red and brown go to check the clock. Once you know where the ground is then the other 3 can have 12 volts applied. One will make the clock work the other 2 will light the bulb. I will try to find my drawing, the more I think about it I think the ground was upper right looking at the back of the clock, just not sure. __________________ 86 n/a 87 951 Previous Porsches 77 911 83 944 86 944 87 911 88 944 92 968 94 964 C2 Last edited by Charlie; 11-05-2009 at 10:41 AM.

11-05-2009, 11:08 PM	#6
FRporscheman Addict Rennlist Member Join Date: Jun 2004 Location: Bay Area & Central Coast, California Posts: 7,345	Thank you, I appreciate your help. Two of the terminals on the back actually have a "+" and "-" sign next to them. Would the terminal with the "-" be the ground? I thought one was for running the clock (constant 12V), one was to activate the screen so you can actually read the clock (ignition) and the third one was for the bulb? But I'm just guessing; I don't really know. __________________ Arash '95 968 - '93 968 - '84 944 '82 300TD 964 stolen from San Francisco: black / red interior. So fast my wheels can't keep up.

11-06-2009, 12:59 AM	#7
Brian Broderick Addict Rennlist Member Join Date: Feb 2002 Posts: 4,059	Terminals to clock 30=battery power (with just this power connection, you get no display but it keeps time) 58 =light switch (backlight) 15=ignition power 31=ground

11-06-2009, 01:09 AM	#8
Charlie Addict Rennlist Member Join Date: May 2001 Location: Decatur, Al Posts: 547	OK, I found my drawing and assuming it is correct the ground (looking at the back of the clock) is the upper right terminal, the bottom left is 12V to run the clock. __________________ 86 n/a 87 951 Previous Porsches 77 911 83 944 86 944 87 911 88 944 92 968 94 964 C2

11-06-2009, 03:36 AM	#9
FRporscheman Addict Rennlist Member Join Date: Jun 2004 Location: Bay Area & Central Coast, California Posts: 7,345	Cool, thanks Charlie and Brian! Now I can find out if this clock works. __________________ Arash '95 968 - '93 968 - '84 944 '82 300TD 964 stolen from San Francisco: black / red interior. So fast my wheels can't keep up.

11-08-2009, 09:44 PM	#10
FRporscheman Addict Rennlist Member Join Date: Jun 2004 Location: Bay Area & Central Coast, California Posts: 7,345	the clock is broken... Thanks for the help fellas. I guess I can toss it into the projects bin. Maybe I can put a new clock into this broken one's enclosure or something. __________________ Arash '95 968 - '93 968 - '84 944 '82 300TD 964 stolen from San Francisco: black / red interior. So fast my wheels can't keep up.

11-08-2009, 10:28 PM	#11
CPR Addict Rennlist Member Join Date: Jul 2008 Location: Right of the Wrong Posts: 2,651	Did you connect just 2 wires (+ and -)? If so it will not work....the 12v (+) constant is for memeory, not for display. To test: ground your ground wire - (should be brown IIRC) then you can twist ALL the power wires (15,58,30) together and apply the 12v + charge. __________________ Originally Posted by ehall "This is the tech board. You should have just said that your tech problem was that you are a big dumbass. Then we could have helped you troubleshoot the way you screwed up a perfectly good turbo!" Originally Posted by JohnKoaWood "...if boost were crack, I be a full blown crack whore"

11-08-2009, 11:07 PM	#12
Charlie Addict Rennlist Member Join Date: May 2001 Location: Decatur, Al Posts: 547	I only have two wires hooked up on my 87 clock and it works fine. I have the bulb wired to the cigarette lighter bulb and the other two wires disconnected. The two disconnected wires go to the light switch and the ignition switch. From this I would assume the constant 12V and ground make the clock work. __________________ 86 n/a 87 951 Previous Porsches 77 911 83 944 86 944 87 911 88 944 92 968 94 964 C2

11-09-2009, 01:01 AM	#13
CPR Addict Rennlist Member Join Date: Jul 2008 Location: Right of the Wrong Posts: 2,651	gotcha...maybe mine is an aftermarket or something. I had to use at least two of the power wires (illum/12+). No telling with this thing! __________________ Originally Posted by ehall "This is the tech board. You should have just said that your tech problem was that you are a big dumbass. Then we could have helped you troubleshoot the way you screwed up a perfectly good turbo!" Originally Posted by JohnKoaWood "...if boost were crack, I be a full blown crack whore"

11-09-2009, 06:42 AM	#14
FRporscheman Addict Rennlist Member Join Date: Jun 2004 Location: Bay Area & Central Coast, California Posts: 7,345	I applied power to the two left terminals, which I think were 30 and 15, and I grounded the bottom right terminal which is the one with the "-" next to it, terminal 31. I got a couple of "sticks" on the LCD to turn on, but it didn't show anything intelligible. I figured the screen is broken. __________________ Arash '95 968 - '93 968 - '84 944 '82 300TD 964 stolen from San Francisco: black / red interior. So fast my wheels can't keep up.