# HASCO HAT901CSDC12 - Intrigued????



## 102172 (Dec 22, 2006)

The plot thickens.....

You'll recall that a few weeks ago, the day before setting off for a race meeting, the water heater in my RV wouldn't work. Mad panic and Dunc managed to help me jump start the heater. It is still jury rigged as I haven't had time to investigate the HR control system yet.

Well, I'm off racing this weekend and whilst cleaning the sink my wife said "why does the water pump keep switching itself off?". Oh balls. The water pump system is on the fritz. Sure enough, a few seconds after pressing the touch switch for the water pump (touch on/touch off) the light would go out and the pump would stop. This is almost the same problem I am having with the water heater which is switched on in the same way - with a touch switch. Hmmmmm.

I traced the problem with the water pump to a relay. Very odd it is too! Or is it - perhaps this is a standard RV arrangement:

The relay has the traditional high current contacts which are joined together by a coil activated switch. However, this coil has three wires. A live an earth and a switch. When you press the momentary push switch what happens is you connect the switching wire to earth. When you release the button the contacts are made and the relay then applies 12v to the switching wire which feeds back up the wire to the push switch and illuminates the LED. Press it again and you once more earth the switch wire which brakes the contacts and turns the relay and pump off. 

I think the relay is bust as it holds for a while and then drops out. Giving it a clout makes it hold for a little longer but it drops out eventually. I'm fairly sure that it is knackered. Especially as when investigating the water heater fault I became suspicious of a black box between the push switch and the heater itself. Some more investigation tonight has revealed that that black box is the same part as the water pump one. They are both HASCO HAT901CSDC12. 

Any thoughts?

Also, any idea where I can get a couple of these? A net search only reveals suppliers in the US. Are they sufficiently common in RVs that someone in the UK might keep them? Linda, any ideas?

Anyone else had similar experiences?

The only saving grace is that this water pump fault may have helped me diagnose the heater fault too!!! Hooray if it has but no chickens being counted yet!

I currently have a switch connected across the relay so I can work it this weekend, so I'll have to go outside to turn the chuffin pump on - bugger.

Also, my time in the frozen north is ticking away now. Auntie Liz will probably be moving me back to the south in the next 6 months, so I might be able to make it along to a few rallies. If anyone happens to be at Cadwell Park race circuit this weekend feel free to pop over for a brew.

Cheers.

Paul


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## damondunc (Feb 14, 2006)

*hasco relays*

Hi Paul,

try this one

www.tech-rep.co.uk

look under electromechanical relays and you will find they are agents for hasco, look under 900 series.
Dunc.


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## 88927 (May 10, 2005)

Hi Paul
Any joy with this yet matey? Hopefully you will report that both of your faults are now clear :lol: :lol: :lol: 

Keith


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## gromett (May 9, 2005)

Have you tried cleaning the relay contacts?
If it is a double gang relay you may find that you have a momentary action switch. the second set of contact on the relay are then wired to break the contacts on the second push. If this is the case, take the cover off the relay and use a very fine emery board on the contacts then a little WD40.

If it is not a double gang relay. Have you tried putting a voltmeter across the coil contacts and checking if the 12v is removed when the relay disengages. It will help rule out a relay fault.

Karl


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## 102172 (Dec 22, 2006)

Dunc,

Many thanks for that. I've been away for a few days (racing at Cadwell, had another blown tyre on the RV - the remaining US ones will be changed before the next outing!) and just picked this up. I'll be ordering a pair asap.

Keith,

Not yet fixed, but it better be soon. It's starting to annoy me having things not working properly. 

Karl,

Thanks for the tip, but unfortunately the relay is potted so it is impossible to take apart. Also, I have no idea how the self latching mechanism works but it seems to be a very odd arrangement: apply earth, relay makes and 12v sent back up the wire you have just earthed; earth that wire again and relay opens. I'm pretty sure it is a duff relay.

Cheers.

Paul


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