Fans on constantly... with NO delay relay

[Grand_87_national]

Hello all. I have a problem that has presented itself before ... but promptly went away before I could troubleshoot. Now it's back. I have intrepid fans with a nearly new caspers harness and relays, installed by previous owner shortly before I took possession 6 months ago. The fans, at some point during the time it sat dormant for 2 days, decided they needed to turn on and drain my battery. Fan delay relay was removed prior to my ownership. First thing I did, was remove the caspers relay to test it, and it is functioning as it should. Next, I charged the battery, started the car, and quickly checked the coolant temp on the scanmaster. 70* and coming up as it should. So, I'm lost. The scanmaster tells me that the sending unit is giving the ecm the correct signal, yet the fans are energized. I've owned the car for 6 months and it's only done this twice... the first time (3 months ago?) it took care of itself after installing a new optima battery and the fans have worked perfectly since. I'm almost to the point of installing a kill switch in the ash tray enclosure that will kill the power to the relay, but I hate to do that. Is my ecm bad? What could cause this? Thanks in advance!

 

[Frederickdav]

It sounds to me like you need to check all the "new" relays and switches. Just because something is new doesn't mean it's good. Just a thought. Good luck.

 

[Grand_87_national]

It sounds to me like you need to check all the "new" relays and switches. Just because something is new doesn't mean it's good. Just a thought. Good luck.

Indeed. And already done. 2 relays with the harness (one with 3 blue wires and a black then another with 3 red wires and a black) tested both relays and both good. Also tested relay plugs and found the trigger (85) to be hot on the red side even though the car is room temp. It's definitely getting energized and the relays are functioning properly. Also, the ecm (per scanmaster readings) is seeing correct signal from the sending unit.

 

[RmvBfrFlght]

Does this setup use the two stock high/low relays? If so the coil power is ignition switched. With the key-off there is no power to those relay coils, so they shouldn't be activated. I mention this as the fan(s) turned on and drained the battery.

It is possible that one of those two relays are bad.

As for the fan(s) running with the engine running, the ECM only controls the low speed relay. The high speed relay is mainly controlled by the temperature switch in the top/front of the intake manifold. Can simply unplug it to see if the switch is shorted.

Also, both low & high speed relays have a switch on the A/C pressure line. That switch could also be having issues, or possibly you were running the A/C. Again, simply unplug the connector for this switch to see if it is causing the issue.

RemoveBeforeFlight

 

[Grand_87_national]

Does this setup use the two stock high/low relays? If so the coil power is ignition switched. With the key-off there is no power to those relay coils, so they shouldn't be activated. I mention this as the fan(s) turned on and drained the battery.

It is possible that one of those two relays are bad.

As for the fan(s) running with the engine running, the ECM only controls the low speed relay. The high speed relay is mainly controlled by the temperature switch in the top/front of the intake manifold. Can simply unplug it to see if the switch is shorted.

Also, both low & high speed relays have a switch on the A/C pressure line. That switch could also be having issues, or possibly you were running the A/C. Again, simply unplug the connector for this switch to see if it is causing the issue.

RemoveBeforeFlight

You are the man! I had actually jumped on here to update the thread, since I found the culprit early this morning. You see, I was told this was a stand alone harness and took the factory relays out of the equation... not the case (as you already knew) the harness appears to "carry the load" of the fans, however, the trigger for these new relays does come from the factory hi/low relays. Previous owner apparently wasn't aware of this even though he said he installed the fans and new harness. ??? Oh, well. As soon as I descovered this, I knew it had to be the issue. Tested them, and one is toast! I have 2 on order at autozone, and I'll replace them both tonight. Thanks a bunch for the help!