A/C blowing cold, then hot, then cold | Replaced fan clutch fluid - same

[dranven]

Hey guys,

Recently my '97 started blowing cold a/c for a bit, then hot, then cold again, then hot. Over the past couple of months, the duration it blows hot is longer and begins sooner. It's been about 6 years since my Eaton fan clutch was serviced by ToolsRUs. I just pulled it out this week, drained it for 3 days and refilled with 15k cst fluid. Took it for a drive. Nothing has changed.

Any ideas what to check next?

 

[ceylonfj40nut]

Your Evap core might be freezing up. Put some gauges on it and report pressures. Is your compressor cycling?

 

[CJF]

Pretty sure the most common cause for that is a bad expansion valve.

 

[davesax36]

Pretty sure the most common cause for that is a bad expansion valve.

Where's that?

 

[scottryana]

Yep I second expansion valve it is behind the dash in the passenger's footwell area.

 

[dranven]

Thanks guys. The compressor is cycling. No bubbles in the viewer near the battery. I've been reading the FSM a bit to prepare. I'll go rent a gauge set later today or tomorrow.

To replace the expansion valve, the FSM (beginning at AC-24) states to disconnect those two lines at the passenger firewall. Do I need to discharge the system or anything before doing so? Never messed with any a/c components before.

 

[scottryana]

Yes you would need to evacuate the entire system, I would also replace the dryer when you did it. Best to have an AC shop do the work so they can capture the freon and recharge the system.

Thanks guys. The compressor is cycling. No bubbles in the viewer near the battery. I've been reading the FSM a bit to prepare. I'll go rent a gauge set later today or tomorrow.

To replace the expansion valve, the FSM (beginning at AC-24) states to disconnect those two lines at the passenger firewall. Do I need to discharge the system or anything before doing so? Never messed with any a/c components before.

 

[flintknapper]

Thanks guys. The compressor is cycling. No bubbles in the viewer near the battery. I've been reading the FSM a bit to prepare. I'll go rent a gauge set later today or tomorrow.

To replace the expansion valve, the FSM (beginning at AC-24) states to disconnect those two lines at the passenger firewall. Do I need to discharge the system or anything before doing so? Never messed with any a/c components before.

Let's not 'assume' anything just yet.

Get a set of gauges, hook them up (if you need to know how...let us know). We need to know the ambient temperature when you do the test and the high and low side readings. Let the A/C run a few minutes to stabilize before taking the readings.

Your pressures (and any movement of the gauges) might give us some direction.

To answer your question though: Yes, the system must be evacuated before opening the system anywhere. Also IF your TXV needs to be replaced...you'll have to remove the entire evaporator box and evaporator to access it. So....best to make sure that is the issue before diving in.

A low refrigerant charge can also cause the evaporator to freeze up (blow cold for awhile, then hot until it becomes unfrozen, then it starts all over again).

 

[Jgrauman]

Just another thought. Mine would do this as well as in the winter would go from hot to cold and back again. Mine was the temp control slider. There are 4 solder points on the back of it, I found on here where someone discovered they crack. I re-soldered last year and haven't had a problem since.

 

[ZackR]

As others have said, expansion valve. The same thing happened to mine after repairing a bad line and refilling with refrigerant (cool, then warm).

Pulling the evaporator to access the expansion valve isn't too bad and it gives you an opportunity to clean it out.

Clean your evaporator !!

 

[L2k]

Experienced a similar situation last summer. The compressor clutch was out of tolerance. Removed the clutch and a couple of shims. Hasn't had anymore problems. Check the FSM for the correct gap. Worthwhile checking.

 

[Tools R Us]

What is the coolant temp when this is happening?

 

[CJF]

What is the coolant temp when this is happening?

Oh yeah, duh; good question.

 

[danthman114]

cold when driving and warm when stopped?

 

[dranven]

Hey guys,

It's been a busy week, family in town, some trips to the Grand Canyon, Flag, Sedona, etc so I haven't had a chance to respond; however, the situation has been resolved.

To answer Kevin's question above, ECT is reading ~194 while driving around in the AZ summer heat. I did a coolant flush since it had been a while...

So, as far as the problem, I'm not sure if perhaps when replacing the fan clutch fluid it needed some time to do its job. What I did in sequence was:

-Changed fan clutch fluid (15k)
-Immediately drove for an hour (problem not resolved)
-Let it sit overnight
-Flushed coolant next day
-Immediately drove it for 2.5 hours (problem resolved!)