fortgrange · Feb 20, 2012

2002 P38. Did a 200 mile return journey to Loughborough at the weekend. On the way home outside temp dropped to 1 degree, climate set at 24 degrees both sides, started feeling chilly so turned up the heat in 1 degree stages with no noticeable difference, got to 28 degrees still not much more than luke warm, went up to high and suddenly its Silly hot, way too warm so back down to 28 and luke warm again, back to high and unbearable again.

Going up through the temps I was thinking the blend motor was sticking but the fact it would go from luke warm to very hot every time I switched between 28 and high made me think this wasn't the case as going down the temps it should be more gradual (even if it is sticking), shouldn't it?

Apart from renewing the blends on the last P38 I've never really researched how the climate control actually works, so maybe some internet trawling is required.

In the mean time if any of you good folk have an opinion please feel free to enlighten me.

I should also point out that there were no hold ups so we had maintained a constant speed of 70/80 mph and as soon as we got back on to normal A roads the climate control behaved just like its supposed to, don't know if that makes any difference.

Datatek · Feb 20, 2012

Cabin temperature sensor blocked with fluff or the heater matrix temperature sensor failed, need to put it on diagnostics to know for sure.

rewmer · Feb 20, 2012

My moneys on the cabin temp sensor. Stick a pin or similar in the grill to see if the fans spinning.

egor8384 · Feb 20, 2012

Datatek said:
Cabin temperature sensor blocked with fluff or the heater matrix temperature sensor failed, need to put it on diagnostics to know for sure.

Would that cause the cheque book to show up?

jerrytlr · Feb 21, 2012

Had a similar problem with mine, diagnosed using Data's Faultmate as heater core temp sensor - I have only just got around to putting a new one on, and now it seems to work fine! Very easy job by the way.

Cabin temp sensor another def possibility, and as you say it is unlikely to be the blend motors as the system is still capable of going from full cold to full hot.

You really do need to get it onto diagnostics, ideally one that can read the temp sensor values so you can see if they are saying something sensible....

BTW my core temp sensor problem was intermittent, sometimes it worked OK sometimes it didn't, and it did also sometimes throw up the cheque book symbol

HTH

Cheers

Jerry

kds · Feb 21, 2012

I go with rewmer check the cabin temp sensor (little grill under clock), had just same thing on my p38 when the little fan stopped working.

Henrik97 · Feb 21, 2012

fortgrange said:
2002 P38. Did a 200 mile return journey to Loughborough at the weekend. On the way home outside temp dropped to 1 degree, climate set at 24 degrees both sides, started feeling chilly so turned up the heat in 1 degree stages with no noticeable difference, got to 28 degrees still not much more than luke warm, went up to high and suddenly its Silly hot, way too warm so back down to 28 and luke warm again, back to high and unbearable again.

Going up through the temps I was thinking the blend motor was sticking but the fact it would go from luke warm to very hot every time I switched between 28 and high made me think this wasn't the case as going down the temps it should be more gradual (even if it is sticking), shouldn't it?

Apart from renewing the blends on the last P38 I've never really researched how the climate control actually works, so maybe some internet trawling is required.

In the mean time if any of you good folk have an opinion please feel free to enlighten me.

I should also point out that there were no hold ups so we had maintained a constant speed of 70/80 mph and as soon as we got back on to normal A roads the climate control behaved just like its supposed to, don't know if that makes any difference.

Mine is behaving very similarly, so I'd be very interested to know what you find out. Usually the malfunction is accompanied by outside temperature display totally out of whack, like showing -40C when it's actually +5. Like yours, it's intermittent and sometimes works perfectly. It will usually stabilise after a drive of 30 minutes and then stay ok fro the rest of the journey. Keep us posted!

H.

fortgrange · Feb 21, 2012

Thanks one and all for the suggestions. Heading for Norway at midnight tonight so the only thing I can really check before we head off is the cabin temp sensor. At least it still gets to hot if we do hit some really cold weather. Diagnostics will have to wait until we're home.

I have no book symbol and on our last P38 the last time the book symbol appeared it was diagnosed as heater core temp sensor although every thing was working fine. Changed it any way and book symbol disappeared but the climate control did not become any more efficient!!

jerrytlr · Feb 21, 2012

Just checked my cabin sensor this afternoon, as I think it is reading too high (checked using Nanocom). Just shine a torch into it; you can see the fan spinning and also if there is a lot of fluff in there. Mine is almost totally clear of fluff and fan spins nicely, so not sure why it is overreading...

Cheers,

Jerry

fortgrange

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