Braemar TH5, giving code Error 4 Heat shuts off and starts again when it cooled down

Check the fan pressure switch tube. Fixed one today where the tube was cracked.

Originally Posted by plum

Check the fan pressure switch tube. Fixed one today where the tube was cracked.

I was checking the fan pressure switch and tube, nothing wrong.
Double checking everything again, whiched the unit back on, now it's not powering up.
found some corrosion on the main ic.
the control is not communicating with the main heater now.
when u power the heater up, you can hear the relay flicking on and off.
Cleaned off the corrosion from the ic.
Tried resetting the control and the main board but no luck.

can we replace just the ic or do we need to replace the whole board??

pretty sure the whole board unless you've got some electronic experience and can source the part.

Thanks mate, I am trying to source some parts at the moment.
but I haven't solve the problem of the heat switching off, maybe the new board might fix it.
would you happen to know if nest thermostat will work on this Braemar unit?
running the 24 V manual thermostat line?
regards ken

not sure

Originally Posted by Kheang

...
found some corrosion on the main ic.
...

can we replace just the ic or do we need to replace the whole board??

Some of the pins there do look a bit dodgy. Perhaps you could check for continuity from where the pins emerge from the plastic package to the solder on the socket pins (on the other side of the board) and also check that whatever crud has built up is not shorting adjacent pins. Make sure the power is off if you do that.

The IC is an 87C521 microcontroller. I doubt Braemar would supply one, but you could always ask. The IC socket might need to be replaced as well, but no problem getting one of those.

It is a very old type of microcontroller and has probably not been produced for years but I did see some for sale on Ebay as "vintage" items. The trouble is, you can't just buy one and plug it in, because the controlling program needs to be loaded into it.

Originally Posted by Kheang

Hi everyone, i install this heater about 8 years ago, been working fine for 2 years then a had a error 4 then the heater will lock out, worked out that it was cause by the condensate drain assembly which didn't flow.
Now i have the same error code 4, the heater will run for a while, then the heat will shut off, after it cools a little it will kick in again.
The Duct thermistor was install about 1.5 meters away for the heater where the dust splits, i looked though the trouble shoot manual, it said to put the thermistor about 3m away from heater, so i pulled the cable into the duct and placed it about 3m away from the heater, but still giving me error 4.
All out let is fine and fan speed is to the max 10
Any glues to help me fix the problem??

thanks and advance
regards Ken

Error code 4 = overheating signal from the thermistor? Quite often the thermistor is the problem rather than overheating. This happens when rats chew through the wires. I'd pull out the thermistor to see if it is damaged and replace it to see if it will fix the error code 4 problem. You might have other problems as well though.

hi guys, i got the whole kits replaced because the board was to hard to get fixed up, no one replace the old type of board. i install the new board, work fine again but with error code 4 again, replace thermistor, and now it works perfectly.
One more problem, the new board wiring is different to the zone board, might need to get a replacement for that too ? or can it be rewired ?

regards Ken