Towbar Relay

[Mildu]

Hi

I've a PCT towbar and universal electrics fitted to my car.

I'm not sure if I've a problem with the relay for fridge, battery, power - the problem is the fridge doesn't seem to be getting as cold as it should.

A friend said the relay might not be powerful enough and a 30amp relay was need not a 20amp.

I've not been able to find on the internet what rating the relay fitted to my car is and it doesn't say on it. I'm not sure where it was fitted (the garage where I bought the car from subcontracted the work).

The relay is a PCT Automotive Volton Combi - part no. ZR1220. Any ideas what this relay is rated at?

Before I set about changing parts or incurring costs any information would be appreciated.

Many thanks

 

[birdman101]

I have just googled the fitting instructions and it says supply via a 16 amp fuse.
What size cable has been used you may have voltage drop if it is to small

 

[Tony_374371542]

Are you expecting too much from the car/fridge system?

As far as I know, the 12 volt car system is designed to keep the fridge cold after it has been cooled by either the gas supply or mains.

 

[ProfJohnL]

Hello Tony
"As far as I know, the 12 volt car system is designed to keep the fridge cold after it has been cooled by either the gas supply or mains."

That may be true for sone designs, but most caravan fridges don't actualy mind which power source is used, as they all use roughly the same amount of power. with 12V the relatively high current would flatten a battery quite quickly so this is only normally available when the engine is running.

Its more a question of convenience and practicality. Before starting a journey it would be inconvenient and massively expensive to have to run the car to simply cool down the fridge, using gas means you will have less for your holiday, and it is certainly the most conveient to use mains 230V from the EHU.

When Driving, I don't think anyone has a longe enough EHU to keep the fridge running on mains

, and it is unsafe to run it on gas (the gas shoudl be turned off whilst traveling), so that leaves 12Vdc from the cars alternator.

Of course on site if you have an ehu then mains is the best option, but if you dont have a pitch with an ehu you can use gas.

 

[colin-yorkshire1]

hi Mildu.
the 12v wire to the fridge is direct linked to the caravan plug via pin 10 "13 pin plug" or pin 6 "on the old grey 12s plug" it will not take power from either the vans lesiure battery or the car battery unless the engine is running via the smart relay.

I don't thnk the relay is likely to be the problem, you can test the output voltage from the socket pin10 on a 13 pin socket or pin6 on 7 pin 12s ,(the fridge wire) and with the engine running if the voltage is 13.4ish changing the relay will be of no use. it is the time scale of the tow that is the determining factor most of us tow to a site within 4 hours and stop in between as soon as the car stops the power is cut to the fridge, so no further cooling is possible untill the car is started and back on tow, even on a longish tow 6 or 7 hrs in total will not cool the fridge down to running temperature on it's own and the reason most of us pre-cool the fridge on gas or EHU at home for 24hrs before departing,

ps, note for the Prof "When Driving, I don't think anyone has a longe enough EHU to keep the fridge running on mains

, and there was I thinking you had no sense of humour,

colin

 

[Mildu]

Hi Guys
Thanks for your responses and sorry for not posting sooner - young family been keeping me busy!
I found the fitting instructions for both the relays on the Internet and checked the car wiring - everything seems to have been done correctly. The relays take their power supply from the 'rear electrical centre?!' I don't know what size of wires have been used but the wire to the 'charging' relay is thicker than the wire to the 'road lights' relay. The charging relay has a 20amp fuse and the road light relay has a 10amp fuse. I've used a circuit tester to confirm there is power going to & from the charging relay - which switches on & off with the engine as per the fitting instructions.
I'll see how things go for while - there's a branch of Indespension not too far way where I might take it to get things checked over.
Thanks again for your posts.
All the best