My 1997 LHS 3.5 Liter radiator cooling fans cut in too late and cut out too soon. In idle, the guage creeps to middle of scale or higher. Checked all connections indicated in my FSM and also ran fans manually (they both work in both speeds). Relays are OK.
Is it true that these fans are also regulated by Intake Air Temperature Sensor, Output Speed Sensor and Transmission Oil Temperature Sensor? I'm inclined to try a new Intake Air Temperature Sensor, if somebody can confirm that this can affect the problem.
hey hank those early LH body fans had alot of problems with the ac high side pressure transducer and wiring which is mounted on the high sideac line at right bottom corner behind radiator. four wire plug. check it out
Checked out A/C sensor by turning "air" on and off. When 'on' the temperature drops slightly which is as expected. I'm still betting on the "Intake Air Temperature Sensor". Does anybody know whether this part has anything to do with the contol of the fans?
No they have nothing to do with those, it works strickly off the coolant temp sensor. What makes you think they cut in to late and out to early? have you checked the acuall coolant temperature with a scan tool to verify this? Is the sending unit that sends the signal to the gauge not working properly?
Thank you for your input Glen. Admittedly, I haven't checked the temp with a separate tool beside the reading on the dash guage but here's what I notice: When driving normally, the guage settles in nicely where it always has, a little below the center point of the guage. In the past, when in stop-and-go traffic the guage would remain there. Now (in stop-and-go) the guage creeps up beyond the center point of the guage at which point the fans finally cut in.
If the Coolant temp. sensor controls both the fans cut-in point and the guage on the dash, wouldn't the reading on the guage remain low even if e.g. the engine overheated? That's the part that has me stumped. Anyway, since everything else checks out (wiring, AC sensor, relays and the fans themselves), I guess I'll be replacing the coolant temp sensor. Still doesn't make sense to me though.
Cooling system is fine, else it wouldn't properly cool the engine under any circumstances. For argument's sake, what would be the symptoms if the "intake air sensor" was faulty and read higher than it should?
-Hank
P.S. Unlike some GM vehicles (where fans cut in as soon as the air is turned on), the LHS uses both the AC and temp sensors to determine the need for fan activity. BTW, switching the AC on does make the fans cut in slightly sooner but not soon enough.
The Air Intake Temp Sensor is not used for the A/C on a Chrysler Product. It's only purspose is to measure the temp of the air that is about to enter the combustion chambers. The PCM uses this sensor to compensate for changes in air density due to temperature
I guess I wasn't too clear about the A/C issue. I merely meant to say that the A/C sensor appeared to be working because it causes the fans to cut in at a slightly lower temperature.
I assumed the primary function of the Air Intake sensor had little to do with the fan operation directly, but as noted above, it does have minor influence (quote: "there is a small tie in at the pcm progamming that does look at the intake temp but just as a reference").
I guess, Glen, here's where I'm at. I'm confident my engine runs a bit too hot when the car is standing still and idling. I know this, because it never used to. I've checked all the connections, relays, fans etc. as suggested in my FSM. As I see it, the Coolant temp sensor can't be the culprit because then the guage in the dash would also be affected and it is not. (By this I mean that the guage also registers the higher temperature so I would think if it is working well enough to do that it should also send a turn-the-damn-fans-on signal to the computer module.) This leaves me looking for other devices, sensors or what have you that can throw off the signal from control module.
I would take this to a local dealer but I don't want to have to pay for an expensive fishing expedition that may not solve anything. (You may know the routine: try this sensor; flush the system; replace the thermostat; etc.) Maybe I'll just trade the car in which would be a shame 'cause it goes like the wind, rides great, handles well and looks pretty sharp!
The air intake sensor is not used for the A/C at all. The first thing to do if you think theres an overheating problem is to compare the acuall reading with a scan tool to your gauge on the dash. then find out what is right and what is wrong
You've already concluded that the gage is reading from the same sensor that controls the fans - and the gage agrees with the fan operation. Sounds like something is interfering with efficient cooling - like a clogged radiator or bad thermostat.
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
gage Pronunciation: 'gAj Function: noun Etymology: Middle English, from Middle French, of Germanic origin; akin to Old High German wetti pledge -- more at WED
1 : a token of defiance; specifically : a glove or cap cast on the ground to be taken up by an opponent as a pledge of combat
2 : something deposited as a pledge of performance Gauge
calculate something: to determine the amount, quantity, size, or extent of something It's quite difficult to gauge the distance accurately.
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I'd like to thank all of you for your input. As things stand I'm pretty much back where I started, i.e. throw myself on the mercy of the dealer's service department (where they have all the scan tools etc) and hope to hell I find a mechanic who can follow a logical sequence.
If my system needed a flush or a thermostat it would overheat all the time instead of ONLY when the fans are needed for cooling as in stop-and-go traffic. If my dashboard guage was unreliable it would read wrong all the time, not just when the fans are needed. Anyway gentlemen, wish me luck.
I'm not sure if you're flagging Hank's repeated misspelling of gauge/gage, or what you *think* is *my* misspelling of 'gauge' as 'gage'.
From Webster's New World Dictionary:
"gauge ...Also spelled *gage*"
Any questions? :)
Fact is, I am a technical writer - and 'gage' is used more often these days than 'gauge' - *and* for some reason, I have a mental block on the correct spelling of most words that have either 'au' or 'ua' in them (for example, I always have to look up spelling of 'guarantee', gauge', and 'guard' to see whether they're 'ua' or 'au') - perhaps Hank has the same problem. I was very glad the day that I realized that 'gage' was a perfectly acceptable alternative spelling of 'guage'.
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')
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