This is a good idea to use IPA. In rare cases, I have seen piston decoupling issues (although, not on an agilent) but the issue was resolved by using high flow rate of 5ml/min IPA for 20 minutes on each line. remove column, just run pump out to waste at 5 ml/min.
Were the new seals worn-in with IPA at 350 bar minimum?
If your using buffers, be sure to rinse with water as seal wash.
Changing the autosampler parts should have no impact on pump pressure
Is your pressure fluctuation cyclical?
im not too concerned about the voltage, if you had a 24V power supply issue, it would be obvious.
normally I tackle pressure issues in this order:
check valves (OBV)
pump seals
AIV cartridge, AIV
usually mcgv is bad when new seals wont resolve retention time shift issues
rare cases: new pump head, deagsser
You can also remove the pump head and turn on pump and watch the pistons move and compare visually if there is an irregular pattern at different flow rates
Consumer Products Guy wrote:
Let's take a different approach after that if pressure still fluctuating.
Put the same solvent like IPA or a pre-mixed solvent in all four reservoirs. Purge all four lines at least 10 minutes at 5ml/min. If there are no pressure fluctuations doing this then the pump head itself is OK, then suspect the multi-channel mixing valve.
Obviously, check for leaks, even at the outlet of the purge valve and up underneath the pump head itself (use a mirror).