Intermittent AC Issues '94 fzj80 (1 Viewer)

[Kungpaodog]

AC usually will run for one to five minutes and then shut off. I haven't been able to get it to come back on until another day.

Last week I took the Cruiser to work (I almost never commute with it), about 20 miles one way, mostly between 55 and 65 mph. Didn't try the AC in the morning. Ran errands at lunch and the AC worked for about sixty minutes of drive time with three stops, mostly highway. It ran icy cold after work for another hour, with some stop and go traffic and one quick stop. Next morning icy cold, too cold for the morning. Icy cold on the way home.

Today drove about 45 minutes to Denver, no AC, but it worked great on the way home, again mostly highway both ways.

The idle up circuit functions when the AC blows hot.

Where do I start? I'll have to buy tools to do any trouble shooting other than ohm checks or visual inspections, so let's think this out before throwing parts and tools at it!

 

[cjmoon]

Not sure if it's the same problem but if your condensor is not condensing the pressure and heat will build. I added a 13" fan pushing through on the passenger side. It helps. Mine would some times cycle on and off with poor performance some times worked great. Your return line should be cold when properly working.

 

[Kungpaodog]

Not sure if it's the same problem but if your condensor is not condensing the pressure and heat will build. I added a 13" fan pushing through on the passenger side. It helps. Mine would some times cycle on and off with poor performance some times worked great. Your return line should be cold when properly working.

I suppose I should go in there and clean it to be sure, but does it make sense that the AC seems to work better after the truck has had a recent heat/cool cycle?

 

[Landseer]

If the condenser were getting insufficient airflow the AC would be consistently warm. The best way to diagnose AC issues is to get some gauges and check the pressures. I would bet that the compressor clutch is failing sporadically, easiest way to diagnose is to check the pressures when the AC is blowing hot.

 

[Kungpaodog]

If the condenser were getting insufficient airflow the AC would be consistently warm. The best way to diagnose AC issues is to get some gauges and check the pressures. I would bet that the compressor clutch is failing sporadically, easiest way to diagnose is to check the pressures when the AC is blowing hot.

That makes some sense. What causes sporadic clutch failure? Bad temp sensor? Low Freon?

 

[Landseer]

Its possible that the electronics controlling it are failing but its likely the clutch itself. The fact that the engine idles up even when the AC blows hot indicates that the computer thinks the AC system is ok. If the pressure were too low (low freon) the system would shut off and would not idle up. When the AC is not working pull the wire off the clutch and check the voltage to ground, if its zero then something electrical is broken. I think the voltage should be 12v (can someone confirm this?), if it is 12v and the high and lowside pressures are basically equal (in the absence of gauges AC blowing hot) then the clutch itself is bad (the compressor could technically be bad but that likely wouldn't give the intermittent symptoms). You can probably get a new clutch from Toyota but a brand new Denso compressor with clutch is $190 from Rockauto, probably worth switching out the whole thing.

 

[Kungpaodog]

Its possible that the electronics controlling it are failing but its likely the clutch itself. The fact that the engine idles up even when the AC blows hot indicates that the computer thinks the AC system is ok. If the pressure were too low (low freon) the system would shut off and would not idle up. When the AC is not working pull the wire off the clutch and check the voltage to ground, if its zero then something electrical is broken. I think the voltage should be 12v (can someone confirm this?), if it is 12v and the high and lowside pressures are basically equal (in the absence of gauges AC blowing hot) then the clutch itself is bad (the compressor could technically be bad but that likely wouldn't give the intermittent symptoms). You can probably get a new clutch from Toyota but a brand new Denso compressor with clutch is $190 from Rockauto, probably worth switching out the whole thing.

Great info, thanks. I've never been into an automotive AC compressor; is it possible to open it up and repair, or is this best treated as a sealed unit?

 

[Landseer]

I've heard shops used to open up compressors and repair them but that era is long gone. You're compressor itself is almost certainly fine, it just needs a new clutch (assuming the clutch is in fact bad), unfortunately the clutch is not repairable. You can try and get a new clutch from Toyota, I'm not sure how difficult it is to replace the clutch with the compressor still in the truck. It would save you having to evacuate and recharge the system.

 

[1972FJ55]

Look at the front hub of the compressor when the A/C isn't working and see if the hub is spinning. If it is, the it's possibly the expansion block. If it's not spinning, then check to see if power is being sent to the clutch. If it has power, the clutch coil may be bad, or the clutch gap is to wide. If there's no power to the clutch, it will require troubleshooting to determine what is interrupting power. Expansion blocks are known to work intermittently.

 

[Kungpaodog]

Thanks for the advice. I'll probably do some troubleshooting this weekend.

I've been commuting with my Cruiser to try to get the problem to come back, but it works just fine again today. I think the key is I need to park it for a few days. I did have it parked outside, nose downhill, in a lot of rain this spring and it collected water in the body or frame that ran out when I drove onto flat ground, so maybe some water also ran into the compressor and it got a little corroded?

I found this post on another board about another make, but the basics should still apply:
"Just thought I'd share my problem/solution in case it helps anyone else with intermittent air conditioning .

I was having a problem with my a/c systemeither working or blowing hot air. The engine revs consistently went up when the air-conditioning was activated suggesting that the switch and relay was okay.

When I started poking around, the pressures seemed pretty good (within the range of acceptable anyway - I added a tiny by of refrigerant to the system to bring the low side up). But the most obvious thing was that the clutch (in front of the compressor) would engage when the system worked, but wouldn't when the system failed. I then confirmed that the relay/pressure switch was working by checking that the clutch was getting power (simple light probe). Because it was, I could rule those out. The clutch turned freely and the pulley/belt looked fine. I then sent power directly from the battery to the clutch to see if it would engage. It wouldn't engage which made me think that I'd need a new a/c clutchand maybe compressor. But -- and here's the important thing -- I could feel the electromagnet in the clutch turn on and off. My steel screwdriver would be pulled to the clutch whenever I gave it power. I was worried that theclutch magnet coilhad shorted or something like that, but if the magnet fired up, it should just be a physical blockage. To solve the problem, I used a screwdriver to push the clutch in and out (the travel is about a 1 mm to 1.5 mm). I repeated this to all sides of the clutch to ensure that it moved as freely as possible. I then used compressed air to blow out dust from the inside of the clutch and sprayed a little oil in there to keep things lubed up.

In the end it worked fine and I now have a reliable a/c systemand it didn't cost me anything. Hope this is helpful to someone out there."

 

[Kungpaodog]

Look at the front hub of the compressor when the A/C isn't working and see if the hub is spinning. If it is, the it's possibly the expansion block. If it's not spinning, then check to see if power is being sent to the clutch. If it has power, the clutch coil may be bad, or the clutch gap is to wide. If there's no power to the clutch, it will require troubleshooting to determine what is interrupting power. Expansion blocks are known to work intermittently.

I had AC failure on the way home from work and the hub on the compressor was spinning when the AC was on, and the hot and cold lines were both warm.

Looks like I can get a Denso dryer (might as well while the system is open) and expansion valve for about $40 from Rock Auto. Then I'll probably pay a shop for a recharge. Is there anything else I should check before I get parts?

 

[Landseer]

You'll need some PAG 46 oil and o-rings for the firewall connections (the Rockauto o-ring kit works well). You'll want to have a shop evacuate the system for you so you don't vent R-134a into the atmosphere when you open the system. Get a quote on how much it will cost to refill the system, a vacuum pump and gauges are surprisingly cheap if you opt to do it yourself, personally I'd rather spend $ on tools than at a shop.

Only other thing I can think of is to take a look at your condenser, if its original and not looking so good you could consider replacing it while the system is open.

 

[Kungpaodog]

Thanks for the tips! I know a vacuum pump can be had cheap and I can borrow the gauges from a friend.

Can you take the old 134a to a shop for recycling?

 

[1972FJ55]

I'd replace all the o-rings in the system while you've got it apart, including the hex-shaped gasket under the plate on the compressor where the hoses attach. Vacuum a minimum of 45 minutes, then let it set for a few to see if it looses vacuum. Since you'll have the evaporator core out, it's a good time to clean off the lint, dog hair, leaves, etc.

 

[Landseer]

Can you take the old 134a to a shop for recycling?

A standard vacuum pump does not allow you to recover the refrigerant. You'll have to take the LC to a shop where they have a special machine that will remove and store the R-134a (and potentially reuse it). With the system now empty you can open it up without releasing any R-134a.

I'd replace all the o-rings in the system while you've got it apart, including the hex-shaped gasket under the plate on the compressor where the hoses attach. Vacuum a minimum of 45 minutes, then let it set for a few to see if it looses vacuum. Since you'll have the evaporator core out, it's a good time to clean off the lint, dog hair, leaves, etc.

Some of the o-rings are pretty inaccessible and not worth messing with. In addition to the compressor manifold gasket already mentioned the o-rings on the condenser are worth doing and easily accessible. Also, add some UV dye to the PAG oil (or get PAG oil with dye already in it), this will make finding any future leaks much easier.

 

[TX Cruiser]

Check the tension on the belt, check for discoloration on the clutch, clean the clutch friction plates with brake clean or the like, remove a spacer from the clutch if need be (adjust air gap), then suspect the expansion valve.

You have one of the best compressors ever made, if not the best, but they sometimes do need a new clutch assembly. There are vendors that sell just the assembly.

I have had a new Denso expansion valve (FZJ80) fail, under vacuum. It never even saw refrigerant. Luckily, I had an aftermarket TXV on hand, and that Mudder left happy.

 

[Kungpaodog]

Check the tension on the belt, check for discoloration on the clutch, clean the clutch friction plates with brake clean or the like, remove a spacer from the clutch if need be (adjust air gap), then suspect the expansion valve.

You have one of the best compressors ever made, if not the best, but they sometimes do need a new clutch assembly. There are vendors that sell just the assembly.

I have had a new Denso expansion valve (FZJ80) fail, under vacuum. It never even saw refrigerant. Luckily, I had an aftermarket TXV on hand, and that Mudder left happy.

Thanks for the advice. Can that be done on the vehicle? It looks pretty tight in there, and the hub certainly looks like it spins up just fine. Would the clutch still be suspect even when the hot and cold AC lines are both hot at the firewall while the hub is spinning?

 

[1972FJ55]

Probably easier to diagnose if you hook up some gauges. When it's not blowing cold and the hub is engaged, see if the low-side pressure is at zero or in vacuum. If it is, the expansion is bad.