howzit everyone
i understand and know that there are threads and write ups about this or similar but i just cant seem to get the answer im looking for....

anyways current car and problem
-99 si civic with a ctr swap

- so... ONLY when a/c is on and when im at a stop light or stopped anywhere when car has been ran for about 10-15 mins temp gauge starts to rise. i tried to see if i could get it to hit the red but it would stop at around the 3/4ish area. when im driving its fine and temp stays normal. thing is that when i first got the car i replaced the radiator/cap, hoses, main fan and obviously new coolant and bled the system correctly. ran it with no problems at all for aboout 3 weeks with a/c on blast for the ride home for that time span. once this problem started happening it led me to think it could be my thermostat so i replaced it as well and re bled the system again.. car ran fine as far as temp wise EVEN with running a/c all day before i replaced the thermostat so thats my reason why i didnt change it from the beginning.. i do understand the car does run hotter and works harder especially with the a/c on but like i said, when i first got the car and replaced everything it was running fine with NO PROBLEMS and temp was always where it needed to be. water pump is fine and head gasket is still good. besides that car runs great with a/c on or off but i see myself having to always turn my a/c off at a stop to prevent temp from going up.... so with that said, im leaning towards one of my temp sensors being bad but dont know which one to replace so i need your guys help. btw fan turns on when its supposed to so i know sensor on thermostat housing is out of the question. much help is appreciated.

thanks in advanvce!

OH and one more thing, last friday it didnt give me a problem in overheating with a/c on almost the whole way home from work. it almost did but idk for some reason it must of caught itself or something lol.

 

sounds like the fan is not dissipating enough heat off the radiator.

 

808 you posted you changed the FAN did you check to see if it was pushing AIR or pulling AIR?

 

It's wired correctly. Pulling towards motor.

 

It's weird though because it's been fine for a while.. I'm jus a little stumped on my problem.. I wanna change a sensor but don't know which one

 

Okay guys so just a little update, today was the first day actually driving my car from work to home(about 40mins away including stop and go traffic) with a/c on that my temp was good all the way home.. Only thing I did this past weekend was try to find the wire that controls the temp gauge itself and I accidently like an idiot, unplugged ect sensor(thinking it was the one that controls gauge) that's under vtec solenoid while it was running so my idle started to jump up and down.. So what I did was plug it back in, unplugged battery and ecu to reset everything, plugged everything in and started my car and idle was back to normal. I didn't reslly test it yesterday cuz I didn't run ac. I honesty don't know why it's not strangely getting hotter but I won't get my hopes up on just one day lol

 

okay so finally today is the day it started to act up again when i was grabbing something to eat in drive thru.....
once i left drive thru i turned back a/c on and drove with it home which is about a mile away from where i was then parked my car and waited with a/c on to see if it was gonna start overheating and it didnt!!!! like seriously can anybody else chime in to my problem i really need some help cuz its starting to irritate the **** outa me.... i still wanna change out a sensor but i wanna know which one would be best to change.... please lmk guys im in desperate need of some help!

thanks in advance!

 

Anybody?????

 

There's 2 temp sensors right by the distributor. The single wire probe looking one is the one for the gauge. The other one (2 wire green connector I believe) is for the ECU.

 

okay but i just wanna know which sensor i should change out of both....
i kinda dont wanna change both but if i have no other choice i will replace both...

only reason why i wanna just change one sensor is because idk which sensor could be giving me this problem... so to better explain my problem,for another example lol today i noticed when i got home(temp was already going up with not even 10 minutes into traffic with ac on only) i sat in my driveway and checked to see how long it was gonna take for temp to start getting higher and higher. it only got past half way mark and kinda just stayed there. so once it was floating at a certain spot i turned car off and started it back up real quick and turned ac on again, and temp was below normal operating temp and slowly went to normal, gave it about 15 minutes with car running and she never even moved from normal temp...

so i personally dont think it could be my ect sending unit(which controls gauge) UNLESS i am told otherwise with someone else's opinion on it.. as for the other ect sensor, i need help on figuring out what kind of symptoms and how i can for sure say it is bad.. thats why i made a thread about this is because i cant find no other info of my problem. ive been searching high and low but no good answers....

 

anybody can help?

 

I know on my 96 Accord I have two fans one comes on cause of coolant temp and the second comes of everytime I cut ac on..
The ac puts a bind on the engine which creates more heat... When a car sits still it can begin to overheat cause of the reduced airflow through the radiator..
Do you have two fans?

 

yeah i do have two fans like i posted above. and i do understand that my motor does work harder and does get hotter once ac is on but like i posted above, i NEVER had an issue what so ever on my temp getting the way it does. symptoms its giving me is as if everything i replaced didnt do no justice. i replaced all the simple things i possibly could as far as cooling besides water pump thats still good and my HG also checks out to be good too.. thats why i was leaning more towards a sensor being bad.. if u read anything i posted on how my car is acting, ur gonna see why im leaning towards that and need help figuring out my problem..

ONLY THING that i did that made my car act normal(temp wise) was i unplugged battery and ecu and plugged everything back and started car and temp wise my car was totally fine for a week then after it started giving me problems again. the way i found out what i did really worked was because i did it again JUST LAST NIGHT and today my car did just fine in stop and go traffic, no overheating at all, temp did not move from normal operating temp... so this is why i dont believe "just because my car's ac is on and not getting any airflow in traffic it would cause my car to overheat or be hotter" saying. and this is why i need help about how maybe it could be one of my sensors that needs to be replaced or something... i just dont know lol my car is seriously weird..

 

Ok so you have two fans..
Do both fans work.? I need you to check that both fans are on the next time it overheats with the ac on....
usually a sensor will throw a code...
Check the wires going into the connectors for the suspected sensors and fans for loose, broken or corroded wires.

 

yeah both fans work lol i swear i posted above.
both fans are on when it is in overheating stage.
i did everything i needed to, i triple checked my work and everything else i changed on motor. trust me i sat there for as long as i could to make sure my car was okay and 95% of the time i would get fooled because with car running and sitting in my driveway it would be fine then the next day driving home from work it would start to act up on me and i repeat ONLY when a/c is on. driving without a/c on temp runs perfect.
if u want me to re write everything i did here it is

replaced main fan(yes its wired correctly)
made sure both fans turn on
replaced radiator and cap
replaced radiator hoses
replaced thermostat
bled system good and made sure of it because i had to do this multiple times.
BOTH FANS WORK they turn on when they need to so there is no need for me to jump any switches or check any relays.
checked all wires going to sensors and traced back as much as i could to see if any wires were broken or loose and there was none.

only 2 things i didnt change because i know its good is water pump and HG. i do know symptoms of both and i have none what so ever.

believe me i sat in my driveway for long periods of time wasting gas just trying to figure out what the problem is and i havent gotten close to figuring it out yet.. only thing my car is telling me is that if i unplug battery and ecu(im assuming im resetting it) and plug both back in and run car with car already in overheating stage the temp wil be back to normal... it doesnt last more den 4-5 days tops after that happens.. so this i why at the end of the day i just wanna know if any of the sensors could be the culprit...... i need more help.

 

can anybody help???

 

Have you tried to hook up an aftermarket temp gauge? Maybe the factory gauge is wonky?

 

The single wire sensor on the left is for your gauge cluster.
Is it an OEM thermostat?

 

yes i do know that controls the gauge but in my situation im not sure what could be causing my problem because only things i didnt change is the sensors and thats where im stuck on which sensor would be more likely to be the one giving me the problem... i still havent gotten a chance to even try changing the sensors because i have no time right now.. the sensor/switch that controls my fan is still good because fan comes on.

and i think it HAD an OEM thermostat in there but i replaced it so its definitely not OEM. btw the system is flowing good and bled good as well. and now that i know the thermostat change didnt really do any justice i think my old thermostat was still good but thats okay.

 

Just because your temp gauge is fluctuating doesn't mean your actually overheating.
Check both connectors pins for corrosion and condition. The ecu resetting that seemed to make a difference is coincidental I think.

 

If your running a usdm ecu (probably not) you should be able to hook up a scan tool and view live data from the ect sensor( the one for the ecu for fuel trim).

 

actually i am running the one that came with the motor at the moment. im still working on getting a power fc because a friend of mine has no use for it already so right now i cant use a scan tool.. but yeah i am hoping gauge is jus fluctuating and im not really overheating....

btw thanks for replying back, ur the only one thats giving me fast answers lol.

 

SeeYou could probably use a usdm ECU to plug in and idle while watching your temp sensor. It'll throw a CEL for all the jdm/ USDM Differences but you should still be able to watch temp via scan tool.
You could also try using a multi meter on the sensor and watch it change as the car warms up.
How's the connections and pins look at those 2 sensors?
Loose or corroded pins mean high resistance which means inaccurate signal being sent.

And your welcome ☺

 

The ect sensor for the ECU can't cause an engine to overheat. It simply tells the ecu what the engine temp is so it can adjust fuel and ignition accordingly. You could unplug it or remove it completely and your engine temp shouldn't really change much.

The sensor for the gauge only reports to the cluster. It has no effect on engine operation.

If the connector looks good and fits snug, next I would check the wiring for opens and shorts. Unplug the cluster and find the pin that controls the temp gauge. Check reresistance from end to end and repair if needed. (Unplug the sensor and the Cluster. You want to check the wiring seperate).

 

squirt a little water on the coolant sensor that controls your gauge in car and see how it reacts. You can also you use a digital thermometer to check around that area for overheating maybe from a restriction through holes from head to block..