Lump in Idle; 01 PT Cruiser

My beloved PT Cruiser with about 90,000 miles works to perfection; almost.
With the air running I experience a serious lump in the idle, perhaps once
per sec, or so. With the air off, and the car in or out of gear the lump is
mostly gone, at least not noticeable. Yes, it has new plugs and wires, and
the filters are new and the throttle body has been cleaned.

Recently I had to have the air conditioning recharged; twice. First charge
lasted just 3 days. It is now holding a charge and cooling more than
adequately, for about a week. Don't know if this was related.

Any suggestions?

Richard.

 

Does your radiator fan come on as soon as you turn the A/C on?


Glenn Beasley
Chrysler Tech

 

Perhaps not. What does this tell us?

Richard

 

You say perhaps not? it either is or isn't.

Glenn

 

Hi...

Absolutely not trying to hijack the thread, but just because I'm
intensely interested throwing in what mine does for what it may be
worth...

(94 lhs, in every respect just like brand new

And if "lump in idle" is the word, mine has it too... very noticeable
idling at a drive thru; quite noticable driving very slowly.

"lump in idle" in this case would be the engine rpm's dropping at least
100 rpm (first time you'd bet it would be going to stall), the tach
dropping, and surprisingly the interior fan slowing a lot. All for just
a second, then all comes back to normal, only to repeat a couple of
minutes later. I can live with it

However, the fans don't come on immediately. Sequence at idle and
hood open is the compressor engages. 10 seconds later the fans start.
Fans run only 3 or 4 seconds, then quit. This repeats at about two or
three minute intervals.

The owner's manual says the AC has a sight glass - like in the olden
days - but I sure can't find it. Anyone know where it might be?

And if it means anything, on a 90F day at start up the vents ouput
air at about 45 to 50 degrees idling.

Take care.

Ken

 

The owners manual shouldn't have anything in the about a sight glass because
it doesn't have one!! your probably referring to a repair manual such as
Chilton or Motor manual. Junk Manuals!! The PT cruiser will do this is the
compressor kicks out due to extreme high pressures, (normally due to an inop
fan) and when the pressure drops to allow the compressor to kick back in it
puts a huge load on the 4cyl Engine and it is very noticeable. You have a 6
cyl and normally not that noticeable when the compressor kicks in and out.
It would be hard to say what you are feeling with the LH If you are loosing
a cam or crank sensor intermittently you may be feeling that.
sorry not much help

Glenn Beasley
Chrysler Tech

 

You say perhaps not? it either is or isn't.

It isn't! But it does come on after a while.
Are you on to something?

Richard

 

Replace the fan assemble. The motor for the a/c is not coming on when the
a/c is turned on. IT IS SUPPOSED TO!! At idle your a/c should not be blowing
cold and will cycle on and off with extreme temperatures/pressures. At
highway speeds the a/c will work and blow cold due to force air across the
condenser. When you say it comes on after awhile what you see coming on is
the coolant temp sensor requesting that the 2nd stage of the motor to turn
on. If that stage goes out you will have an overheat condition. You do not
want this engine to go into a severe overheat condition or engine damage
could occur.

Glenn

 

The motor for the a/c is not coming on when the a/c is turned on; this has
been confirmed. But when I bypass the high speed fan relay the high speed
function on the fan comes on. Since this relay is controlled by the computer
I don't see any choice but to bring it into a dealer to figure out the
problem. These are not the "good old days" were it was possible to figure
these things out on your own. Thanks for all the guidance.

Richard

 

There should be TWO relays -- high and lo speed relays for the fans.
What Glenn suggested (and this sounds perfectly reasonable) that in
the fan assembly has the low speed circuit burnt out somehow.

You can test this assumption by "bypassing" (be careful how you do
that as not to burn out the computer, etc) the low speed "function".
My guess that the fans won't come on, which will confirm Glenn's
diagnosis of a bad fan assembly/wiring related to it.

Hope this helps,

Alex

 

There should be TWO relays -- high and lo speed relays for the fans.

The low speed fan works, the vehicle does not overheat. The high speed
function did not come on with the air-conditioned. I confirmed that it
worked by bypassing the high speed relay.

The Chrysler tech hooked it up to the computer and reported to me that I
needed a new fan assembly and a new wire harness for $500.00 since the
dealer's computer could only get the high speed fan to run at a low speed. I
told him I did not think that was correct since I could activate both fan
speeds, even though the computer code reader could not confirm this. I
suggested that he check the pressure of the system. He then found the high
side way too high and adjusted it to spec. He then found the low side too
low. He then said that I needed a new part for the air conditioner system
since a tube with a restrictor was too restricted, all for about $300.00
with no credit for the diagnosis fee of $85.00.

Something does not add up. Why would the car's computer not be telling the
high speed relay to turn on with the compressor? Too much pressure; I don't
see it. To much tube restriction; I don't see it. And why would the dealer's
computer only be able to turn on the high speed fan and get a slow speed
response?

By the way, the air conditioning is nice and cool during this situation.

Richard

 

I know someone's going to gack when I say this but I'm going to say it
anyway.

For 50 cents of wire you can wire the fan relay to be on high all of the
time.
It won't hurt anything. Perhaps cost a bit of mileage. Wire it this way
for
the summer. Then take the wire out in the winter.

In all liklihood the A/C system will leak in another 3-5 years due to simple
age,
or the compressor will burn out, and then you will have to spend some money
to fix it. You can get the fan fixed then.

Ted

 

typical dealer bullshit take it to a local shop and get it fixed right the first
time

 

"Typical dealer bullshit take it to a local shop and get it fixed right the
first
time."

First problem is that the Desk guy you are forced to deal with do not fully
and accurately communicate what he is told to the service tech. Then the
service tech does what Chrysler procedures tell he to check about the fan
not running and does nothing further to confirm that perhaps spending the
recommended $500 for a new fan and wire harness may not be needed. Gerrrrr.

Richard