Mailbox Hunter

I just finished an engine swap on my car from a 305 to a crate 350. I got all new sensors and refinished the radiator, as well as replaced the fan motor.

Now the fan WILL turn on if i turn on the AC, so I know the wires to the fan should all be fine. But under normal operating, the engine will continue to heat up, and the fan fails to start. I have a 190 degree thermostat in the block currently.

Also it is important to note I STILL HAVE the 305 computer and injectors on the 350 block (temporary, but note it) also while plugging everything back in I had the knock sensor and passenger side temp sensor wires switched (idk if it had enough power to kill the sensor). All my fuses check out fine, I have a check engine light on, I have yet to diagnos and check the code.

That's it, any questions please ask. Please. Any ideas, no matter how small, are appreciated. I don't want to turn the ac fan, or run a switch, to activate my fan either. (have considered.)

Mailbox Hunter

Also the lower black plastic air dam cover from the front bumper to the lower scrape fin isn't on. But the car is being run on jack stands, so it shouldn't matter,

deadbird

Stock TBI fan switch turn on temp, 238°F (+/- a few degrees).
Key on, ground fan switch wire.
Fan?
Yes, switch didn't hit grounding temp or, possible bad (poor manufacturing).
No, circuit issue.

hwcoll95

iTrader: (6)

i'd say fan switch ,and like was said come on at a real high temp anyway

Mailbox Hunter

Nope. The fan control sensor worked fine, the gauge temp sensor is off by 20 degrees soothe gauge says the engine is 250-260 when really it's 230-240. I checked with a laser thermometer.

Also the plastic housing on the relay melted (somehow) into the socket controlling the switch to the fan (green and white wire). Took some time to diagnose, but thats what it was. Now I have this new issue...

Riddle me that. Why does my gauge show the temp is 20 degrees hotter?!

deadbird

gauges can get a certain amount of inaccuracy after 19-29 years, they aren't Swiss made. though, the sending unit can go bad as well as the wiring so, it is not always just a 'crappy gauge' causing the problem.

Mailbox Hunter

The gauge worked fine up till the swap. I did replace that sensor also (sadly, the old one was discarded). Any way to remedy the situation? Im fine knowing the gauge is off, but (god forbid) I go to sell the car, the buyer might not be. I know I'm not happy with it.

ternandes

iTrader: (7)

You can't expect the gauge to be '*****-on' accurate. No buyer in his right mind will either. You could try replacing the gauge sender again...

Here is an excerpt from a tech article:

The fan is controlled mechanically through an in-cylinder head thermal switch and through the
mechanical A/C slider switch. The in-cylinder head thermal switch is designed to turn on the fan when coolant temperatures reach 222°F (or higher) or when the A/C is turned on. There is no ECM control for the fan on single fan applications.

Check your wiring to the relay from the thermal switch. If it is OK, and your switch doesn't turn the fan on at the prescribed temperature, then the switch is bad. The only other thing I can think of is an abnormally low coolant level. If the switch is not in contact with the coolant, it will not read right.

Mailbox Hunter

Well I know all the wires to and from the relay are fine (pain staking to check), I think I'm going to try another sensor and/ or reseat my current one. The fan DOES kick on at 238 like it should, and my coolant temp reads the same (again checked with a laser thermometer).

Aftermarket gauge? I really think a temp sensor is something I really need.