Thermo Top Z/C Not Starting

[Jjgr99]

Hi all

I have a Thermo Top Z/C which has been installed and working fine for the last 5 years. It runs 3 rads and a calorifier. I serviced it last year and replaced the burner unit and has worked perfectly until this week.

 

The heater goes through the normal procedure - Blower fan - water pump but then it hums loudly when the fuel pump would normally start clicking.

 

I have tested the water pump and fuel pump and they both work fine.

 

Not sure what to do next.

 

Any ideas really appreciated.

[mross]

Have you tried the troubleshooting section in the manual? That's the only help I can offer, I'm afraid.

[Flyboy]

Check the voltage at the unit whilst it's starting up. Low voltage is a common problem with failed start up.

[NMEA]

Not sure why you mention the Z, you could not possibly have one on a CH system as they have no provision for a coolant pump, they are for cars as an auxiliary and rely on the car water pump. So, you have a TTC, how did you test the pump? I have come across humming before on a few occasions and it was caused by an ECU failure transmitting a constant current instead of a pulse to the pump, if you check the current at the pump during start up it will confirm if that is so.

[Jjgr99]

Thanks for the replies. I'll check the voltage, but it's a brand new battery with a trickle charger constantly connected.

 

It is a Thermo Top Z from a Rover 75 which were fitted with a circulating pump. I have two of them, one on the boat and one in a caravan. I tested the pump by connecting it to the battery and pumping water, which it did without any problems.

 

I'll try testing the current to the pump and share the results here.

 

Thanks again.

[NMEA]

If there is nothing wrong with the circulation pump then re read my earlier post re the fuel pump, that is where the issue probably lies.

[Jjgr99]

It turns out it was a voltage issue after all. I've gone back to it after a few days charging and it works perfectly.

 

It seems the trickle charger can't charge fast enough for the amount of power the heater needs.

 

Thanks again for all the advice

[MtB]

It turns out it was a voltage issue after all. I've gone back to it after a few days charging and it works perfectly.

 

It seems the trickle charger can't charge fast enough for the amount of power the heater needs.

 

Thanks again for all the advice

 

 

Thanks for reporting how it turned out.

 

This suggests a seriously goosed battery. The Thermotop only draws a high current during start up (in the order of 15a) which even a very poor battery will easily supply. Current drawn will then fall to two or three Amps.

 

I'm guessing you are on a shoreline charger 24/7, yes?

[Jjgr99]

@Mike

 

Yes, it's a 0.5amp trickle charger on shoreline 24/7, but the battery is a starter battery, brand new.

[MtB]

@Mike

 

Yes, it's a 0.5amp trickle charger on shoreline 24/7, but the battery is a starter battery, brand new.

 

 

This (rather odd) setup should be perfectly capable of starting the Thermotop.

 

I suspect the charger isn't actually keeping the battery charged, and the battery is utterly flat.

 

Can you measure the voltage across the battery terminals while the Thermotop is starting up?

 

Or are you saying the problem has now completely gone? If so, I'd say prior to the problem arising the battery was flattened and a few days at 0.5a has woken it up.

[Jimmyzx10r]

Hello I’m wondering if anybody can help me I have a webasto thermotop z/c-d 

the problem I have is the air fan runs at start of operation then that is it just stops no ticking on fuel pump I have put a new fuel pump in as everyone I’ve asked has said it’s the fuel pump but still nothing happening I’ve disconnected fuel pump diesel tube heater side to see if blocked seems ok I then found my multimeter seems to be no voltage to fuel pump at all been told must be ecu but reluctant to buy without seeing if someone else has had similar problems thank you 

[Jen-in-Wellies]

Welcome to the forum.

You only see voltage to the fuel pump momentarily for each pulse of fuel. Chances are you might miss it with a multimeter. What is the actual voltage between 12V and ground at the Webasto when it is trying to start?

[Jimmyzx10r]

Thank you sorry for late reply had to climb back down engine bay takes me a while in my old age I’m getting 12 volts on start up