u/Alternative-Time-836

My blower works fine when set to ON. When I notice a problem with it in AUTO mode, lately I switch it to ON so that I don't have to worry about any malfunctioning.

TLDR;

Blower isn't timing properly with the compressor and sometimes doesn't turn on when the compressor comes on if on AUTO mode. Thermostat was changed from analog to digital before problems started (may or may not be relevant).

More Details:

I read that if the blower is overheating, it will shut off regardless of whether it is on AUTO or ON mode. Is this information correct?

If so, then the malfunctioning of my blower when on AUTO mode must not be attributed to overheating (?) because it works fine in ON mode.

I am encountering three issues (intermittently, but not necessarily daily, though sometimes multiple issues in a short span of time, then back to normal):

The compressor will come on, but the blower will not.
The blower will shut off 5-15 seconds before the compressor or start a handful of seconds after the compressor comes on.
I infrequently hear momentary drops in speed for the blower as it is operating.

I only started noticing these issues within the last couple months, but I don't know how long they have been happening. I assume it's a contributor or perhaps the reason why my lines are freezing.

Three possibly pertinent details:

I do have inconsistent power. The lights flicker or dim pretty often, tv blinks, clocks reset, etc. I live in a tiny rural community with poor infrastructure, which may explain issue #3.
I switched thermostats 1 or 2 years ago from an old one to a "new" one (that wasn't actually "new" but left here by the HVAC tech several years back if we wanted to switch to digital ones, which I put off because I didn't really care). I don't know whether the thermostat could have anything to do with issue #1 or #2 (due to improper installation or a defective device?) - I can switch it back if I can find it if this is a possibility.
I do leave my blower set to ON for 6-12 hours on hot days over the last couple years to keep the lines from freezing once I noticed the problem. (In the past week, I have switched to only leaving it ON for 2-3 hours at a time and then setting it back to AUTO for 3-4 hrs to not overrun it and allow the space to dehumidify before repeating the process until nighttime when I set it back to AUTO, though I've noticed blower issues anytime of day, which has me anxious about having it set to AUTO overnight.)

Main Question:

What can I do on my own without an HVAC tech's assistance to address these problems if anything?

(P.S. I posted yesterday and was incorrect about there being sludge in my condensate pipes; from what I can tell from a photo I took today to actually look inside where it exits the house, the pipe is clear. Still troubleshooting the frozen lines for a differential diagnosis to it being caused by dirty evaporator coils, though I guess the problem could be that my blower is failing, which was the other suggestion.)

Thank you for any insight you can provide.

I've been living in my house for over 8 years. Last spring, I noticed that my pipes were freezing, though I'm uncertain when they started to freeze. I called the HVAC guy in my area, he looked things over, said everything looked fine, but the blower could be failing and to check if it gets hot (it doesn't as far as I can tell), or if that wasn't the problem, the evaporator coils could be dirty and need cleaning, which he said would cost a lot because the entire unit would have to come out, and he seemed to discourage me from considering this (possibly because he's been wanting to retire for years and doesn't want to take on that job).

I spent last summer regularly running the blower/fan through the day or sometimes overnight to try and deal with the freezing lines, which worked fine while it was on, and sometimes I could get a couple days without the lines freezing before needing to do that, depending on the temperature outside or sun intensity. The freezing of the AC lines began again this year as soon as temperatures got to around 90 (it regularly gets to 110-115, sometimes higher, in the summer and humidity is high). I set my fan to ON during the day once I notice the lines starting to frost or be icy to the touch (around 11 or noon currently), but doing this is causing my humidity level to go from about 60 to 72 inside (second floor).

A couple weeks ago, I noticed the condensate pipe outside was disconnected at the join from where it exits the house. I put it back together, but went outside yesterday to look at the angle and adjust while troubleshooting (propping it up so it was no longer sloping upwards from one of the joins). When I did that, the pipe disconnected at the house again, and I noticed sludge along the interior walls of the pipe, which made me wonder if the water from the unit was having trouble draining efficiently because of this. I've never cleaned the condensate line, didn't know it was a requirement until I read this yesterday while researching how to fix the freezing lines.

Water is draining from the pipe, enough that it was causing water-damage where it was draining outside when it was disconnected from the first join, so it isn't fully clogged. I don't know if the condensate pipe condition is the cause of the freezing lines. It wasn't suggested by the HVAC guy last year. I was trying to get him on the phone for the last couple months (but his voicemail is full) to just ask a few diagnostic questions while I try to fix the problem because there are several different issues I've noticed that I'm speculating on as to which (if any) could be causing the lines to freeze (aside from potentially dirty evaporator coils as suggested).

But maybe it's simply the condensate pipe needs to be flushed? It's horizontal and glued in place at most joins, so I need some advice about how to most effectively get hot water and vinegar through it. Thanks for any help you can provide.

Question about Blower ON/AUTO modes and cycling

Freezing lines. How to clean my condensate pipe?