Hey, I went through the steps detailed here, with one exception: I used the VSS signal from the sensor on the trans, because I didn't feel comfortable disassembling my speedometer. The problem I have is...Any time I press the brake (or turn on the turn signal, activating the brake light) My speedometer drops to zero. It also drops to zero any time I push one of the buttons on the cruise wand (set/decrease or resume/accelerate). The speedometer also goes to 0 above 50 mph. The cruise of course doesn't work. My question is, has anyone tried this mod, and have any tips? Any help would be GREATLY appreciated.
Edit: Fiero is an 85 SE
[This message has been edited by fiero91 (edited 06-30-2015).]
You're dealing with two issues..... Issue1) If you've got the notchie, you have to use the relay method instead of hooking up to the rear lights because of the notchie combined turn/brake lights.
Issue two) double check the wiring. Sounds like something is wired up backwards. Some of the wire colors are off and you'll need to rely on the addresses on the connectors.
I tried the method you've posted and had the issue of the cruise cancelling every time I used my right turn signal. Ha ha that's when I gave in and used the relay method. I also tried to skip the step about cutting the wires at the pedals, that didn't work either ........learned the hard way. Check your wiring first.
[This message has been edited by f85gtron (edited 06-30-2015).]
I've checked my wiring, and I did use relays. All my wiring is correct as near as I can figure. Did you take your VSS signal right from the sensor wires? And does it matter which of the two wires you use?
I took my signal from the ecm output (7730), so that won't help. It does matter which line to use. One is hi and one is low. I've read that the vss signals (hi and low) are both at higher voltages than what the digi-cruise is expecting and the jury is still out on how the signal will effect the cruise logic.....hence the buffer. But even with that, it should not push current or ground The vss signal when brakes or options applied. The brake switch and the turn signals don't merge until after the brake switch, so If wired using the relay method, at no time will a turn signal current run through the brake switch. You can test all connections with a meter to make sure grounds are grounding and so on. If your wiring is good, and Unless the cruise is bad, there's no explication for the speedometer acting up. Is there any wires run to the rear lights at all?
[This message has been edited by f85gtron (edited 06-30-2015).]
No, I used relays, one to supply hot when the brake/clutch is not pressed, which switches to ground when it is, and another to supply ground when the brake is not pressed that switches to hot when it is (in the correct positions on the connector) I suppose I can try tapping the other VSS wire, but I didn't see how that should matter, unless I just happened to get a bad cruise module. Do you know if it matters what car it's from, as long as it's got the AR sticker and long cable? Sorry for being such a PITA, I didn't have problems with installing power windows, power locks, or keyless entry, but this one just has me stumped.
I just used one 5 terminal relay. 85) hook to terminal a (ppl) of vacuum release solenoid 86) ground or terminal b (blk) of old vacuum release solenoid 30) Connect to terminal G on new cruise module 87a) connect to ign b+ 87) Ground or terminal b (blk) of old vacuum release solenoid
If your confident it's hooked up right, then sounds like the cruise is bad. Any ar should work, in fact, all of them should work, just the ar needs the extra ground, but seems to be less problematic and finicky. I have no experience with any of the others. I just stuck to tried and true.
I was just doing some reading and it would seem that the stock fiero vss outputs a sine wave whereas the cruise needs to see a square wave signal. Looks like you'll have to throw together a buffer.
....with one exception: I used the VSS signal from the sensor on the trans,
You probably did a good job right up to that point . Get a yellow buffer box from a later model GM and you'll love the new cruise control. All the details about where to get the buffer box and how to hook it up have been posted many times. just use the SEARCH.
[This message has been edited by PaulJK (edited 06-30-2015).]
Most of what I find seems to be specifically targeted at the engine swap cars, and I'm having a hard time separating relevant information out of those posts, but I'll keep at it.
Despite my best efforts, I can't find a single thread dealing with what vehicles have the buffer I would need, or the wiring information for one...Any help would be GREATLY appreciated
Quote from Darth fiero "1985-89 Firebird / Trans Am / GTA. I also think you might find one in the same year range Grand Ams, Cutlass Calais, etc and other similar body style FWD GM cars; but the Firebird will be your best bet. In the Firebird, it can be found piggy-backing the ECM which is located on the right side of the dash above where the passenger's feet would be. CAMARO DOES NOT USE THIS BOX. 1982-89 Camaros used cable-drive speedos and there was an OPTICAL VSS sensor mounted on the back of the speedometer in these cars. 1990-up Firebirds AND Camaros had the VSS signal processed by the ECM directly."
Do a search for fiero buffer in Google under images tab.
Despite my best efforts, I can't find a single thread dealing with what vehicles have the buffer I would need, or the wiring information for one...Any help would be GREATLY appreciated
Here's the digital cruise control thread with buffer info
that's when I gave in and used the relay method. I also tried to skip the step about cutting the wires at the pedals, that didn't work either 
........learned the hard way. 
. Get a yellow buffer box from a later model GM and you'll love the new cruise control. All the details about where to get the buffer box and how to hook it up have been posted many times. just use the SEARCH.
