AC Gurus - I need your guidance - Blinking light (1 Viewer)

[TEXAS 57]

Hello all,

Having some issues and maybe someone can help. It's 100+ this week in the Houston, TX area and the AC is cutting out.

2002 LC with rear AC.

Blinking AC light - it's been happening for awhile but you could usually turn it off and turn it back on again and it would start working for the last 2 years. Wrote it off as a quirk.

About 2 weeks ago, the blinking light came on and we couldn't revive it. Then a pattern developed over the next couple days.

Over 92*, the light would blink and AC cut out. Pressing the button would reactivate for about 2-3 seconds then cut out again. After a few times it would stay on.
Then the AC would function fine for the first 10 minutes almost exactly then cut out with a blinking light.

History - Compressor, Condenser, Evap Core, Drier and Expansion Valve were replaced about 30-40,000 miles ago. No Changes.
A couple days after the issues, I tried swapping out the MG CLT relay with a known good one (I have 1999 LX470) and replaced the H/L pressure switch and no changes.

I have a set of gauges, vac pump, freon, and tools.

I saw a link to a Thread that said "AC Diagnostics" but the link was dead.

 

[hoser]

First check for HVAC diagnostic codes. From memory, it might be holding down the A/C button and Fresh/Recirculated button and turn on ignition. Count codes. Search Codes.

Also, if your 100 is on the verge of overheating, the A/C will also cut out. Check vehicle temps via Scan Gauge or anything other than the dash gauge. Clutch fan going out is the most common reason.

 

[ibrahim83]

Check for codes, then make sure you have enough refrigerant. Could be a bad compressor, specifically the rpm sensor in it.

 

[Malleus]

The A/C troubleshooting procedure is in the Resources section, in the 100 series FSM, pages 1300-1375.

 

[TEXAS 57]

First check for HVAC diagnostic codes. From memory, it might be holding down the A/C button and Fresh/Recirculated button and turn on ignition. Count codes. Search Codes.

Also, if your 100 is on the verge of overheating, the A/C will also cut out. Check vehicle temps via Scan Gauge or anything other than the dash gauge. Clutch fan going out is the most common reason.

Thanks. Those two buttons did it. Rear Defrost and Front Defrost blinking = Solar Sensor. Part ordered. (Edit: not fixed - see below post)

 

[TEXAS 57]

Well, it seems I skipped over the part that says to have vehicle outside so the solar senser was not the issue. Now, when running the diagnostics, I have the Rear Defrost and the Rear Fan Switch blinking which should mean everything is working fine. The outside temp display is also blinking (not sure if this means anything).

I cannot find any other info on the 3 dial AC switch diagnostics. I have the FSM for the LX470 but that AC panel has all buttons (not the MFD). I wanted to try the actuator check. I do have the online manual LC100 Workshop Manual - https://lc100e.github.io/.

I have checked the compressor lock sensor resistance and it Ohm'd out fine at 875 (I also checked an ac comp on the shelf and it was 861) (should be between 570-1050 @ 68F.)

I tried checking the Refrigerant Temp Sensor (on Compressor) and could not get a reading on either compressor (should be below 70 ohm at 68-86*F.

 

[TEXAS 57]

Does anyone know if there is a way to check the speed sensor?
I feel this could be the cause. Many times when I come to a stop (idle in gear) it will cut out.

Going to Florida in about 13 days....

 

[G-Cat]

Also, if your 100 is on the verge of overheating, the A/C will also cut out. Check vehicle temps via Scan Gauge or anything other than the dash gauge. Clutch fan going out is the most common reason.

Please make sure that your 100 isn’t on the verge of overheating. No A/C is super uncomfortable…but an overheated engine with resultant damage can be the end of the truck.

I only quote @hoser and reemphasize because the A/C cutting out is a symptom of high engine temps and you didn’t respond to this portion of his message.

If you are 100% sure that engine temps are normal/not an issue, then I digress and look forward to your fix for the A/C.

 

[TEXAS 57]

Please make sure that your 100 isn’t on the verge of overheating. No A/C is super uncomfortable…but an overheated engine with resultant damage can be the end of the truck.

I only quote @hoser and reemphasize because the A/C cutting out is a symptom of high engine temps and you didn’t respond to this portion of his message.

If you are 100% sure that engine temps are normal/not an issue, then I digress and look forward to your fix for the A/C.

Thanks for the notice. I did check with a thermal laser gun at the pump and temps are fine after 102* outside and long trips but forgot to post. Clutch fan was replaced a couple ten thousand miles ago as well but not related.

Oddly, it did not go out yesterday (103* on the way home, 35-45 min / 25 mile X2), and this morning it went out just after start up and pulling out of the garage. Turned it off for about a minute and turned it back on and worked perfect on the 35 min 25 mile drive to work.

Edit: AC Cut out on the way home after 20 min of driving. I could not revive it for 10 min., then as i am pulling into the neighborhood it started working again.
No real patterns.

 

[TEXAS 57]

I guess i will buy another Denso AC Compressor and put it on.

 

[TEXAS 57]

While waiting on the AC Compressor, I decided to clean out the Cabin Air Sensor. It was dirty but didn’t change anything. Ohm’d out correctly.

 

[TEXAS 57]

Ordered a Denso Compressor and it had been dropped during shipping. Called and got another one sent out and it came next day (thanks RockAuto). I am getting a nice collection.

Moved all the bracketry over from the original:

Put it in this morning. Evacuated and filled system.

I got the blinking light close to the end of the 3rd can. I had my wife throttle to 1500 rpm’s while filling. I could not get rid of the foam in the sight glass even after 3 full cans. I am afraid to put more in.
I took it on a typical drive afterwords and the system worked the entire time. Fingers crossed!!!

 

[TEXAS 57]

Welp... this sucks... Wasted $380 and a day on this...

Not a 1/4 mile from the house this morning and the AC light blinks and kicks the AC Light off and had to cycle a few times to get it to stay on...

Anyone have any ideas?

AC Gauge Pressures are fine.

 

[ceylonfj40nut]

Is the clutch engaging and disengaging when AC works and not when blinking? Check clutch circuit?

 

[TEXAS 57]

Is the clutch engaging and disengaging when AC works and not when blinking? Check clutch circuit?

Yes, the clutch has no issues engaging.

 

[ceylonfj40nut]

When blinking does clutch cycle?

 

[TEXAS 57]

When blinking does clutch cycle?

When the light is blinking the clutch will not cycle. Turning the AC control knob off then back on will allow the mag clutch to engage. Sometimes it will stay on, sometimes it will blink and not engage until cycled a few times.

 

[ceylonfj40nut]

AC relay?

 

[TEXAS 57]

AC relay?

I have swapped the MAG CLT relay and Heater Relay in the past with known good ones from my 99 LX470 and no change.

 

[TEXAS 57]

I am not sure if checking voltage on the pinouts would even help because it is such an intermittent issue.