Causes for temp gauge variations on 94 civic?

[94Civicman]

I was hoping someone here might be able to steer me in the right direction. I own a 1994 Honda Civic DX 1.5. About a month ago I started getting variations in the temp gauge for the first time in 13 years of ownership. This first couple of weeks the gauge would immediately shoot up to 1/4 warm on a cold startup. Then after another couple of weeks of doing that, it would immediately show 1/2 warm on a cold startup. Now after about the 6th week, I'm getting fluctations all over the place while driving around.

I haven't changed the coolant in about 42,000 miles (About 7 years ago). Yeah I know, not good, but it is what it is.

I'm on a really tight budget and don't want to throw the kitchen sink at this, should I just start with a radiator flush and see if that makes any difference? Then if that doesn't work consider replacing the thermostat or coolant sensor? If so, in which order?

I really appreciate any advice, thanks!

 

[Avant Uprising]

If its doing it right away id rule out the thermostat. Most likely the coolant sensor. Id flush it too. Also drive it for a bit and feel ur lower hose to see if its circulating.

Sent from my LS670 using Tapatalk

 

[R3dline]

its gonna be the thermostat , 99.9 % sure, its stuck. need to replace it

 

[Avant Uprising]

its gonna be the thermostat , 99.9 % sure, its stuck. need to replace it

Hes talking about before the motor would even warm up thats why I dnt think its his t-stat

Sent from my LS670 using Tapatalk

 

[94Civicman]

Thanks I'll probably go ahead and replace the coolant sensor first. The thermostat has already been changed twice over the life of the car, and as far as I know the current sensor is the original. I read that there is a coolant temp sensor and a coolant temp switch; I assume I want to change the sensor and not the switch?

 

[JohnS.]

I'm thinking thermostat as well. It's a pretty easy fix and the part is relatively cheap.

My gauge did the same thing except it didn't go as high. Some days it would go up like normal, other days it wouldn't go up at all, other days it would go up and down. I changed my thermostat and it fixed the problem.

 

[94Civicman]

**CONCLUSION:**

It was the coolant sensor. I had a new one put in and it fixed the problem.

Case closed.

 

[Avant Uprising]

**CONCLUSION:**

It was the coolant sensor. I had a new one put in and it fixed the problem.

Case closed.

Ha I knew it! Told ya

Sent from my LS670 using Tapatalk

 

[DavidR]

My temp gauge on my 99 ex is reading below operating temp, I thought the t stat was stuck open but when I took it out it worked fine, so I moved on to the sending unit. I grounded the gauge wire to the engine and the temp gauge moved up to hot then back down to the middle of the gauge so it must be good. Then I checked the sending unit sensor with a ohm meter after driving 10 miles to work and it read 60-63 ohms when the haynes manual said at op-temp it should read 30-46 ohms. So I replaced it but no change any advice would be great.