93 F-150 AC Clutch will not engage

The AC clutch has to have power to engage. I would bet it doesn't. 35 PSI is not a lot of pressure for R134, unless you in a very cold place. Like about

Al

If Chuck's suggestion shows that the clutch is good, proceed to the following; Follow the wire(s) from the A/C clutch and see where it/they go. This will lead you to a switch that is operated by system pressure. The switch looks similar to an oil pressure sender. As the pressure increases and decreases, the switch alternates between open and closed. This system has replaced the old bulb and thermostat of years gone by because of it's simplicity. Remove the electrical connector from this switch to the clutch. Hook up your multi-meter and read voltage from the exposed pin to ground. With the A/C on, it should cycle between 12V an 0V every 20 seconds or so. If you only have a continuity tester, remove both wires from the switch an connect across both terminals. The switch should cycle between "open" and "closed" at the same rate mentioned before. If it does not, the switch is probably bad. Just grab the switch by hand and screw it out of the fitting. There is a shraeder valve behind it like a tire valve. That valve will automatically seal the system upon removal of the switch. A new switch is going to set you back about $30. Let us know how you come out.

if you have disconnected it, you won't see any voltage cycling.............................

If you only have a continuity tester,

Try reading it again. "Remove the electrical connector from this switch to the clutch. Hook up your multi-meter and read voltage from the exposed pin to ground. With the A/C on, it should cycle between 12V and

OK, I'm gonna be charitable here and run thru two different scenarios

result will be no cyclying, because you have removed the switch from the circuit

result will be no cycling, because the compressor isn't running

Back to you, Tom Edison............

Is there a positive and negative side on the compressor?

Thank Tyrone... I'll give it a try and let you know what I find.

Now it is my turn to return your charity.

I can see where I might have confused the issue by saying to remove the connector from the switch to the clutch. I should have said, on the wire that goes to the clutch, remove the connector at the switch.

Back to you Einstein.

The negative side of the compressor is ground. The positive wire will attach to the terminal on the clutch. To do a test of the clutch, all you need to do is momentarily jump a wire from the positive terminal of your battery to the terminal on the clutch. If it is working you will hear and see it engage. There is no need to have the engine running for this test.

if you break the circuit ANYWHERE, the clutch will no longer be in operation, and hence, no cycling can occur

to this point, I was willing to think perhaps I had mis-undestood your directions, BUT................

so now you claim that the switch will cycle (which is caused by pressures going up and down in the low side of the system), even without a compressor ???

I think perhaps you should read up (or better yet, take a look under the hood) before you make a TOTAL ass of youorself

On Mon, 09 Aug 2004 14:09:49 +0000, TranSurgeon rearranged some electrons to form:

Too late, he already did.

yeah, I thought that 'cycling even with no compressor' was pretty much a hoot

Wouldn't it just be a whole lot easier to check for voltage at the clutch. If available, the clutch is bad. If not available check for voltage on the positive side of the pressure switch. If available, just pull both wires at the pressure switch and check for continuity across the switch. This is a normally closed switch.

If not available check for voltage on the positive side of the pressure switch. If available, just pull both wires at the pressure switch and check for continuity across the switch.

This is a normally closed switch. ============ ============ MarshMonster gives his 2 cents....

Unless there's no preasure..... then it's normally open.

oo L O

Other than that.....your advice is sound, and better yet, the easiest to understand in the thread so far. Short,simple, and easy to do.

lol @ Tyrone

respectfully, ~:~ MarshMonster ~suggests unhooking the connector at the preasure switch first..and jumping across the terminals with a paper clip to see if the clutch even works~ ========

Regarding " The negative side of the compressor is ground. The positive wire will attach to the terminal on the clutch. To do a test of the clutch, all you need to do is momentarily jump a wire from the positive terminal of your battery to the terminal on the clutch. If it is working you will hear and see it engage. There is no need to have the engine running for this test." ==========$$$$$$$$$$$$============

I hate to butt into this thread but how on earth can you check the clutch operation without the motor running? Sure you might hear a click,but you wont see the compressor turn will you?so how do you know if it's smoked or not?Do it with the motor running and check that the compressor engages!

If you only have 35 psi in a dead system which it is if the clutch won't engage, you are probably low. That said, the clutch cycling switch should be closed around 40 psi or higher. At 35 psi, you probably don't have enough static system pressure to close the cc switch. You are probably in need of more refrigerant.

||Regarding " The negative side of the compressor is ground. The positive ||wire will attach to the terminal on the clutch. To do a test of the ||clutch, all you need to do is momentarily jump a wire from the positive ||terminal of your battery to the terminal on the clutch. If it is working ||you will hear and see it engage. There is no need to have the engine ||running for this test." ||==========$$$$$$$$$$$$============ || || I hate to butt into this thread but how on earth can you check the ||clutch operation without the motor running? Sure you might hear a ||click,but you wont see the compressor turn will you?

Sure you will. Clutch off, the pulleys run but the center does not. Clutch on, the center starts revolving. If the center is turning, it's likely the compressor is pumping. Texas Parts Guy

||On Sat, 07 Aug 2004 23:24:24 GMT, "Chuck Duchon" || wrote: || ||>I have a 1993 F-150 with a 5.0 liter engine. When I turn on the AC the ||>clutch on the compressor does not engage. I checked the fuse under the ||>dashboard and it is OK. I thought I might luck out and find that the system ||>was low on R134 (the previous owner had it converted from the old type ||>Freon). ||>

||>Bought a can of 134, system took a little it, and the gauge on the recharge ||>kit measured in the "full" range at 35 psi. ||>

||>Is it possible for me to diagnose/replace a bad compressor clutch or should ||>I just bite the bullet and take it to an AC shop? ||>

||>Thanks ||>

|| || ||If you only have 35 psi in a dead system which it is if the ||clutch won't engage, you are probably low. That said, the ||clutch cycling switch should be closed around 40 psi or ||higher. At 35 psi, you probably don't have enough static ||system pressure to close the cc switch. You are probably in ||need of more refrigerant.

So you short across the switch contacts to make the cltuch hook up and it will take more refrigerant.

Texas Parts Guy