couldnt find the right forum, please assist
most cars run at about 210 or so, mine runs around 180 when its below freezing here
but i wish i could help you further, my fathers car is having the same problem, it will only heat up to around 170, then dip back down to 140 or so.. he even gets SES lights because the engine didnt reach a normal operating temp after so many minutes
Blazers are well known to have heat issues from a plugged heater core.
The fix is to try & flush it out. Carefully remove the heater hoses from the core. use a piece of heater hose & a garden hose to back flush the core. Put water thru the core each way & flush till it comes clear. Very rarely do they clog past the point of no flushing, but does happen, mostly fords.
Then reinstall all the piece & bleed the cooling system & recheck it.



