Thread: HEVAC Issues

mmm mate,, thats a werd one,, i havent herd of that prob before with the p38,, an we havent had eny cars come in with that prob,, alltho it dosent get that hot round here, i would suspect LR would no bout it as there are alot of places around the world that get that hot, if enything id look for a SSM or TB on it???

i think it would just be a update yes

Your symptoms have not occurred with me either, my aircon works in +40 degrees no problem. Its an odd number to have programmed into the firware as well. I would think the problem is something else, perhaps the air temp sensor?

Hi Ron - did the "little book" symbol display on the HEVAC when the problem occurred?

My previous P38A, which I believe was made with a month or two of yours, never switched to heat on a hot day but did occassionally just blow ambient air. It was almost always accompanied by the book symbol on the HEVAC.

The bad news is that it went away when I had the blend motors replaced early last year.

My "new" P38A was doing that today too. Even setting the temp to "LO" and manually setting the fans to max there was just a trickle of ambient air blowing through. And yes, I also have the little book symbol on the HEVAC.

Please no, not blend motors again...

No chequebook symbols. It was fine once the temp dropped.

See also RANGE ROVER HVAC DISPLAY ECU

Blowing hot air on very hot days is software fault in early versions of this ECU. I suspect that the software engineer did not 'cap' the temperature tables so above about 45C the software wraps around to lowest temperature in the table but email if you know better. Not much fun in Arizona. Fault can be alleviated by keeping vehicle internal temperature below threshold when parked - park in shade or cover sun exposed windows with alloy foil.

Ron, do you know the part # of your HEVAC unit?
Hopefully you have JFC102540.
There were quite a few supercessions of this part for various anomalies in the AC system & the latest part number seemed to fix most of them.

Mine drops the compressor out for 5min or so at times for some strange reason (it has the compressor relay & harness mod).

No, I don't know the part no. of the panel. I'll pull it out and check. Dunno if it was ever replaced under warranty.

Note how the problems are not electrical faults per se but software design issues.

So resurrecting this thread... any solutions as this issue of Rons (or Pauls if same issue) has been ongoing for a couple years in my dads p38 and time to get it sorted.

Does anything show on the computers if plugged in as yes we get the book/warning symbol come on when blowing hot air. Hasn't been fun over summer.

I haven't had the problem recur but I have made another change.

You need to check the gap between the clutch and the compressor. Also has the car had the air-conditioning link harness modification?

If you click on this link RangeRovers.net • View topic - A/C Clutch Harness Recall? you can see about the modification and also how I machined the clutch to reduce the air gap.

It could be worthwhile doing both of these.