I installed an Avital remote start in my 1999 Camaro. Everything works like it should most of the time. When it is a really hot day the remote start does not work. The car goes threw the motions of wanting to start but nothing happens and if you let it try three times or so the security light stays on and you can not start it even with the key for about 5 minutes. So I was wondering does heat effect a resistors value. I did not have to buy a bypass module for this car. I just used a relay and put resistors to together to match the resistance of the resistor in the key. I installed this last winter and cold is not a problem and on the really hot days when it does not work just drive around for 15 minutes with the air on and it will work fine
The resistor should not change value with normal heating up of your vehicle. It may help to eliminate this from the equation if you could check the resistance with the car cold, then check it with the car hot. I do not think you will see any difference, but it will be the only way to eliminate or verify that this is the problem.
I'm not really sure about heat making a big difference to a resistor.
Resistors, after all, are a regular part of many electronic devices.....and many of those devices heat up when in normal operation. Think about all of the things you have around your house......phone chargers, laptop computers, any type of audio equipment that has an amplifier.....most of those things have resistors inside, and get very warm during use.
I wonder if it's either the vibration of you driving the car around, or another possibility is that metals contract and expand based on temperature. You could have an iffy connection that when the metals expand, the connection "tightens" and works, and when the metal contracts, the connection gets "loose" and therefore doesn't work. Just a thought; I don't really know.
Anyway, the VATS supposedly has a 5% tolerance.
Here's an article showing the acceptable resistor ranges:
https://www.joestradingpost.com/vats/89_passkey.htm
https://www.joestradingpost.com/vats/89_passkey.htm
Maybe you're right on the edge of the acceptable resistor value?
If you really want to be in-and-out and fix the car in one shot instead of going back into the dash over and over again........intermittent problems are usually the hardest to figure out and fix.
In this case, I would "trust nothing" and make the assumption that any part of your VATS bypass could be to blame. Easier to re-do it all in one shot instead of taking the car apart dozens of times.
I'd get a new resistor, go back in there and re-do EVERY connection that goes between the remote starter, the relay, the resistor, and the car.
It's rare that a relay fails, but if you have extra relays around, I'd swap that out too.