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hank

Member Since: 12 Sep 2016
Location: South Wales
Posts: 2224

2007 Defender 110 Puma 2.4 DCPU Stornoway Grey

Heated front screen only turns on for a second

Been having issues with the HFS for some time. Occasionally it functions properly, other times nothing, today the switch illuminated for a second and then goes out. Obviously something has failed, any thoughts on what? Timer relay maybe? [/u] > 110 XS Double Cab
> Instagram @simonlanemind

5th Apr 2021 3:44pm

jimbo55

Member Since: 15 Jul 2020
Location: Midlands
Posts: 385

Firstly check all of the connections, you may have a loose connection causing it to turn off. Other than that I’d be looking at the timer relay,
I’d have thought almost other things would have caused the fuse to blow.

5th Apr 2021 4:09pm

diesel_jim

Member Since: 13 Oct 2008
Location: hiding
Posts: 6031

Mine did that.... was the timer relay (bottom of the fusebox had got deep in water and corroded the pins on the timer unit)

5th Apr 2021 6:07pm

s55shh

Member Since: 30 Dec 2019
Location: staffs
Posts: 182

was the engine running? Mine does this if ignition on but engine not

5th Apr 2021 7:04pm

diesel_jim

Member Since: 13 Oct 2008
Location: hiding
Posts: 6031

The relay is connected to the oil pressure switch. oil pressure = engine running, thus alternator charging the battery.

6th Apr 2021 6:49am

blackwolf

Member Since: 03 Nov 2009
Location: South West England
Posts: 16857

I think on the Puma that the circuit uses an alternator output (rather than the presence of oil pressure) to determine that the engine is running, although the signal is actually taken form the IPAC. If this signal is absent, the timer relay won't energise.

6th Apr 2021 9:19am

jimbo55

Member Since: 15 Jul 2020
Location: Midlands
Posts: 385

Just to confuse things even more, it could also just take an ignition live (from the cigarette lighter or another point in the dash) if it is an aftermarket addition

6th Apr 2021 10:25am

blackwolf

Member Since: 03 Nov 2009
Location: South West England
Posts: 16857

Yes, if it is aftermarket then anything is possible!

6th Apr 2021 10:36am

s55shh

Member Since: 30 Dec 2019
Location: staffs
Posts: 182

just to confuse things, after fitting a double DIN dash, mine is doing the same now. HFS won't stay on more than a split second!

12th Apr 2021 9:26am

hank

Member Since: 12 Sep 2016
Location: South Wales
Posts: 2224

It's a factory installed system.

Mine seems to have fixed itself for the time being... Thinking it might be a sticky contact in the timer relay or something. Will keep my eyes peeled for a replacement

> 110 XS Double Cab
> Instagram @simonlanemind

13th Apr 2021 12:19pm

hank

Member Since: 12 Sep 2016
Location: South Wales
Posts: 2224

Finally fixed this

One of the solder joints between a pin and the PCB on timer relay PRC6796 had cracked.
Reflowed the solder joint and all back up and running

> 110 XS Double Cab
> Instagram @simonlanemind

21st Jan 2023 6:39pm

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