lugnut

iTrader: (1)

Got my new engine in 84 z factory q jet 305,factory exhaust,I replaced all the coolant sensors and knock sensor,water pump,185 thermo,new rad,new cap.also had a aftermarket temp gauge hooked up to verify,running about 180 which I guess is close to the factory one,it barely gets up to the first white mark from 100 Anyway after 5 min,the fan comes on and check engine light comes on and throws a code 15 Low coolant temp,but the engine by a infra temp gun is 200,the rad is only 150 and I can touch it,unlike the valve cover which feels like it is 200,everything is circulating
I have all new sensors,is there a diiferant part number for the ecu one in the thermostat housing,just been a real pain that I cant figure out

midias

Sounds to me like your thermostat is opening way to soon or is stuck open

Does it get up to temp if you let it idle then drop back down when you drive?

lugnut

iTrader: (1)

according to the gauge it barely reached the first white mark from 100 deg on gauge idk what that is,but I just tapped into the thermo housing for a bleeder hose incase I had a air pocket,coolant does come out but in random spurts,and its hot it onlyran for a min and the fan came on,its a new 185 thermo it stays around 190 driving but throws code 15 and starts running a little rough

lugnut

iTrader: (1)

it wont get up to temp cause the fan runs,temp gun said RAD was 120

Go Blue

I'm still learning about these cars, but a lot of the other cars that I worked on had a coolant temp sensor for the ECM/Engine and another coolant temp sensor for the gauge to get its' reading. It sounds like the 1 for your gauge may be bad. Anyone please feel free to correct me!!! I have been wrong 1 other time in my life! lol.

Galaxie500XL

iTrader: (1)

Well, since you've confirmed that the radiator doesn't actually get above 120, I'd all but guarantee the thermostat has failed open.

lugnut

iTrader: (1)

All my sensors r new,checked stat in boiling water,it opened all the way right before boiling it was a 195 I put back in it. Unplugged the green wire to sensor and it finally got to 200. Still just dont know why the ecm thinks its cool and turns the fan on. I guess I can put it on a toggle,hate to fix it like that.

Galaxie500XL

iTrader: (1)

If the air conditioner is running, the fan automatically comes on regardless of temperature..could that be the issue?

midias

Don't rig it with a toggle fix it right.

lugnut

iTrader: (1)

Ok to whoever is still following this,I have circulation in the system,Itook the wire off the fan sensor so car would heat up 200.I figures that is why the ecm turns the fan on cause of the low temp,but it still throws a code 15,so now I know its in the ecm sender Someone give me the part number for the sendor that the ecm uses,the one in the stat housing.Also my wires to that sender was bad,so used a single connector for the 12v and grounded the black wire to the engine where before both wires was going to the sendor itself,but I didn't have a 2 wire connector
Hope it all made sense,The whole problem is the ecm is not getting the correct temp reading and giving a code 15 so I think I have some wires going to wrong sensors

lugnut

iTrader: (1)

Ac is not hooked up yet

midias

I think it is 15326386

mmadden55

Sensor is bad 200 is not low coolant temp.

lugnut

iTrader: (1)

I agree

JA411