Car works just fine, have heat etc. My mechanic had a quick look and said that the sending unit and thermostat is fine. He will spend more time on it soon. But, I was wondering, is it possible that the gauge itself is broken! If so, can the temperature gauge be replaced or would I need a complete instrument cluster? How much would that cost? I will probably look at junkyards first.

 

Tell us a bit more about the problem. is it intermittent, did it just happen one day, are there any certain conditions that cause it, how long has it been this way, etc.

it IS possible that the gauge itself is broken: my speedometer will die intermittently in cold weather but cruise still works. In your case though, it could also be wiring somewhere along the way from the sending unit to the gauge cluster

you'd probably need a new instrument cluster since everything is in one package and if you take it apart you risk over or under-tightening screws and having more gauges (like my speedo) not work.
At crazy ray's junk yards here in the baltimore area, instrument clusters go for $25.47 and there's usually 1 or 2 1st-gen RLs. New is $175 at acuraOEMparts.com.

 

oops, saw the wrong part (cluster panel trim). actual gauge cluster new is prohibitively expensive.

on a side note, why can't we edit posts?

 

It just happened on day. Has been about 2 weeks or so. Temperature needle is at the lowest most possible position. Hmm, sounds expensive!

 

maybe an air pocket in your cooling system? try bleeding to make sure.

You can just replace just the coolant gauge, but you will have to buy a whole used cluster to make it happen. Also there have been revisions in the clusters several times, so earlier years will look different. They will have different fonts and light positions. Not to meantion really early ones didnt have vsa.

I believe that in the 02 RL the sending unit sends signal straight to the gauge. in the 03-04 the sending unit sends a signal to the ecu and then the ecu sends a signal to the gauge.

 

You might find a gauge cluster on ebaymotors.com. Be careful as they are different year to year and for the base vs. premium. I sold the one from my old RL for $75...