A/C cool vs. the heat wolves

[Eddie Bauer Blue]

This has been one early season hot spring into summer weather here in southeast and I just recently got the A/C up and running again on daughter's 1996 E.B. 4L , replacing a leaking high pressure port hose line and a leaking low pressure switch on low port side. Kicks out nice cold air. But the heat wolves are out to eat this up.

The compressor does not seem to cycle off and on at all: it either is off manually, or on manually from the dash control. This can't be good for excess wear or additional heat to motor. (1) Cause of not cycling normally?

Running down the highway at mostly 70mph & 90deg ambient temp to deliver back her Explorer, I see the coolant temps are in excess range with A/C on but even with A/C off temporarily at 70mph, climbing a mild hill raises coolant temps back up over normal very quickly.

Radiator was replaced along with OEM thermostat last year, water pump is not dripping, original clutch fan seems solid, not wobbly...

(2) Whats my most likely secondary cooling problem?

Highway speeds should be like ram air cooling to a radiator.

 

[Big Z]

(1) possibly a failed pressure switch stuck in the closed position. Not the usual type of failure (usually they won't close when failed), but weirder things have happened. Have you watched the compressor at high idle? Say, 2000rpms? It's normal to have long clutch engagement durations at idle; high idle though, you should see more frequent cycling. (2) I'll shoot for engine coolant flow restriction. Possibly that new thermostat not opening fully or gummed up passages from prior use of a stop-leak product or otherwise neglected cooling system. I'd perform some flushes and see what happens, especially if your coolant is obviously dirty.

 

[Eddie Bauer Blue]

(1) possibly a failed pressure switch stuck in the closed position. Not the usual type of failure (usually they won't close when failed), but weirder things have happened. Have you watched the compressor at high idle? Say, 2000rpms? It's normal to have long clutch engagement durations at idle; high idle though, you should see more frequent cycling. (2) I'll shoot for engine coolant flow restriction. Possibly that new thermostat not opening fully or gummed up passages from prior use of a stop-leak product or otherwise neglected cooling system. I'd perform some flushes and see what happens, especially if your coolant is obviously dirty.

Thanks for the reply Big Z,
I just changed out the high pressure side switch and compressor still doesn't seem to cycle, though
not sure if it should; some import cars do not - Also swapped out the fan clutch and when A/C is on the temp still climbs on highway . I will do the high idle cycle observation. All parts in A/C system changed out except for low pressure port hose. A/C cools extremely well.

Looking to replace OEM Motorcraft thermostat again, though thermostat less than 18mo old, rad less than a year. Coolant is nearly pristine as it was totally changed along with radiator when original one failed; no stopleak clogging things, but good point.

 

[koda2000]

I think your compressor/compressor clutch may be the issue. Run a jumper wire from the battery to the magnetic clutch and see it that makes it click in. You can also try a VOM or test light on the wire to the A/C clutch to see if it's getting the signal to kick in. If no signal then your problem is electrical. If there is a signal the the A/C clutch and/or compressor is at fault.

BTW, there's a relay that turns off the A/C at wide-open-throttle (WOT relay). If you have the EATC automatic climate control the circuit board has been known to sometimes develop cracks in it's solder joints.

Set to the MAX A/C setting, the compressor should kick in roughly every 10 seconds. If your temp is going up, but only when you turn the A/C on, it leads me to believe the compressor may be bad.

If your temp is going up even with the A/C off, your water pump may be bad even though it's not leaking. If you don't maintain your cooling system regularly the impeller can rust away and not move enough water through the system.

My daughter's '00 Mountaineer with EATC stopped cooling with the A/C on this spring. While investigating, I discovered that once the vehicle was at normal operating temp the A/C was actually pumping out HOT air. That told me that either the blend door or the blend door actuator was not working. I removed the actuator and took it apart to find stripped gears inside. For the summer I used the large crescent shaped gear to hold the blend door closed. Now it's blowing nice, cold again. I'll worry about replacing the actuator in the fall.

 

[Eddie Bauer Blue]

More excellent very detailed points for us to follow up on, thanks koda2000

 

[Big Z]

One thing I'd try on that A/C is to unplug the low pressure switch & make sure it shuts the clutch off--then plug it back in & do the same thing with the high side switch to make sure it's taking into account the position of those switches in the a/c clutch cycling. If it stayed engaged with one of those unplugged then there could be bare wires completing the circuit regardless of the switch's position. I do think it's unlikely though and probably wouldn't worry too much about the clutch not disengaging especially if you've observed normal high/low pressures via manifold gauges. A properly charged system on some vehicles on a hot day will do exactly that: stay turned on.

 

[Eddie Bauer Blue]

UPDATE:
As I mentioned previously I replaced fan clutch and now the thermostat, one at a time - but temp still runs high but especially with A/C on, which doesn't cycle on-off-on unless i momentarily unplug one of the new pressure switches.

I will buy or borrow an infrared temp reader to see what the temperature is out of the top rad hose outlet to see what heat we actually are producing...

Because the idle rolls up and down and IAC solenoid replaced I do suspect intake manifold vac leaks after reading the forums here (it does occasionally set lean codes) - cant find any external leaks except for 1 small emissions hose, since repaired.

Can intake vacuum leaks cause hot engine running?

 

[Turdle]

ac will only remain off when "floor" is selected. It will cycle in all other modes, which is normal.

For your overheat, check that the lower rad hose is not soft. If it is, it can be collapsing from the water pump suction.

Also, often overlooked is the radiator cap. if it leaks at all, temps will spike.

 

[Eddie Bauer Blue]

Even though i changed rad cap with radiator 18 mo ago i definitely will swap out AND will check lower hose: you are correct about possibilty of collapse and impeded coolant flow.

Thanks for the useable tips!

 

[koda2000]

A radiator cap has nothing to do with your water temp. Changing it will not improve your overheating issue. A radiator cap raises the boiling point of coolant by 2-3 degrees for every pound of cap (a 16 pound cap, which is what you should have, allows about 48 additional degrees of coolant temp).

If your lower hose hasn't been changed in the last 5 years or so, that would be worth doing, along with the upper and bypass hose.

 

[Turdle]

A radiator cap has nothing to do with your water temp. Changing it will not improve your overheating issue. A radiator cap raises the boiling point of coolant by 2-3 degrees for every pound of cap (a 16 pound cap, which is what you should have, allows about 48 additional degrees of coolant temp).

If your lower hose hasn't been changed in the last 5 years or so, that would be worth doing, along with the upper and bypass hose.

water temps above 220f are normal under stressful conditions. If the cap leaks this will cause a spike due to loss of pressure, and boil. I know this for fact, as I had this happen to me.

 

[Turdle]

http://www.cgj.com/2013/05/14/how-does-a-radiator-pressure-cap-work/

Coolant under pressure absorbs more heat. Loss of pressure can indeed cause spiking.

edit, to add to this.

If there is debris in the reservoir tank, that is very bad. That brownish film down at the bottom comes off in chunks. Since the coolant return hose is located at the bottom of the reservoir, these are the first things to get sucked back in. A common thing is to find a clog down there, which allows coolant to flow in to the reservoir , but not enough get back out to the radiator quickly enough . It almost becomes a one way valve.


All of the 2nd gens I have owned I had to remove the reservoir completely to wash this crud out because it clogs the drain even while you try to rinse it out with the hose off. And you can't get a shop vac down there real good,

 

[Eddie Bauer Blue]

ac will only remain off when "floor" is selected. It will cycle in all other modes, which is normal.

A/C indeed turns off in "floor " and " vent" modes and comes on but constantly seems to stay on in all the other modes.