Intermittant alt & brake lights when warm

After getting warmed up, my alternator and brake warning lights come on and flash off intermittantly. They seem to stay off for longer periods when I'm idling. Even when they are not flashing on/off, I can see from the headlight output that there is intermittant dropping of electrical. Also, my speed control stops working when the warning lights start coming on.

Replaced the alternator recently when the reverse happened - the lights came on when cold and went off when warmed up.

When I had the system checked (after alt replacement) for this recent (warmed) issue, the guy said there was too much "noise" in the system for him to read the alternator output.

This is a 1990 Camry V6.

Thoughts fellas??

=================================== Advice would have been to keep the high quality Denso alternator and just replace the brushes for around $20. Let me guess - you replaced the alternator with a rebuilt unit? If so, you probably got a worse alternator than the one you traded in. Just generalizing based on similar past experiences. Current advice would be to get a genuine Toyota remanufactured alternator and that should solve your problem. With "rebuilt" alternators only the defective part is replaced. With "remanufactured" all parts subject to wear are replaced. After going through five generators, three starters and three water pumps on prior vehicles, I now purchase only Toyota remanufactured parts and never have had another problem since. I have found better prices online from authorized dealers. Occasionally the local dealer will price match on larger orders and save the waiting time. Usually over $100 there are no shipping charges. =========== Does sound like your mechanic is not too knowledgeable though, a simple voltmeter on the battery terminals with the engine running will show you the alternator output.