No matter what, my heat is always cranking out the front defrost slots. It's not too bad in winter as it will warm up eventually (although it'd be real nice to adjust for some floor heat), but now in the summer, I don't even want to drive the thing. Anyone know what's going on? I couldn't even find a fuse for the blower to get by that route. Any ideas?

Thanks!

Obviously you want to fix the basic problem but the blower fuse is a 25 amp in the #5 slot on the under dash fuse panel on the '93. Your '91 is probably the same but I don't know that for a fact.

It's simply a matter of vacuum loss at the heater control valve and the mode switch. There is a vacuum reservoir behind the passenger side of the front bumper. Make sure it is not damaged or disconnected.

Well I found a plug got disconnected right behind the heat control board, so now the blower turns off when selected. Still no selector though. I was trying to find that vaccum reservoir yesterday, but nothing. I'll have to keep looking.

Cant miss it...https://www.google.com/search?site=&...hp.CsZ3_5KER-M

Had the same dashboard-only issue. It was a vacuum leak. In my case the leak was a 1/8 inch outside diameter vac line coming thru the firewall that rubbed against a heater hose and wore through.

If I hadn't been looking for a vac leak I wouldn't have found it because the wear-thru hole was hidden (where it was resting against the heater hose).

Cut the vac line and slipped a piece of 1/8 inside diameter tygon tubing over the ends - problem solved.