QuestionQUESTION: Hi Roland,
First and foremost, thanks very much for all the help you provide on the site. It’s always good to read your posts. One which I read recently had to do with the cooling fans on a 2002 Sebring and as I thought about it, I wanted to ask you for your advice and counsel.
I have a 2003 Sebring GTC Convertible and I think the factory fan settings are way too high. I understand clearly that they are the default settings, and I also understand that the fans will come on “earlier” if the AC is on, but I don’t like how hot they let the engine get before going into operation when the AC is not on.
I like the engine to stay down around the “8:30” mark at least, and that’s where it stays if the fans are on, but otherwise it creeps close to 9. (these are approximate of course :) So my questions are somewhat simple:
1. Can I install a manual switch for the fans in a way (and in a position in the engine compartment) such that the onboard computer can be “bypassed” so that it won’t bring Error Codes up? I know if you try to do such a switch on the temp sensor/coolant air bleeder you will get Error Codes.
2. Even if the answer to the above is “Yes”, is either adding a larger/higher capacity fan cluster to replace the stock fan module, or, adding an additional fan (a 3rd fan) to the area between the fans and the engine something that can be done? I’m good with tools and could do most of the work myself but I don’t want to start with an ill-conceived plan.
As for the engine’s overall state, I’ve taken the oil pan off to see the sludge status and I’m good there, I’ve recently had a new 35-tooth water pump installed, I’ve flushed and cleaned the whole cooling system with distilled water, and I only use Mobil 1 and Zerex G-06 coolant. But I just want to keep this thing running cooler, always. Please advise, and thanks again for all your help!
ANSWER: Hi Joe,
The fans are supposed to come on low speed when the coolant sensor detects 220F and high speed at 230F. If you could get a temp reading at the time the fans are activated that would test whether the sensor is accurate. It is located at the thermostat housing and should read about 1,000 ohms resistance at that point. I don't have a diagram of the temp gauge so I don't know how to interpret what you describe as the readings of it. You could remove the coolant sensor and measure the resistance of it in a heated pan of water, up to the boiling point, to check its response.
While you could try modifying the fan controls, I would not do that without some better understanding of the temperature of the coolant at the instrument cluster gauge readings. It may be an inaccurate sensor or gauge. Other than the gauge reading the system is functioning properly, correct? As to the coolant, are you using a 50/50 mixture? If not, do that.
Roland
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dash gauge 
coolant recovery tank
QUESTION: Thanks Roland!
Yes I know what the factory settings are for the fans as I have all the Chrysler Sebring service manuals, but put simply I just want them to come on earlier.
Yes I did mix the Zerex 50/50 with distilled water, and yes, I do think the cooling system is in good functioning shape in all other respects.
I did a temp gun reading on the big exit hose that goes to the radiator (from the coolant air bleeder) but I don't think these laser guns are exact enough to draw too many conclusions as they can vary way too much from second-to-second. And unfortunately I didn't have an ohmmeter. I'll run by my mechanic's shop in the next couple days to see what he says about the temp sensor needing replacement or not though.
By the way, the "thermostat housing" you refer to is not where the sensor is on this engine; maybe you meant the coolant air bleeder though?...the temp sensor is part of that bleeder which is high up on top in the engine compartment. The thermostat housing (and the thermostat inside of it) is much lower and is way down low behind the dipstick and the alternator.
As for the gauge, I'm attaching a photo of it at it's hottest/highest reading before the fans come on to show what I mean. Please note when I say "9 o'clock" I am referring to the 2nd bold line on the gauge. And really that line is probably a little below exactly 9 o'clock - the exact 9 o'clock horizontal mark looks like it would be a line or two above that bold line I just referred to?(see picture).
But the point here is that the fans don't come on until the needle is at LEAST up at that bold line or above....and if you get out and open the hood at that point, it is really ridiculously hot inside the engine compartment. I think it's just way too hot before the fans actually come on. Now it could be that the actual temps they come on at might just be close to what they should be....220-230....but I'd like the fans to be running much earlier, like they do when the AC is on. The needle on the dash temp gauge drops down AT LEAST a couple of "lines" when the AC runs, and I'd just like to mimic that ALL the time, not just when the AC is running.
So even if the gauge is a little off, and replacing it would correct things a bit, I'd still like to know if installing a manual on/off for the fans is something that can be done without the OBC throwing Error Codes? Or if "upgrading" the fan module to a stronger/faster/better set of fans is something that can be done? I really don't care if I'm running the fans more than Chrysler says they should:) I think they did a really bad job design/engineering-wise with this 2.7L engine, and that's why so many of them end up with sludge in the oil pan that kills them.
Please let me know what you think, and thanks again!!
AnswerHi Joe,
I note that the temp at which the low speed fan is designed to come 'on' is 10 degrees cooler when the AC is activated than when it is not activated (210 vs 220). That is what explains your observation. Absent any tendency for the engine temp to operate consistently above the level you describe I would not advise you to install a manual fan control switch. The history of the 2.7 suggests that it would be better for it to operate the way it is now than to be running at a cooler temperature which I would believe would encourage more sludge to be generated. It would also then put the burden on you to operate the fans as needed which may prove to be a distraction, at best.
Roland
