Blinking temperature light

[doug_d (Cameron Park, CA)]

Howdy,

I've got a '98 Boxster that has a blinking temperature light. It used to be intermittant, but has been consistently coming on for the past few weeks. Regardless of temperature, it comes on when I start the car and stays on (blinking) until I turn the car off.

I'm familiar with the four reasons for the light previously posted on this site, but I need help with some troubleshooting ideas and details. First, can you tell me how I can determine a "slow" flash from a "normal" flash? I think it's the slow flash just based on how it feels. :)

I recently replaced the reservoir cap and the light stayed away for 11 starts across 3 days, then it came back and has been on since. I've burped the system, checked for reservoir leaks, ensured correct coolant level. I just had the thermostat replaced (in addition to the light, the temp was fluctuating from the right side of the 8 (normal) to the right side of the 0). I've wiggled the sensor connection at the reservoir tank. Other troubleshooting ideas?

The float in the reservoir? (Is there one? Can I see it? ...)

Loose connection at the instrument cluster?

Engine compartment temp sensor (Where is it? How can I test it?)

I don't yet have conclusive results on whether the thermostat replacement resolved the fluctuating coolant temp or not. The mechanic who replaced the thermostat checked the basics related to the light, but needs more time to diagnose. We agreed that I would drive it for a while to see if the temp was more normal before continuing to look for the reason for the blinking light.

Thanks, Doug

1. Engine coolant level too low -- light flashes slowly (0.5 Hz)

2. Engine compartment temperature too high -- light flashes slowly (0.5 Hz) (engine compartment blower might be faulty)

3. Engine coolant temperature too high -- light is lit; pointer on the right

4. Temperature sensor at water outlet faulty -- light flashes rapidly (1 Hz) ; pointer on the right