Fridge not working on 12v, PC-100/DS-304SR controller problem.

[Widge]

Hi,

I have a problem with the fridge not working on 12v, the fridge works fine the problem is with the DS-304-SR controller (connected to a PC-100 control panel) it looks like the relay is not switching when the ignition is on, on the controller board are 2 spade connectors to allow you to bypass the relay by inserting a link between them, as a temporary measure i have connected a relay to these powered off the ignition.

I have the manual that covers the PC-100/200 controller, but it doesn't have a circuit diagram so without taking the controller board out it is difficult to establish which relay it is.

I was wondering if anyone had a circuit diagram or knew which relay it might be?

I suspect it is the one between the top two connectors (on the picture) as the bypass connectors are on the top and bottom.

Any suggestions welcome

 

[autorouter]

I'm sure you're right about that relay, it's a power relay sitting between the two spade terminal contacts. The fridge 12V power goes to a couple of pins on that 6-way connector to the right, so it's very close too.

You can tell if the relay is working by looking at the voltage between those two terminals with a multimeter. The voltage should be about +12V when the engine is stopped, and drop to about zero when the engine is running. If it stays at zero all the time, it's probably stuck closed. If it's +12V all the time, it's probably stuck open. Or it could be that the trigger voltage for the relay (D+) is not reaching the relay.

Do other things like the split charge relay, maybe awning light cutoff etc work correctly when the engine starts?

If it's a faulty relay, Apuljack Electronics do repairs for that type of unit.

 

[Widge]

Hi thanks for the reply, as i said i have now connected a standard car relay between the spade connectors, powered by the ignition, effectively bypassing the relay, but would prefer to fix it properly, fixing it myself isn't too much problem if i have the parts as i worked in the electronics and computer industry, but as it looks like a pain in the ass to remove i would prefer to diagnose in situe if possible before getting any parts, so it only has to be removed once.

A good tip on the ouside light, i will check that.

Just a side comment, i started the diagnostics by getting the fridge out, (it needed good clean behind anyway), unfortunately the cable for the gas ignition pulled out of its connector and shorted blowing its fuse.

In its self not a major issue, but what was very worrying was at the same time the pump going flat out and the sound of water pouring out under the van, i shut the pump off and luckily i didn't have too much water anyway.

I have since discovered the fuse for the fridge igniter also powers the emergency drain on the waterheater, but I admit i was worried for a while.

 

[autorouter]

You could check if the D+ signal is reaching the relay. There's a diode and resistor (R25 and D6) that are very close to the relay. Very likely the diode is the snubber, that absorbs the reverse voltage spike from the relay coil when the D+ signal disconnects. So the D+ signal should be present across the diode. If the D+ signal is good, but the relay doesn't respond, then at least you know it's faulty.

I have since discovered the fuse for the fridge igniter also powers the emergency drain on the waterheater, but I admit i was worried for a while.

There are a few bits like that, they all go off when that fuse blows, they are unrelated except that they all need a very small amount of permanent power, that stays on when the main habitation power switch is turned off.