Heater only works on full.

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Theantony
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Heater only works on full.

Post by Theantony »

My heater blower only works on full, so I changed the resister I think that’s what it’s called and it still didn’t work. Any ideas what the issue could be. Could it be the relay? Im stuck now.
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tschultz
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Re: Heater only works on full.

Post by tschultz »

What year? Is your heater valve to the heater core bad?
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Theantony
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Re: Heater only works on full.

Post by Theantony »

82 euro auto. The heat is good,
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Soperman
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Re: Heater only works on full.

Post by Soperman »

There is a wealth of information on this site about this very common problem.
Here is a source that I used to fix mine.

https://bigcoupe.com/phpBB2/viewtopic.p ... ls#p237607

Scroll down to Normgrills.net Technical Library. Open that, then look at pages 159-161.

I used them to diagnose my problem. In my case I needed a replacement heater blower control unit (basically the little box immediately behind your fan speed rotary adjuster)
I couldn't find one anywhere, so followed the Normgrill instructions, opened up the unit, had a blown resisiter changed, and it has worked perfectly foe several years now.

Good luck.
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sansouci
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Re: Heater only works on full.

Post by sansouci »

Per Digikey's website, the 2n3551 is obsolete and they only have about 50 of the substitute which is no longer manufactured. It's 2N5301 and it's about $6.i may buy a few.
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Theantony
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Re: Heater only works on full.

Post by Theantony »

Great thanks, I wondered where the norm grills info got to as the link is down, brilliant site used it loads in the past.

I have taken the dash out before for something else so will have a look. I have a couple of those resisters. Thanks.
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Theantony
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Re: Heater only works on full.

Post by Theantony »

It was indeed the transistor on the rear of the switch. Changed and now working 🤞.
Thanks all.
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