Temp gauge fluctuates with air vent flow?

Hi everybody! I have a 2001 Honda CR-V SE, and I’m having a little trouble with it =(

About a week ago I noticed that as I was driving around the city, my temp gauge was going up and down. I had the heat on, and when I was pressing the gas, the gauge would go down. When I coasted, the gauge would go back up to the middle. The gauge never went higher than the halfway point.

I thought it was possible that my fluids were low, so I checked the coolant reservoir. It was empty, so I added some. The radiator itself was full to the lip (like the manual says it should be, if I interpreted it correctly). The first day or two, didn’t notice anything, but then the gauge seemed to start falling again.

Anywho, I decided to drive back to the big city to get it fixed, a 3 hr drive, last night. The car seemed to be operating fine. I did not have the heat on, but there was air flowing through the vents. The gauge started to creep downward, so I thought “Hey, let me hit that button that closes the vents” I did that, and the gauge creeped back up! Problem solved right? Negative! It was raining, so when that button was on too long, my windows got foggy. So that’s how I spent the next two hours, button on, button off, then I finally just opened the windows to allow the air to circulate. In the meantime, I stopped for gas, allowed the car to idle for a while (no air/heat blowing at all) and the guage didn’t move. It stayed in the middle.

Closer to the end of my trip the gauge started to creep upward, over the midpoint (The first time it’s done that since this whole thing has started). Once off the highway, I turned the heat on that first notch, and the gauge went back down to normal.

At any rate, so it’s Wednesday. I’m planning on getting the car to a shop on Friday, but in the meantime, I just wanted to get some info out there from the community. I’m pretty nervous about whats going to happen. I just had my car at an oil change place 5 days ago, and the guy didn’t put the oil cap back on the engine, so I literally was driving for 3 days with oil spewing onto my hood (Checked the levels by the way and they were fine). The only way I would’ve known is that I opened the hood to check the coolant levels. I noticed the gauge issue last Wed, took it in for the oil change Friday (In which they said all my fluids were fine), checked the coolant Monday, and drove it 3hrs last night.

Are there any specific keywords I should mention to the mechanic for him/her to check? Is there any specific type of place I should go, or is this something any mechanic shop can fix?

Thanks for any ideas!

Sounds like your Radiator may be headed for the scrap heap. The issue you are describing leans heavily toward the inability of your radiator to shed heat… Radiators DO actually go bad…especially when people use “HArd” water in their Coolant…the minerals in the water clog the passageways in the Rad… and then the rad cant shed the heat it needs to.

WHen you rev the engine the temp drops bec the water pump is circulating the coolant more forcefully…When you turn the heat on …Your “Heater Core” is then aiding the Rad in shedding heat… The heater Core is actually a miniature little Radiator in your cabin that provides you with heat…same as the one under your hood.

I would flush the cooling system using a Rad flush chemical (Cheap to do)…then Install a new thermostat (ALso inexpensive) and then see what you get… Both of these items you can probably do yourself… If its fixed…Great…
If NO change, then you need a new Radiator… Thats about it methinks

Go to Autozone.com and look up your vehicle repair manual online…its free…the procedures are detailed in there for you.

This car is old enough to need a new thermostat.
It’s cheap and I like to change it every 4-5 years on a car that’s driven daily.
Get a replacement from Honda, not aftermarket, they’re better made IMHO.