I live in Florida and found that my 2004 Volvo s80 T5 runs great in the winter time but is a pain in the summer. If the interior gets too warm (sitting in the sun, hot day out, ect.) the car will start to have some issues that pop up after about 5 min of driving.

The full list of symptoms in order of frequency (high to low) is as follows:
"SRS Airbag Service Urgent" message
Headlights clicking
Loud thud sound (as if ABS is malfunctioning)
Dashboard dies (all gauges and lights)
Electronics die (turn signals, A/C only blows hot, power windows, power locks, power seats)
"Brake Failure - Stop Safely" message
Transmission stuck in third gear (slow acceleration)

I work at a Volkswagen and had one of my Techs look at it. He ran the codes and told me that the only issue was "communication with the ECU being interrupted while driving". The Volvo dealership said that it was an issue with my alternator, and an old family friend who is a mechanic said to insulate the wires to the ECU with fiberglass. I really don't know what to do and am trying to not spend too much money.

Keep note: the issues only appear if the car's interior is above approx 90-100 degrees, under heavy rain, or if i am driving for a long (over 2 hrs) trip on a hot day. also, i have the SRS airbag issue constantly, as well as a bulb failure light, but that i believe i can fix by changing the bulb.

when everything dies, i can drive, in third gear, and stop safely, just don't know how fast i am going, rpm, how much fuel, etc. any help on this issue would be great. thanks

 

My alternator went out recently in my 2009 - and right before it happened I had the same issues as you have except for it didn't matter warm or cold, wet or dry -

 

i would first check the voltage on the battery when fault lights com up if possible(wile car is running). ...if any volt reading is below 14v maybe a number of things if alternator is NEW(EXACT SAME ISSUE AFTER RAIN)....Also check the battery voltage when when the car has been sitting for a few hours...again any voltage below 12v means BATTERY it will cause minor electrical problem in my experience......p.s my srs light has been on since day one....new battery and refefb alternator, first six months of owner ship ..3 years later , now am having a whole heep of electrical problems......ABS and lights galore...............................

READERS BEWARE IF YOU DARE READ MY ABSLIGHTS,IGNITION SWITCH,COOLING FAN, ALL REPAIR POST

GET A POT OF COFFEE BREWING AND A FULL PACk OF CIGARETS.....LOLOLOLOOL .....and yes i am in love with my t6!!!!!

 

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