Greetings,

I have a 1999 grand voyager with 174,000 miles. I have had issues with the cooling fan motor relay as many of you may have experienced yourselves. I didn't want to keep dealing with replacing fried relays so today I bypassed the relay and hard wired the fans.

I ran wire from the battery positive terminal through the firewall to a toggle switch on the steering column shroud, then back through the firewall to a 30 amp inline fuse. After the fuse, the wire splits and goes to the positive wire for each fan. Ground comes from the battery and goes to each fan.

Fans work great now. I flip the switch and they both come on. The bad news is that now the van won't start. When I turn the key, I hear a slight knocking sound (starter solenoid?) But nothing else. The motor does not try to turn over.

I'm guessing that this is a fail-safe to keep the engine from running if no cooling fan is detected by the computer.

Any suggestions? I'd really like to avoid undoing my day's work and returning to bondage under the cooling fan motor relay.

Thanks.
Ryan

 

30amp seems like kind of a lot of juice to be running thru a switch in the dash, just my 2c.

As far as the fail-safe concern, I'll have to research that for you.

 

what engine does it have?

 

3.3 liter v6.

 

Description of how the cooling fan system works:



edit:
Ugh, stand by, the pic is too small to read

edit2: fixt

 

Thanks for the information, issakar. I'm not sure how to put that info to use though. What do you think would happen if I jumper the contacts in the old plug?

 

If you're referring to the radiator fan relay I wouldn't go jumping any connectors. That's a good way to burn up your PCM (engine computer) since there is a wire that runs from the connector to the PCM.

The radiator fan relay is a 4 wire connector that has a single wire that comes from it to a splice, that feeds both fans.

I haven't seen anything that says disconnecting the radiator fans (you've isolated the fans it sounds like which means as far as the PCM is concerned they are disconnected) would cause the vehicle to experience a no start condition. I am seeing note of a DTC being set if it detects an issue w/ the fans.

 

First, the fuse should always go before the switch. If there's a short in the wire from the battery to the switch in your present setup, you could start a fire.

Second, the most common cause of multiple fan relay failures is improper installation. The relay uses the frame rail as a heat sink to cool the solid state electronics. You MUST clean off all rust from the frame, apply dielectric grease to prevent future corrosion and then attach the relay. And you must clean the ground wire connection G100 on the left frame rail and coat that with dielectric. If you don't follow those instructions, the new rely will burn up fast.

Did you disconnect the power feed to your new setup to see if the van starts with it disabled?

I've gone over the diagrams and can see how the PCM could even tell that you've messed with the wiring. The only connection between the PCM and the relay is one wire that provides a pulsed output to the relay to tell it how fast to run the fans.

 

That matches up with what I have seen in the diagrams too. The only connection I see w/ the fans and the PCM is like you said to provide a control circuit.

 

Thanks for everyone's input. I was able to get everything working this afternoon. I pulled my ground wire from the negative terminal of the battery and grounded my circuit to the frame and that fixed it. Now the fans run off the switch I installed and the van starts and runs as normal.

Do you think it would be worth my time to add an inline fuse between the battery and switch? As a previous reply had pointed out, that's where the fuse should have gone.

Thanks again for your time. Have a nice day.
Ryan