A/C CLUTCH SOLENOID

JEEPR did pass the time by typing:
> Initially it was but it is also doing it in the off selection, why?

Let's back up one step.. do you have automatic climate control?
If so then there are some other tests you can run to figure out
what's going on.

--
DougW

Doug
no auto climate control
what does defrost have to do with the ac compressor

--

Matt
0|||||||0
Tact is the ability to describe others as they see themselves
"DougW" > wrote in message
news:HQTfe.8145$Ri4.2260@okepread07...
> JEEPR did pass the time by typing:
> > When I pull the relay the solenoid de-energizes.
> > I'm thinking there is a short somewhere or chaffed wire, supplying maybe
a
> > ground for the solenoid to energize.
>
> That is the only thing it could be apart from the AC being on or the
> setting being defrost.
>
> The ECU provides a ground (transistor switched) to the relay. A short
> anywhere along that wire will energize the relay.
>
> Next step would be to disconnect the battery, and disconnect the harness
> from the ecu then ohm out the line. Watch that center bolt for the ecu
> plug, it's only there to hold the plug in, not to suck it in. Don't try
> to make the plug go in by cranking on the bolt, you will crack the ECU.
> That and it only goes hand tight, like a screw into plastic.
>
> In the meanwhile if you don't want it running you can simply yank the
> relay. Pulling the high/low pressure switches (either one) will set a
> fault code but will also shut off the relay by removing the power feed.
> A short in the ECU output to that AC relay won't hurt the ECU.
>
> --
> DougW
>
>

ECU?
what is that?

--

Matt
0|||||||0
Tact is the ability to describe others as they see themselves
"DougW" > wrote in message
news:HQTfe.8145$Ri4.2260@okepread07...
> JEEPR did pass the time by typing:
> > When I pull the relay the solenoid de-energizes.
> > I'm thinking there is a short somewhere or chaffed wire, supplying maybe
a
> > ground for the solenoid to energize.
>
> That is the only thing it could be apart from the AC being on or the
> setting being defrost.
>
> The ECU provides a ground (transistor switched) to the relay. A short
> anywhere along that wire will energize the relay.
>
> Next step would be to disconnect the battery, and disconnect the harness
> from the ecu then ohm out the line. Watch that center bolt for the ecu
> plug, it's only there to hold the plug in, not to suck it in. Don't try
> to make the plug go in by cranking on the bolt, you will crack the ECU.
> That and it only goes hand tight, like a screw into plastic.
>
> In the meanwhile if you don't want it running you can simply yank the
> relay. Pulling the high/low pressure switches (either one) will set a
> fault code but will also shut off the relay by removing the power feed.
> A short in the ECU output to that AC relay won't hurt the ECU.
>
> --
> DougW
>
>

Electronic Control Unit:
http://www.acronymfinder.com/af-quer...=ECU&Find=Find
God Bless America, ßill O|||||||O
http://www.billhughes.com/

JEEPR wrote:
>
> ECU?
> what is that?

That's what I kind of thought, would that be close to the powertrain control
module that I had indicated in original post as it is a 98 grand cherokee
4.0L

--

Matt
0|||||||0
Tact is the ability to describe others as they see themselves
"L.W. (ßill) Hughes III" > wrote in message
...
> Electronic Control Unit:
>
http://www.acronymfinder.com/af-quer...=ECU&Find=Find
> God Bless America, ßill O|||||||O
> http://www.billhughes.com/
>
> JEEPR wrote:
> >
> > ECU?
> > what is that?

would that be close to (same as) the powertrain control
> module that I had indicated in original post as it is a 98 grand cherokee
> 4.0L


--

Matt
0|||||||0
Tact is the ability to describe others as they see themselves
"JEEPR" > wrote in message
. ..
> That's what I kind of thought, would that be close to the powertrain
control
> module that I had indicated in original post as it is a 98 grand cherokee
> 4.0L
>
> --
>
> Matt
> 0|||||||0
> Tact is the ability to describe others as they see themselves
> "L.W. (ßill) Hughes III" > wrote in message
> ...
> > Electronic Control Unit:
> >
>
http://www.acronymfinder.com/af-quer...=ECU&Find=Find
> > God Bless America, ßill O|||||||O
> > http://www.billhughes.com/
> >
> > JEEPR wrote:
> > >
> > > ECU?
> > > what is that?
>
>

JEEPR did pass the time by typing:
> Doug
> no auto climate control
> what does defrost have to do with the ac compressor
>

In defrost mode the AC also runs even if the little lamp
doesn't turn on. Heat drives away the humidity and the
AC turns the humidity into water so it can drain out of the
cab.

--
DougW

JEEPR did pass the time by typing:
> That's what I kind of thought, would that be close to the powertrain control
> module that I had indicated in original post as it is a 98 grand cherokee
> 4.0L

ECU == PCM
Different name for the same thing.

Should be on the firewall behind the coolant overflow bottle
on the passenger side. Least that's where it is in the 93ZJ

--
DougW

Just so we all understand the solenoid is being energized even when the
ignition is off. That is the cause of the run down battery.

--

Matt
0|||||||0
Tact is the ability to describe others as they see themselves
"DougW" > wrote in message
news:HjVfe.8152$Ri4.4614@okepread07...
> JEEPR did pass the time by typing:
> > That's what I kind of thought, would that be close to the powertrain
control
> > module that I had indicated in original post as it is a 98 grand
cherokee
> > 4.0L
>
> ECU == PCM
> Different name for the same thing.
>
> Should be on the firewall behind the coolant overflow bottle
> on the passenger side. Least that's where it is in the 93ZJ
>
> --
> DougW
>
>

OK done some reverse engineering
the coil of the relay has a switched controlled ground and a 12v power
supply controlled through ignition sw I guessing as the 12v is not constant
the common contact on the relay has a constant 12v.
for the clutch solenoid to energize with ignition off, a ground would have
to be supplied to the relay and also a power source to energize the relay.
So theoretically if the ignition switch was not shutting off all the way
when key is extracted and the control was left on defrost this would cause
the problem as I had described. Not sure were the low pressure sw. plays in
this theory though, is it ignition controlled?
But I recall the solenoid engaging with the heater in off selection I'm
pretty sure.
If the PCM was having a melt down you think I would notice more symptoms on
other systems.
Ok I think I just talked myself out of understanding what the hell is going
on.


x1=12v sw
x2= gnd sw
C= common 12v constant
nc= normally closed to common
no= normally open or closed to common when relay is energized
| or __ = contacts

-- | x2 | nc | x1

__no

__C