My volvo v70 heater wont work

It's probably the fan resistor for low speeds that fried.
Here's a video on how to replace it on a Volvo V70.

volvo v70 Don't worry I'm sure you will get the solution of your problem, just check the link I attached
They have all wiring, schematic, and electrical diagrams, instant download.

The A/C needs to be serviced by a certified volvo tech or some one who know's a/c very well it can be just low charge or the speed sensor on the compressor.

Most cars have a feature called a neutral safety switch. This device generally provides two functions: first it prevents the starter from being engaged unless the transmission is in neutral or park gear, secondly it turns the back-up lights on and off as appropriate. With age and use this switch can and does fail and more often it needs adjustment. Being a volvo part I do not imagine it is carried in stock at most parts stores, however a dealer's service/parts guy could show you the part, and its location on an illustrated parts breakdown. He also could give you some idea of how often this part creates problems such as yours. You could then make a decision as to whether or not you want to replace yours and whether or not you want to do it yourself.

1. Check all the necessary fuses.
2. Check there is no obstructions on the air path (from outside to inside).
3. Behind the centre console (behind where the ashtray is) and under the panels is a drain for condensation. use a pipe cleaner to clear any obstruction.

You could try disconnecting the battery for half and hour (worked with mine).

It could ultimately be the ECC module that is dead. New ones are pricey. I got a second hand one from Salvo Group in Notts (UK).

The fuse for heater/ac fan is number 36.30 amp located end of dash
If this is ok,you need to replace heater control module behind heater controls.Save money buy haynes manual,check e bay

check under the filter.. maybe some stuff in there that's slowing down the motor and setting off the slow speed sender unit..or could be bad bearing or brush on motor.
try to move it and listen for scraping or clicking noise - bad bearing...

stuff, as in you would never believe me if I told you.

My volvo v70 has three places for fuses and relays, one under the bonnet, one on the end of the dash board on the drivers side, and one the boot on the left hand side you may find what your looking for in one of these places

Try the fuel injection relay they are located under the hood. They blow out every few years on my Volvo. The car starts to quit all of the sudden. It is either red or green colored. It is located in the fuse box under the hood.

get the codes read,get the throttle body update (free from volvo) done,reset service by holding odometer button done and turn on key till lights come on dash and what approx 5 second release and turn off key ,you may need to do it again until it works