Varkanoid

Hope someone can help me. We had a new conservatory and I disabled and removed the PIR sensor in there. Today the electricians came and wired up the lights etc in the conservatory and they turned the power off.This evening I reconnected a new PIR Sensor in the conservatory went to do a walk test and none of my PIR sensors were working. Checked them and the red led lights are not on.So far I have checked.1. All the fuses in the control panel and the fuse spur underneath all okay. (tested with multimeter)2. Measured the 12v wires on each PIR sensor and they are getting 2.5v (which seems wrong)3. Double checked I have wired the new one up.4. Alarm battery is okay and getting 13.8v replaced new 4 weeks ago.5. Transformer is outputting 20.5v AC6. Traced the 12v green/white wires back to the control panel and measured the voltage from the terminal and it shows 2.5v.I can not remember the last time I saw the PIR sensors flash red but we went out yesterday and set the alarm okay. Now today when I set the alarm the 4 red lights light up for 1-4 sensors but instead of the usual exit beeps I just get 4 beeps repeated. I have now found out this is because the Alarm is detecting the 4 PIR sensors are not available, probably due to no power/low power.So as far as I can tell the 12v aux output terminals from the control panel are outputting 2.5v not 12v ? Does this look like the problem and it needs a new Control Panel ? Is there anything else I can test. Noticed the Control Panel has 2002 on it !Thanks for any help in advance.

Hi in need of help, guess I should go post.