LHS Cooling Fans

Discussion in 'General Motoring' started by Hank NB, Nov 7, 2005.

  1. Hank NB

    Hank NB Guest

    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.

    Does anybody know?


    Hank NB, Nov 7, 2005
  2. Hank NB

    philthy Guest

    the fans are run at 229 degrees and when ac is called for and it runs thru the
    pcm and gets it's info from the coolant temp sensor and campares it to other
    philthy, Nov 9, 2005
  3. Hank NB

    santino1 Guest

    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
    santino1, Nov 10, 2005
  4. Hank NB

    Art Guest

    Mine were replaced in 94 on my LHS. I would have thought they would all
    have been replaced long ago.
    Art, Nov 10, 2005
  5. Hank NB

    Hank NB Guest

    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?
    Hank NB, Nov 11, 2005
  6. Hank NB

    maxpower Guest

    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?

    Glenn Beasley
    Chrysler Tech
    maxpower, Nov 11, 2005
  7. Hank NB

    Hank NB Guest

    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.


    Hank NB, Nov 12, 2005
  8. Hank NB

    maxpower Guest

    I dont see that being a problem
    maxpower, Nov 13, 2005
  9. Hank NB

    philthy Guest

    there is a small tie in at the pcm progamming that does look at the intake temp
    but just as a reference but does not control the fans in any way. run the ac and
    see if both fans come on if they do then that part of the curcuit working
    if still no luck have the engine cooling system reversed flushed to see if it
    removes the debris that might be clogging the little coolant holes in the head
    philthy, Nov 13, 2005
  10. Hank NB

    philthy Guest

    the coolant temp sensor justs reports to the pcm what the temp is and the pcm
    assigns the job of turning on the fans after it gets some other imputs
    philthy, Nov 13, 2005
  11. Hank NB

    Hank NB Guest

    Thank you "philthy",

    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?


    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.
    Hank NB, Nov 14, 2005
  12. Hank NB

    maxpower Guest

    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

    Glenn Beasley
    Chrysler Tech
    maxpower, Nov 14, 2005
  13. Hank NB

    Hank NB Guest

    Thank you Glen.

    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!

    Hank NB, Nov 15, 2005
  14. Hank NB

    maxpower Guest

    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
    maxpower, Nov 15, 2005
  15. Hank NB

    Bill Putney Guest

    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')
    Bill Putney, Nov 15, 2005
  16. Hank NB

    maxpower Guest

    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
    1. calculate something: to determine the amount, quantity, size, or extent
    of something
    It's quite difficult to gauge the distance accurately.
    maxpower, Nov 15, 2005
  17. Hank NB

    Hank NB Guest


    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.

    Hank NB, Nov 15, 2005
  18. Hank NB

    Bill Putney Guest

    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:

    ....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')
    Bill Putney, Nov 16, 2005
  19. Hank NB

    maxpower Guest

    I learn something every day
    maxpower, Nov 16, 2005
  20. Hank NB

    Steve Guest

    Why? I've never had a problem with the AC transducer on my '93 LH. They
    don't get much "earlier" than that....
    Steve, Nov 16, 2005
Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.