How to test a G3B solenoid coil with multimeter

Kealyboy

hi I have a Riello G3B burner that is playing up . I suspect that the solenoid coil may be faulty. The solenoid coil is the one with 3 wires. How do I test this with a multimeter? What resistance am I looking for between wires? Thank you

John.G

My Riello G5X Burner oil solenoid has a resistanc of 1.4ohms between black & blue and 1450ohms between brown & blue.

Kealyboy

thank you very much john

John.G

Here is a photo of the control box terminals, be sure to slacken the screw at the side of the control box, then pull the box back and lift very slightly to remove it.

Kealyboy

thanks John can I test the solenoid while the wires are connected to the control box or should I disconnect the wires and test? Could I pick up stray resistance if connected to the control box when checking resistance

John.G

I think you shouldn't have to disconnect anywhere, 1 to 2 should give 1450ohms and 8 to 2, 1.4ohms.

Wearb

I don't know about other guys, but I don't think I've come across a damaged coil without some physical sign of damage. A coil fault is rare enough in any case.

John's figures do allow for a good bit of flexibility. I.E. don't condemn it if it doesn't read those exact figures.

Kealyboy

boiler fires and runs everything is fine for say about an hour everything hot. Then about after an hour rads are getting cold. go out to boiler motor fan running continuously but does not fire up again. Motor is giving out 50 V AC to control box. I’m suspecting it’s a faulty coil photocell or control box.

Kealyboy

if I turn off boiler and turn back on again, it will fire up intermittently. does not lock out.
it’s like once it reaches temp and cuts out it attempts to fire up when there is a call for heat but motor runs but does not spark or lock out.
I put a old spare coil, control box and photocell in and problem still exists. Motor is giving 50v to control box so can’t be motor.

Has to be the oil pump at fault!! Although washing pressure is evident as ram activates and damper lifts.

declan b

when the issue happens again. Turn off power,remove photocell from control box.refit control box without photocell and restart burner. if the burner fires for 5 seconds and then goes to lockout,the fault is the photocell

jimf

more likely photo cell is going tits up when hot than the coil

do as declan says above

10-10-20

The support and knowledge on here is epic some times. 👍️

Kealyboy

it’s funny when I replaced all 3 parts individually the problem seem to still exist but when I replaced the control box and photocell (old spare ones) together everything seems to be working fine now.

John.G

Maybe tempting fate, but you could try the new photo cell in the old control box.