Under Bonnet 4 Pin Relays on Motorhome - Type A or B?

[StitchUp]

Our fridge only seems to work on gas! I understand that it will only work on 12v when the engine is running and providing enough power.

Reading a few of the posts on this forum I understand the problem might lay with one of the relays located under the bonnet to the left of the battery (Fiat Ducato). I've removed the two relays and any legend that used to be on them has disappeared.

Does anyone know whether these relays are Type A or B?

I believe the 2nd relay might be for split charging.

The motorhome is a Lunar Roadstar 720 year 2000.

Thanks

 

[Bessy765]

Might be an idea to put the relays back, then check at the fridge there will be two supplies 12 volt on most fridges depending on age and type of fridge. With the relays back in does your fridge have an internal light does it work, is there an igniter that clicks when you light it. If so the low amperage 12 volt is ok. You then need a heavier 12 volt supply this is a separate thicker wires. Most modern fridges need a signal from the D+ (alternator when it starts charging to close the relay and supply 12 volts to the fridge whilst the engine is running. The make ad model of your motorhome and. Fridge will help in identifying the problem. Be aware the the 12 volt from the engine is not a great source for cooling the fridge it will just about hold it at whatever temp it was before you started the engine.

 

[Itsmcb]

I have these two different ones, sorry I can't remember which is the fridge one.

 

[Itsmcb]

There should also be a small fuse box near the relays. One of these will supply the power to the fridge relay.

 

[pappajohn]

Type A..... NO (Normally OPEN) closes when engine running

Type B....NC (Normally closed) opens when engine running.

You need Type A

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[StitchUp]

Thanks for the quick replies

When the fridge an Electrolux Electrolux RM6505 AES is switched on there are two fairly loud 'clunks' and then the LED flashes red - this happens on all but the gas - even when on hook-up!

The relays are both the 4 pin type so I guess 2nd in the picture above reply from Itsmcb I've removed all the fuses and checked them - fuses are okay but not so sure about the contacts in the holders. They are located in a difficult place to work!

 

[pappajohn]

If the two relays are easily accessible swap them over.... If the fridge works its a faulty relay.
It may be getting power for the electronics (low amperage) direct from the leisure battery but the relay is preventing cooling power (high amps via relay) from the engine battery

 

[StitchUp]

Already removed the relays and now ordered replacements - thanks for the advice.

Relays

 

[mitzimad]

playing parts darts can get very expensive better to test with a meter first to see whats failing

 

[autorouter]

Does anyone know whether these relays are Type A or B?

Type A and Type B refers to the terminal layout. For a 4-pin relay, two pins are the coil (85 and 86, low current) and two pins are the main contacts (30 and 87, high current).

The pin layout in Itsmcb's post is type B. The low current pins are left and right, the high current pins are top and bottom. If you look at the relay sockets in your picture, you will see two thin wires left and right (low current) and two thick wires front and back (high current). So your relays are Type B.

Type A terminal layout has two coil pins next to each other, and two main contact pins next to each other, not opposite.

Both NO (Normally Open) and NC (Normally Closed) relays are available in either Type A or Type B. For your applications - split charge relay and fridge relay - you need the NO type, which is the most widely available anyway.

More info here. Type A and B is shown, scroll down to it.

Automotive Relay Guide | 12 Volt Planet

Read our guide to relays found in vehicle electrical systems. How they work, why they're used and some example applications

www.12voltplanet.co.uk

Edit: I think the two new relays you ordered are the right ones - Normally Open Type B.

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[StitchUp]

Quick Update:
Took the relays to work and tested them - one was good, the other faulty.