Problem with AC temp probe on 2008 330
Having trouble with my Marine Aire with Passport control system. Thermostat does not seem to keep up with the actual temperature. I’ve noticed since last year (my 1st with boat) that the temp shown on the control was usually several degrees lower than temp on a new CO monitor I bought. I calibrated the Passport to the monitor according to manual this past weekend. But problem still persists.
It was rainy Saturday morning so I did a test. Temp in cabin was 79 according to Passport (and CO monitor) and I then set it to 75. Air came on and cabin quickly cooled. After awhile Passport read 78, CO monitor (6’ away and at same height) read 74 and a third thermometer (that was usually within a degree or 2 of CO monitor) that I located on step directly in front of the return air duct was 68. The CO monitor and 3rd one read about how it felt.
What lead to this test was that the night before was a particularly warm night (for northern NY) and we had 6 people stay overnight. The air would run a long time and make it quite cool (almost too much) before shutting off) and then stay off till it was way too hot before kicking back on. The whole night went like that. That's about how my above experiment ran.
From reading posts on this site, it sounds like either temp probe is in bad location or is shot and needs to be replaced.
Looking at back of Passport there is a flat wire with telephone type plug in back of it. That’s how temp probe has been described. If I unplug it, passport goes blank, as if unplugged. I expected wire to lead to temp probe located just behind inlet grill at base of v berth. It was not there. I eventually found this wire connected directly to the AC unit under forward compartment of v-berth. It entered into the top of a metal boxed in area on left side of unit (above the "R" in Danger in the photo). But coming out of the box just to the right of it was another wire, about half the width of this cable and that lead to the probe, attached to bottom of intake to AC unit itself (2nd photo)
I wanted to relocate probe to behind intake grill (near where I had 3rd thermometer placed), thinking it would give a more accurate, real time reading. Probe cable was too short, so only got a 3rd of the way there. Ran the AC but it made no difference.
Seems to me I may need new probe. If so, here’s my problem. I don’t see any way to get into this metal box to attach new probe. Box appears to be riveted together, not screwed. (see 3rd photo)
I’d appreciate any thoughts or ideas. From reading older posts on here this sounded like an easy fix. What am I missing?