The on-going saga of the rad fans not running - the updated situation

Hey all…I’ve posted about this before, kinda convoluted…so here’s where I’m at, including all the stuff I’ve checked. I’m at the point where I’m going to figure this out myself if it kills me/drains my bank account (ok ok…too far :).

I’ll include the background for those who aren’t familiar with my automotive woes.

Vehicle is a 2001 Grand Caravan, 3.3L V6, 100k miles.

Van was running a bit hot the one day (usually stays right at a notch below half way on the gauge), not overheating but hotter than usual and I was in the city but not bad traffic. Popped the hood and saw that the fans weren’t running. Tried turning on the AC, no change.

Once I was driving at a constant speed, the temp went back down to where it normally always sits, and since then is always good when you are on the highway or constantly moving one way or another. Soon as you are sitting idling or in stop and go, it starts to climb.

Checked the fuse, looked good, tested it, no problem, and tried a known good one to make sure. Fuse is fine.

Ran 12v direct power to each fan motor and they run without a fuss.

I put my laptop on the OBD port and monitored the actual temp, and while idling watched it climb to 220 F and at around 223-225 F the fans finally started running and cooled down the engine to 207 F…but then it started getting hot again, and the temp gauge in the van still shows hotter than usual.

Today, I replaced the rad fan relay (the big sucker with the heat sink) with the dealer replacement part. No change. Fans still run after the temp goes really high, but they don’t kick in earlier to keep it down to where it used to be.

I assume that the wiring is fine since the fans DO run eventually.

What else could it be? What else can I check? This is driving me nuts.

Thanks in advance…


Coolant temp sensor? That’s the first thing I’d replace.

If the fans don’t run when you turn on the AC, there is a problem. The fans work, but the sensors, relay, etc, telling them WHEN to work is where you need to look.

There is a coolant temp sensor for the engine, and there may be another one for the radiator. Replace them, and see what happens.

I thought about the CTS, but my Haynes manual says that there is only one for this van and that if the gauge is showing hot, the ECM should be getting the same data…does that sound right?

The sensor is pretty cheap so I might do it anyway…could the thermostat do this too, or would it just run a bit hot on the highway/during constant driving still?

Does your car have two fans, or two fan relays/circuits? (e.g. labeled something like FAN LOW and FAN HI, or FAN #1 and FAN #2 in the engine wiring box?) It sounds like maybe the low-speed circuit is bad but the hi-speed is working fine. (the Haynes manual would show this in the wiring diagram at the back of the book)

It does have two fans, but only one relay, one fuse. Power is applied on/off quickly to control the speed of the fans on this vehicle. I’ll check the back of the Haynes manual for any circuits…I figured this would be all controlled by the ECM.

WHAT are you expecting the cooling system to do? It’s turning on the radiator fans and cooling the engine when the coolant temperature gets to a nominal value. The engine isn’t overheating; so, what’s the problem?
The only thing not right is the radiator fan(s) not coming on when the A/C is switched on. Find out what (from the wiring diagram) circuit the PCM depends on for turning on the cooling fans. It may be the A/C switch, itself; or it may be an A/C refrigerant line pressure switch. The wiring diagram will show which.

Then why the change? Why would it suddenly start running hotter than it used to? Even when the fans run, they are not cooling the engine back down to where it used to. Something has changed, this is not how it’s supposed to (and previously did) operate.

I’ll check the circuit diagrams and see if I can find anything helpful there.


Well folks, color me silly. Should’ve checked the simple, cheap stuff first.

I found out from a Chrysler tech that the fans should come on at 220 (low speed), and then 230 (high speed), so it seems like the fans were actually running at the right temps all along. So I thought maybe the thermostat wasn’t functioning properly, after seeing on my laptop that the coolant temp goes pretty high before the needle on the dash gauge actually moves…I considered that maybe it was running hot all the time but I just didn’t see it on the temp gauge.

After replacing the thermostat and “burping” the system, and adding the right amount of coolant/water (the rad was full but I noticed the overflow tank was a bit low), problem is solved. The old thermostat doesn’t seem to have been opening completely or at the right temps.

Now, if I start the van and let it idle, the fans actually come on at 160 F at low speed, and the engine slowly warms up to 185 before they turn off. Then it continues to about 195-200 and at that point, it appears that the thermostat opens, because the temp starts to head back down to 185 all on its own, without any help from the fans. It’ll continue this cycle if I just leave it idling.

Why the fans are running at 160 now is a mystery to me, I wonder if there was low coolant before and there wasn’t enough pressure? In any case, it’s all running like it used to now, after a few test drives. Turning on the AC still doesn’t run the fans, but I suspect that’s just a wiring problem…not a huge deal.

Thanks for all the input and suggestions, wanted to let you know the conclusion…it’s too bad I replaced the rad fan relay unnecessarily, but I guess I won’t have to worry about that failing for (hopefully) the life of the van…and if it does, I have a backup now!

NOW, it ain’t right! You fix’d it real good! Actually, methinks that the dash temperature gauge be remiss. Use an infra-red thermometer on the radiator. if’n you don’t have one, a repair shop might do a “courtesy” temperature check for you.

Why? 195 is what the thermostat is rated for…it’s operating normally now. The temp reading I’m getting is via the OBDII port…and the dash gauge also stays at the right spot now.