 | Home > Technical > Heated front screen only turns on for a second |
 
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| hank Member Since: 12 Sep 2016 Location: South Wales Posts: 2296   
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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
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5th Apr 2021 2:44pm |
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| diesel_jim Member Since: 13 Oct 2008 Location: hiding Posts: 6092  
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Mine did that.... was the timer relay (bottom of the fusebox had got deep in water and corroded the pins on the timer unit)
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5th Apr 2021 5:07pm |
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| s55shh Member Since: 30 Dec 2019 Location: staffs Posts: 193
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was the engine running? Mine does this if ignition on but engine not
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5th Apr 2021 6:04pm |
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| diesel_jim Member Since: 13 Oct 2008 Location: hiding Posts: 6092
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The relay is connected to the oil pressure switch. oil pressure = engine running, thus alternator charging the battery.
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6th Apr 2021 5:49am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17359
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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.
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6th Apr 2021 8:19am |
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| jimbo55 Member Since: 15 Jul 2020 Location: Midlands Posts: 399
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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
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6th Apr 2021 9:25am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17359
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Yes, if it is aftermarket then anything is possible!
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6th Apr 2021 9:36am |
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| s55shh Member Since: 30 Dec 2019 Location: staffs Posts: 193
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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!
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12th Apr 2021 8:26am |
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| hank Member Since: 12 Sep 2016 Location: South Wales Posts: 2296
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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 |
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13th Apr 2021 11:19am |
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| hank Member Since: 12 Sep 2016 Location: South Wales Posts: 2296
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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 |
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21st Jan 2023 5:39pm |
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