A couple races ago my shift did not activate until the rev limit at 7400. The rpm activation switch had a 6600 chip. The next race i replaced it with a known good 7000 chip and seemed fine. Next race into the 4th round it did the same after shifting fine until then. 5th round lost due to the problem. 6Al box being used with powerglide and co2 shift, dedenbear air shift and chetta Turbo Action shifter. Is it the 6al, activation switch or another bad chip? Is there a way to check these. I did check the chip and the ohms are correct. Ideas?
Thanks

Check the wiring and Grounds on your shifter and all components related to it.
With many electrical components they work or they do not at all. If you have an intermittent problem it usually comes down to bad ground or wire.

what kind of shifter activation are you using? Are you using Co2 or a shiftnoid?
Anytime i have a "funny" electrical issue, I go stright to a "voltage drop test" this is a little harder with a rpm switch, your going to need a ignition tester to activate the switch.

Joe

C02, you mean test the switch or shift solenoid by hot and or ground? ignition tester?? not sure i know what you are referring to. Thanks

What is the “rpm activation switch” device (Brand / Model ??) that has the chip plugged into it ??

Try checking the RPM plug-in ports for tight fitting connections. By this I mean the Female pins in the 6al that are spring loaded to accept the male pins from the activation switch and/ or chip. If the male pins don’t fit tight try closing down the female pins with a small screwdriver.

I've had a bad ground effect my shifter with an electric solenoid. I hoestly can't remember if it was the ground on the RPM switch or the solenoid itself. I had some grounds stacked and even though they were directly to a battery ground it gave a problem. I changed it over to a terminal block so each ground has a separate terminal and one heavy ground cable to the block.

Check the resistance of the chips. They can vary quite a bit and cause your issue. If a chip is failing, or if there is an issue with the module, you'll run into your issue. If it were me, I'd pull the chips altogether and plug in a controller. They make them for that and all you need to do is turn a dial. They are more accurate than the chips and more repeatable.

Those MSD RPM chips are just resisters. It’s about the last issue in issues like this. Look close at the socket like holes the chip plug in. It’s a mechanical connection and may be loose.

Check your shifter and air solenoid

I had a problem like you described, it was the shifter itself. They need to be lubed every 20 years or so. Who knew?

Or it's an electrical gremlin. Like others have said, look at the grounds.

Gl