I have a 94 Prelude SI H23A1 stock. The temp gauge always reads cold and has since I have owned the car. The radiator fans still turn on periodically and seem to be working normally, idle also goes down as the car warms up. So it seems to me the ECU knows what the coolant temp is, but the gauge still always reads cold. Thermostat has been replaced and i'm thinking about doing the coolant temp sensor next, when the CTS is unplugged the car runs like crap and idles at 1500rpm so the CTS sensor must be somewhat functional. It also cranks a while to start but only when the engine is cold and it is cold outside, not sure if that's related. Any other ideas besides the CTS?

 

Temp gauge sensor

 

the temperature sender is the single pin one under the distributor

 

Oh okay that makes sense, thanks. Was wondering why I was seeing two different parts when I was looking up the CTS sensor, one is the sender. Well it's caked in oil and grease (have a leaky shaft seal) I cleaned the nipple thing and inside the connector. About to go on a drive and see if it did anything. If not i'll buy a new sender, hopefully it's the sender and not the connector.

 

Well no luck. Just ordered a new sender. Anyone happen to know if I should drain the coolant before replacing the sender? Is coolant going to pour out if I remove the sender?

 

coolant will come out when you remove the sender, but it will be a slow trickle. So no you don't need to drain the coolant. Just make sure the motor is cold, and do not remove the radiator cap. Loosen the sender until you can spin it out by hand. Hold the new sender in one hand while you spin out the old sender, then stick the new one in and thread it in, and tighten down with whatever wrench/socket. If you're quick, you'll lose very very little coolant.

 

Got the sender installed and now I have a working temp gauge. And yeah it was a slow trickle, barely lost any coolant. Thanks a lot guys, I certainly would've replaced my CT sensor if you didn't tell me about that sender.