pantera928

My A/C and ventilation unit appeared to be normal and then suddenly. the vent fan would only come on at highest speed and only with the slider switch in the far right defrost position. I can hear things click if i move it to other positions but nothing changes and the vent fan shuts down. Any ideas?
Thanks

SQLGuy

Looks like the defrost position powers the blower through a relay (VIII?) while otherwise the blower is powered through the resistor set. I'd say maybe a bad resistor set or bad connections to it.

Relay X might also be a possibility.

It shouldn't be a fuse issue, though, since both VIII and X get power through the same fuse (17).

Stromius

Welcome Pantera! Here's a thread to review: https://rennlist.com/forums/928-foru...operative.html

Post up a new thread on you and your S4!

JHowell37

Resistor pack.

blown 87

Be my guess.

Also, the new resistor packs need to have the harness connection rewired, simple to do.

SeanR

Ditto

WallyP

Relay, relay, relay...

Swap Relay X, the blower relay, with Relay VII, the defrost relay. If the blower now runs on everything except defrost, get a new 53 relay.

If the resistor pack fails, the blower will normally still run on the top speed.

pantera928

We have a winner!! THanks to all who replied. It was a flaky relay at the "X" position. You could wiggle it and it would click on and off and along with it the fan. I knew about this but was thinking too much instead of going on knowledge I already had. THanks again for the help.