strange overheating issue

[tdi-tom]

Hey guys I've done some searching around and came up with nothing, just recently my 92 gs has started getting uncomfortably high on the temp reading. This ONLY happens when the heater is on, doesn't matter if I'm parked or cruising down the highway and only happens shortly after the heaters turned on? It's happened a few times and I didnt notice until I was basically in the red zone but as soon as I turn the heater off the car cools down to normal operating temps. Any ideas?? Does not matter if the car Is warmed up or cold either, I live where It gets pretty chilly and I see this being a big inconvienience!
Thanks in advance!

[mitmaks]

Did you check your coolant, level/quality. Perhaps flush and refill would fix this + new thermostat

[Thefez]

New rad caps too. That solved my over heating issuses

[mitmaks]

When was the last time you did timing belt/water pump. If water pump is old it might be leaking coolant or vanes are worn-not circulating coolant properly.

[tdi-tom]

I recently had an oil change done (had no time!) and they say the quality and watnot is good and I can see the level Is bang on, timing belt and waterpump was done aswell not too long ago, So they should be all good. I dont understand why it would only heat up so hot only when the heaters on, we just did a 1000k trip a week ago and this was never a problem even with the heater on or not. I could try a new cap on payday.

[mitmaks]

Perhaps you have restriction somewhere in heater core and it restricts flow and starts overheating

[tdi-tom]

At this point thats all I can possibly think of, how would I go about freeing a clogged system up? Still makes me wonder tho because coolant is always flowing right? I don't have this problem any time other than when the heaters turned on. Still runs like a top when heaters off.

[mitmaks]

Maybe it's simple fix like a bad coolant temp sensor