I have a 1998 ssei I am restoring Just put in new motor & did a full clean and flush of the cooling system. It ran fine every thing worked fine including heat. Had to replace AC Compressor so it sat for about 1 week. Now when I first start the car air blows warm then the temp indicator flashes and it switches to luke warm air. This happens in auto or manual. If I shut the car off wait a few then start again its warm again. The diverter is switching from floor to vent fine so not sure what else to check. Please help

Please explain where the temperature settings on your climate control are when this is happening. If you are asking for heat and it fluctuates between hot and luke warm, you probably have an air bubble in your coolant system. If you are asking for cold and it flucuates between hot and luke warm, there may be something wrong with the AC compressor or its connections.

On top of the T-Stat housing is a small bleeder valve. Open that slowly until coolants leaks out. Start the engine and wait for the temperature to get up to operating levels. Open the bleeder valve again...be careful there will be pressure and heat there. Do this a couple of times, waiting about 5 minutes in between each bleed.

Let the motor cool down, hit the bleeder one more time. Top off the coolant and see if the heater problem hasn't gone away.

Tried bleeding it did not help. It does not seem to matter if I am trying to get hot or cold air it still flasshes. But when it first comes on and the engine is warm i get hot air. I did take a long drive and it started working but it quit again when I shut the car off. If I turn the car off and start it back up several time sometimes it will work. I think it mey be the actual controll pannel in the dash but not sure does this information help anyone narrow it down for me?

I'm a complete noob and this may not apply to your situation but I read here on these forums that air can be trapped in the Heater Core, The suggestion was rev the car at bout 3500 rpm for 10 seconds repeating this about three times, then bleed at valve at the T-stat, worked for me finally got heat. good luck with your problem.