May 29, 2013 at 8:29 pm #6501
EDIT: I may have solved the problem. I think the auto parts store sold me the WRONG SENSOR. It was labeled “coolant temperature SWITCH” in their computer, so we assumed that was the correct one. But if I unplug the OTHER sensor, the fan operates. So I’m going to try replacing it instead.
I have a 1994 Quest that runs fine otherwise, but for some reason the radiator fan will not operate.
I have followed the entire flowchart from the factory service manual except for the part that requires the Nissan diagnostic computer. Everything checks out… except for fan operation.
Here is what I’ve tested:
1. Check Low Speed Operation (engine warmed up) -> Fan FAILS to operate. (FAIL)
2. Power supply test – battery voltage present at relay terminals 2 and 3. (PASS)
3. Ground Circuit Test – continuity exists between fan harness & relay terminal 5, continuity exists between fan harness terminal c and body ground. (PASS)
4. Check ECM Output Circuit. Check continuity between ECM Terminal 9 and Relay terminal 1 (PASS)
5. Check Cooling Fan Relay Operation – Relay shows continuity when voltage applied to proper terminals (PASS)
6. Check Fan Motor – Low & High speed operation both pass when connected to battery voltage using test leads. (PASS)
On my own, I also checked the fusible links, though if they were blown it should have failed continuity which it doesn’t.
The one thing it did NOT specify a testing procedure for is the Engine coolant temp sensor. However, to cover my bases, I replaced the sensor. Also, it says that if this item has failed it should set a check engine light. The engine light is NOT illuminated (though it does illuminate momentarily at key-on so I know the bulb is fine)..
So… the fan motor has been checked, the wiring appears fine, the relays appear fine, the temp sensor is new, etc etc…
What could be preventing the fan from operating?
- This topic was modified 4 years ago by aelfwyne.
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