Speedometer not working
Le Mans Master
Joined: Mar 2011
Posts: 6,835
Likes: 301
From: Columbia SC
Ok Dadaroo and lionlhutz I have my speedo back.
Took it all apart just nudged the needle and were back in business.
It's amazing how much faster breaking it down and reassembling it went the second time.
Getting to know my vet inside and out.
Thanks again for your knowledge and help
Casamero
Took it all apart just nudged the needle and were back in business.
It's amazing how much faster breaking it down and reassembling it went the second time.
Getting to know my vet inside and out.
Thanks again for your knowledge and help
Casamero
Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
Good to hear it was just that simple. Makes me wonder what made it stick like that.
I don't consider it to be analog because an analog signal would be something like 0-10V with the varying voltage representing 0-200mph.
I don't consider it to be analog because an analog signal would be something like 0-10V with the varying voltage representing 0-200mph.
Le Mans Master
Joined: Mar 2011
Posts: 6,835
Likes: 301
From: Columbia SC
10-4, I am satisfied to just understand the interface regardless of what it may be called. I am still puzzled at why the Tach interface was done differently. Probably due to how the inital signal is generated. Oh well, thanks for working with me on this one. I am still on a learning curve.
Melting Slicks
Joined: Aug 2003
Posts: 2,786
Likes: 7
From: Iowa
Thanks, McGilles, I figure the pulse method also somewhat does the same thing that voltage limiters did in the "old days" to limit needle movement due to voltage changes. What puzzles me is my FSM says the Tach uses a serial bus signal. Go figure?
PS: Do you consider the pulse to be a digital signal? I don't, but it just may be symantics. I think of it as a pulsed analog voltage signal no different that what made the old rotary dial phone systems work by stepping relays at the other end.
PS: Do you consider the pulse to be a digital signal? I don't, but it just may be symantics. I think of it as a pulsed analog voltage signal no different that what made the old rotary dial phone systems work by stepping relays at the other end.
usually when someone says digital I think of simply on/off discretes for something like serial data, the speedo and tach signals are neither really, their just pulses. but if it had to be labeled as digital or analog as the only options, its definitely a digital signal. the only voltage you will find on that wire is B+ or ground.
Le Mans Master
Joined: Mar 2011
Posts: 6,835
Likes: 301
From: Columbia SC
Thanks McGilles, found the pulse Tach wire on the Red C2 connector in the FSM. Searched everywhere but could not find info on the 2 pulses per rev. I believe you, I am just curious where they hid the info. In the IPC discussion, the Tach and Speedo are discussed side by side. The pulse info is there for the Speedo, but they only say the Tach signal is serial bus.
PS: Can you clarify what B+ means? I would think this is whatever the battery voltage is.
PS: Can you clarify what B+ means? I would think this is whatever the battery voltage is.
Melting Slicks
Joined: Aug 2003
Posts: 2,786
Likes: 7
From: Iowa
Yes, I noticed that also! I found the spec for the tach pulse elsewhere. It is published on web sites that sell aftermarket tachometers and shift lights, because for LS1 vehicles they have to be configured for 4 cylinder mode. aparently the typical tach pulse gets a pulse for each ignition, which means a standard V8 should be 4 pulses per rev, but the LS1 PCMs are different, they do 2PPR for some reason so aftermarket shift lights need to be set for 4 cylinder mode to turn on at the right time. as far as I can tell all LS1 powered cars are set up this way. no idea why!
B+ is indeed the positive battery voltage, I don't have a clue where that name came from, but that's what I've always heard it called. It makes more sense than calling it 12V because a car's 12V is not 12V when the engine is running. Wiki says B+ is simply an abbreviation for "battery positive" I guss that makes perfect sense!
B+ is indeed the positive battery voltage, I don't have a clue where that name came from, but that's what I've always heard it called. It makes more sense than calling it 12V because a car's 12V is not 12V when the engine is running. Wiki says B+ is simply an abbreviation for "battery positive" I guss that makes perfect sense!
