AC behaviour in hot conditions?

dgeist · **Posted:** Thu Jul 29, 2010 3:27 pm

So, I'm driving back from a short out-of-state trip this past weekend and the ambient temps on the Interstate are around 98-100 degrees. I noticed what sounds like a mechanical straining on the climate control fan. The air temp coming out (all the way cold and fan on "2) were as cold as normal, but the airflow seemed to be restricted.

We stopped at a rest-stop for a little while and parked in the shade and and the performance seemed to be a little better when we got back on the road.

Question is: Is this typical of running in REALLY hot conditions? and... what exactly is going on? Why would the fan strain when it was hotter? Perhaps low current coming out of the alternator since the AC compressor was working harder? I never had any other electrical issues and I know the alternator and (new) red-top both tested fine recently...

Just wanting to know if I need to go look for what's wrong or if this is the price you pay for driving 70 in sweltering heat.

Dan

ebbnflow · **Posted:** Thu Jul 29, 2010 3:48 pm

Sounds like it could be the blower resister taking a poop. When mine went bad, I lost settings 1 and 2. I have read that it could be any of the 1, 2 or 3 that can go and you need to replace it. It cost me $20 from Rock auto with shipping included. It took 10 minutes to swap.

Does your blower work on any of the other settings?

dgeist · **Posted:** Thu Jul 29, 2010 3:58 pm

It works on all the settings. The issue was temporary and seems better now, but I'm worried the temporary symptom is indicative of a permanent issue. A resistor wouldn't fail "part way" like that, so I doubt it's the issue...

dritchie · **Posted:** Thu Jul 29, 2010 5:14 pm

Maybe your evap was icing up and restricting air flow. Make sure the vent control is on recirculation mode. That will keep the hot HUMID air out of the car.

Dave

flash7210 · **Posted:** Thu Jul 29, 2010 6:06 pm

Yup, that was your evaporator freezing up. Happens to me quite often and only in recirculate.
When I flip it over to outside air, the hotter outside air gets it melting quicker.

In any case, when you notice this condition turn the A/C off until warmer, forceful air comes
out the vents. Then turn the A/C back on and resume whatever your previous settings were.

Some cars have a sensor that turn off the compressor when the evaporator freezes.
I guess our KJs do not.

warp2diesel · **Posted:** Thu Jul 29, 2010 6:20 pm

dritchie wrote:

Maybe your evap was icing up and restricting air flow. Make sure the vent control is on recirculation mode. That will keep the hot HUMID air out of the car.

Dave

X2

If the AC acts like it is nuts, squeeze the three plugs over by the TCM back together, that was all that was wrong with mine when it acted nuts and then quit. Better than shelling out a bunch for Evac & Recharge and a bunch of parts you don't need.

FastSRT8GC · **Joined:** Mon Jan 04, 2010 9:52 pm **Posts:** 55

I live in FL and I am having a similar issue. When really hot it has a very hard time getting cool. It seems to me that it is stuck in between outside air and recirculation. Even smells from out side seem to come in under recirculation.

Wonder if the vacuum controls are messing up.

AZ CRD · **Posted:** Thu Jul 29, 2010 9:51 pm

I live in the hot capitol of the US. The AC in this vehicle seems relatively poor. I haven't experienced a fan speed change, but it's annoying that the AC compressor cuts out under very little acceleration.

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

The AC cut-out for acceleration can be changed in the ECU if desired. In stock form the AC cut-out was necessary to allow the CRD to get out of its own weight in high temp situations when pedal demand reached a certain level. The max cut-out if doing a full throttle acceleration is around 8 seconds. Where you live the AC performance is borderline with the electric fan set-up on the CRD. You could add some foam seals in between the condenser, CAC and radiator to obtain improved flow through the cooling pack...in stock form it is less than ideal. The pusher fan does not provide enough cfm of flow for the harshest conditions. Also, try a seal around the pusher fan ring to assist with having more flow going through the condenser.

AZ CRD · **Posted:** Sat Jul 31, 2010 8:26 am

GreenDieselEngineering wrote:

The AC cut-out for acceleration can be changed in the ECU if desired. In stock form the AC cut-out was necessary to allow the CRD to get out of its own weight in high temp situations when pedal demand reached a certain level. The max cut-out if doing a full throttle acceleration is around 8 seconds. Where you live the AC performance is borderline with the electric fan set-up on the CRD. You could add some foam seals in between the condenser, CAC and radiator to obtain improved flow through the cooling pack...in stock form it is less than ideal. The pusher fan does not provide enough cfm of flow for the harshest conditions. Also, try a seal around the pusher fan ring to assist with having more flow going through the condenser.

Thanks for the advice. Had I not already invested in InMotion/SEGR I'd give you guys a try and have you eliminate that AC cut-out.

bakersoil · **Joined:** Fri Jul 23, 2010 5:43 am **Posts:** 68

My A/C would tend not to work right when temps got above 95 degrees. Lower than that it would freeze you out of the vehicle. I could feel the air from the vents change temperature about ever 6 seconds or so while cruising around 60-70 mph. Turned out to be the low pressure switch. It now works great with 91k on the clock.

BlackLibertyCRD · **Posted:** Mon Aug 02, 2010 12:21 am

Getting low on freon is another reason it could ice up. Adding a can of freon should cure it.

dgeist · **Posted:** Mon Aug 02, 2010 2:59 pm

BlackLibertyCRD wrote:

Getting low on freon is another reason it could ice up. Adding a can of freon should cure it.

..or 134a (was the KJ ever made with freon?). I wouldn't be surprised if it's lost a little, it's been untouched for more than 5 years.

flash7210 · **Posted:** Mon Aug 02, 2010 3:14 pm

dgeist wrote:

BlackLibertyCRD wrote:

Getting low on freon is another reason it could ice up. Adding a can of freon should cure it.

..or 134a (was the KJ ever made with freon?). I wouldn't be surprised if it's lost a little, it's been untouched for more than 5 years.

I did not know that 1,1,1,2-tetrafluoroethane (R-134a) was not considered a Freon.
Learn something new everyday. :wink:

BlackLibertyCRD · **Posted:** Mon Aug 02, 2010 7:24 pm

dgeist wrote:

BlackLibertyCRD wrote:

Getting low on freon is another reason it could ice up. Adding a can of freon should cure it.

..or 134a (was the KJ ever made with freon?). I wouldn't be surprised if it's lost a little, it's been untouched for more than 5 years.

Hey, I'm an old fart from the old school of hard knocks, I still call it freon. :goink:

dgeist · **Posted:** Fri Aug 06, 2010 9:34 am

flash7210 wrote:

I did not know that 1,1,1,2-tetrafluoroethane (R-134a) was not considered a Freon.
Learn something new everyday. :wink:

Hmm, I had to go look it up to ensure I was correct. Sure enough, Freon is the trade name for a bunch of the CFC compounds used for refrigerant, propellant, and fire suppression. R134
is an HFC compound. Subtle difference which I'm sure is irrelevant for most folks unless you're getting your AC charged...

http://en.wikipedia.org/wiki/Freon
http://en.wikipedia.org/wiki/HFC-134a

Regardless, I think I need some of the latter. Anyone used one of the auto-parts kits on a CRD? Does it work well and how hard is it?

Dan

BlackLibertyCRD · **Posted:** Fri Aug 06, 2010 12:26 pm

The kit usually is one 12oz can of 134a and a charge hose. Some of the charge hose has a gauge on it so you can get a low pressure reading. Some cans of 134a have dye in it to find small leaks that is spotted with a UV light kit. When your a/c system is low enough to notice, it is at least one can low, sometimes two.

AC behaviour in hot conditions?

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