Greetings. It's been a while. You guys were awesome with my last problem.

The other day the van started overheating. The fans had been very loud (sounded like a turbine) so I figured those would be the problem. I watched a vid on YouTube and replaced the fan assembly. The vid also showed how to check the relay, so I checked that and found that it was bad so I replaced that as well. Oh, while I was there I replaced the thermostat since the heater took forever to blow warm air last winter, but I digress. I topped the fluid as thought I was done.

<cue the dramatic music>

The fans wouldn't come on and the van overheated again.

A buddy suggested the temperature sending unit thingie. It didn't sound like that would be the problem since the gauge worked on the dashboard just fine. I looked online at NAPA and saw that it was only $17, so I went for it.

I brought the old one with me. The guy at NAPA brought what he thought was the new one and it had a different plug. He looked again and brought the right one and then explained that the van took two and that one was for the gauge (the one I removed) and the other was for the computer.

I cannot find where it would go.

<increase volume of dramatic music>

So, looking at the ol' handy Haynes manual, I'm even more confused. Illustration 3.13c (pg 3-3) shows an Engine Temperature Sensor where there isn't one on my 3.8L V6 engine. On pg 3-8 there's an arrow pointing to the "coolant temperature sensor" on picture 9.1, which is the one I replaced. Further, paragraph 9.1 states "...In the models covered by this manual, there is only one coolant temperature sensor, which functions as the indicator to both the Powertrain Control Module (PCM) and the instrument panel."

And the wiring diagram is useless as it's even titled "typical" and it doesn't have anything for a '99.

I've tried turning on the AC to get the fans to come on and that didn't work. I jumped the fan wiring harness and both fans work fine. I checked the new relay and it's fine.

<crescendo!>

I'm stumped. I'm about to just wire the fan so that it comes on with the ignition, but I'd rather not go that route.

Suggestions? TIA

 

Add power to the fans see if they work first then if they do replace that relay again under the air filter housing.

 

Hi Gromit,

I've recently had a check engine light with code P1491 Radiator Fan Control Relay Circuit (which has not come back after clearing codes). However, I did do a bit of searching on the web. One posting I came across (for a different model of Chrysler) indicated three things to check: PDC Fuse 40Amp; PDC Fan relay; and Fuse Box fuse number 10 which is 15Amp.

This suggests that Chrysler systems might have a couple of fuses as well as the relay (15A for signal to a relay seems a bit high, but 40A for fan main power looks right). Maybe have a look at those fuses. I don't know where they are on the vehicle.

Perhaps you could assist me...if I have to change my cooling fan relay, do you know where it is? I was told take off the bumper cover and it's behind there??? What colour relay am I looking for?

Good luck.

 

Sorry, I should have added that I did jump the fans from the battery and they both ran fine.

I tested the relay and the multimeter indicates that it works fine.

 

Thanks! I'll try that stuff tonight.

As for where the relay is located; remove the air filter housing (two big plastic things) and look on the wheel-well. It's bolted to it down there and has wires that go to the fan and back to...somewhere!

Hope that helps.

 

replace the relay my friend its a pulse with modulated relay and we are talking about the relay bolted to the frame under the air filter correct?

 

Fans should spin when the ECT sensor (there's one and you replaced it) reaches 200+ deg or the A/C is turned on and pressures are at spec. Since the fans won't spin in either mode either the PWM solid state cooling fan relay is at fault or the PCM isn't sending the command to the relay to turn on. The majority of the time it's the relay that has failed. I'll second Chrysler Techs thoughts. Here's how this pro tests the relay:
Would you like a 99 wiring diagram? Send me a PM with an email address included.

 

Gromit,

Thanks for the pointer for where to find the cooling fan relay. If my code comes back I know where to start hunting now.

I'm not a professional mechanic any more - haven't been a wrench for 25 years now. But when I was a wrench, generally I would not assume that a part that I had already replaced was faulty unless I could positively identify that to be the case.

Since you have new fans, which run when powered by a jumper, a new sensor and a new relay and you've tested your new relay too, then it seems logical to me that your problem is a power supply problem. The sensor is a switch that passes a small signal current to the relay, which is just a bigger more powerful switch to send a larger power current to the fan motors.

Check your fuses before throwing more parts at ones you've already replaced. If you don't know which fuse it is, then check all of the fuses for continuity with an ohm-meter or continuity tester - they can be easily tested in situ. I expect that there's more than one fuse box.

If the fuses check good, then remove the relay and check for main power to the relay with ignition on. I expect it'll be the thicker supply wire.

If the relay is pulse width modulated it may not be so simple to check for signal power....in the old days I'd have used a dwell meter on the scope for that, but that's not normally a shade tree tool. Perhaps the modern pros can advise best way to measure the signal to the relay at home?

Best of luck with it and keep us posted.

 

I haven't tried to test the relay that way. PM sent for the diagram!

Munro, this video shows exactly where to look and what the relay looks like.

I'm going to poke around for other fuses and then I'll attempt to test the relay the 'professional' way.

Have I mentioned how much I love working on vehicles?

<mumble>

 

there is no resetting a relay replace it