This is a strange problem and I'm having trouble figuring out what could be causing it. I have a 1992 Firebird GTA that I've swapped an LS1 into. Not sure if it matters but I did not do the conversion wiring harness myself, I had it done by Hawks Motorsports so I do trust their work, but it may not even be a wiring issue. I don't know.

When it's cold outside my speedometer doesn't work for a while but after about maybe 10 min or so of driving it starts working again. I don't have this problem in the summer or spring when it warms up. But if it's cold enough for a jacket outside this happens. Where do I start with troubleshooting this? It seems everything is connected okay if it works when it's warm so why would the cold affect it like this?

 

Do you have a scanner to see if you have a Vss signal when cold ?

 

I feel like I should have thought about doing this first! I have a small scanner, hooked up I drove around the block and sure enough it is showing a vehicle speed on the scanner but my speedometer was dead. It's warmer today than it has been so before I got back the speedometer started working and matched the vehicle speed reported by the scanner.