2002 Chev. Traiblazer- heat guage jumps from low value to high values almost instantaneously . The dealer has replaced the water pump and the clutch fan but the problem persists. Sometimes there is no problem, sometimes the guage reads low. The radiator does not seem to be overhesting but when on a trip this heat guage jumps around.

ur problem cud be a tuneup--change or test plug wires--coil--etc/alsoinjectors may need cleanin or u may have vacuum leaks--do a complete inspec and a data stream run to get values-code readers arnt enuff info---------obtain a repair manual for procedures and dont go to a dealer

I would suggest having the engine temperature sensor and circuit checked, as well as your engine temperature guage. The guage is best checked with the use of a scan tool used by the dealer or a repair facility. If no signs of actual malfunction of the vehicle are present, you may just be throwing money at the car because of a false reading on your temperature guage. Some cooling systems require a specific filling procedure. If not done properly, air will be trapped in the system, causing similar issues to what you are experiencing. That would also cause loss of heat in the cabin, as well as overheating of the engine.

"Most Fords have a CCRM (Continuous Control Relay Module) thats on the passenger side fenderwell. It has 4 relays: one for the AC compressor cluth, one for the fuel pump, and two for the electric fan (high- and low-speed.) The AC is the one that fails the most. You can replace the CCRM by removing the intake air filter box and working through the fenderwell openings. If it gets to difficult you must remove the wheel and splash cover to replace it from the wheel opening." - H-andy Mann

with the engine idling, tap on the ccrm and listen for the clutch to come on. if it comes on, you need to replace the entire ccrm.

Take the compressor relay out and give power from there.

Low retail valve $1950.00
Average clean and in good condition $3100.00
High retail valve $4375.00
Hope this was very helpful

get a welder and re-weld it ,not a big issue ,all dealers say this so they dont get dirty dirt work because it might make their garagefloors dirty ,also main dealers do not have proper mechanics that can do this sort of work they only employ young unit changers that work for peanuts,and you know the saying if you only pay peanuts you only get monkeys .I mean in all honesty do 6 years training ,come home with diesel oil grimed into hands when if you do four years training you can become an ambulance chaseing solicitor and earn a lot more without getting hands dirty and being a social outcast because of it .

check for coolant leak in system, if ok, replace thermostat. make sure water pump is working properly.

low freon soumds to me.. jump out the low pressure cut out switch near the dryer...or jump clutch relay in the distribution center. with clutch ingauged hook up guages to check low and high side pressures... also easy trick go to auto store get a can of 134a freon with hose and add the can the clutch should stay inguaged longer and longer as you fill the sytem... with clutch inguaged rev motor up to 1500 the guage on the hose should be around 35 to 40 pounds if low add more

Is that your static pressure readings??? If that is your static pressure readings that's good. When the engine running and fan on high and a/c compressor clutch engaged you should have 25 to 35psi on your low side and 200 to 350psi on your high side. If the clutch is engaged and that is your readings, replace your a/c compressor. Keep me posted, be glad to help.

is it ever low in coolant? i agree with emissionwiz sounds like your getting airpockets do you have heat when this starts?