300tdi blower only working intermittently?

Hi all.

Merry Christmas you lot.

I have a '95 300tdi and recently replaced the alternator and sorted the cooling system after a few busted bearings and a shredded belt.

All working fine now to drive but since she's back, the blower on the heater is only working intermittently (sometimes good when going up or downhill or I've braked hard or hit a bump.

I've checked the pipes to heater and seems to work fine. I've done my best to wriggle along the wires to see if connection but can't get a result.

All I can think is it's either a fault with when I connected new alternator. Perhaps not generating right amount? Or it's the wiring and I haven't found yet

Any thoughts or pointers appreciated.

IME, the blower switch can be a bit iffy - give it a good waggle about, and/or try some contact cleaner in it.

+1 on the switch.
Also, is the heater box full of water? Intermittent operation linked to going down/up hill might be due to water sloshing around. Take intake cover off and get your arm down the duct pipe. The birds mouth valve drains it, but often clogs up.

Hmm okay. I'll give it a go. You got any photos or links to people having done it to point me in right direction?

Or shall I just dig through manual and see what I find.

It's very straightforward. All you need is smallish cross head screwdriver.
In this picture

The air intake to the heater is the black grille the socket wrench is sat on. It is screwed on to the wing with about 7 small screws. Take the screws out and the black cover just lifts off. If you look carefully, behind the washer bottle, you can see a black plastic duct pipe. This connects the intake hole in the wing to the heater box. The air intake conveniently faces skywards and so rain falls straight in to it. There is a 'birdsmouth' valve, in the bottom of the duct pipe, to let the water out. However, this silts up and blocks. Water can then collect in the duct pipe and get quite deep and enter the heater box which houses the motor. If you are slim, like me, you can get your arm down the inlet hole in the wing to clean it out.
Or, before that, you could squeeze your arm behind the water bottle to find the birdsmouth valve. It's a rubber valve you can squeeze and this lets out any trapped water. If it has clogged with dirt/mud, then you could take off the grille as described, get your arm in and clean it out.
Either way, it's either a 4 minute or possibly extending to a 10 minute job if a quick clean inside is needed.
Hope this helps.

Hey lads,
Checked this and unfortunately no joy. No blockage and intake fan is spinning fine with engine on.

It must be a faulty electronic connection. Unfortunately i don't really have the knowledge to find the problem. Have tried waggling the connections from heater and along dash and in relay box with engine on to see if it does anything but no joy yet.

If you unplug the wiring loom to the heater unit you can use a multimeter to see if your getting steady current to the motor. Theres a purple wire and two green (if it's the same as a 200tdi). You can use a battery to test it. Purple is live and the green wires are the earths for the different speed settings. Sounds like the switch like peeps have said. Might be worth checking the fuse just in case its loose. It's not a difficult job to get at the switch, just need to unscrew the instrument binicle. Replacement switches are expensive but easy to swap over.