Heat.

[trife86]

In my 89GM. a/c works kickass but the heat is kinda weak. it will get hot for a few minutes than go to room tempature and stay there. i have no idea what can be causing this.

I used to work at a cab company and i remember the mechanic there with alot of cars that had bad heat would go through the glovebox and i guess uplug/plug something in so it has good heat but when summer comes back around you have to go back and re-do it. i guess this is a cheap way around? If so im looking to check that out.
Engine temp always stays the same so i think that would rule out the thermostat. but thats all i can figure

[85crownHPP]

you are correct - open your glove box and reach in to find a pretty large brownish/clear vacuum line. Thats the blend door - pull it, cap it, and get ready to be roasted.

Cleaning or replacing the temperature sensor behind the dash (above the glovebox) might fix this problem, so they say.

[trife86]

you are correct - open your glove box and reach in to find a pretty large brownish/clear vacuum line. Thats the blend door - pull it, cap it, and get ready to be roasted.

Cleaning or replacing the temperature sensor behind the dash (above the glovebox) might fix this problem, so they say.

Good stuff im going to try that out tommorow as its dark out now, So what do i just put it back together in the summer?

[Archangel]

Trife86, if your heating works at least as good as mine, you won't wait till summer to fix it - half an hour after the engine's reached its normal temperature inside the car it'll get so damn hot, you'll have to open a window so you don't fry. The part that's failed is the ambient temperature sensor, it's the thermostat of the automatic HVAC system the boxies have, and it's a common problem. To fix it you can either go and buy a new one for about $35, or just go to a junkyard and pull several of them at once, chances are at leas one's gonna be good. Don't remember how it was with the GMs, but in Town Cars it's very easily accesible, right under the dashpad, and it's the same part - to make your life easier just steal the sensors from Townies.

[marquisman]

what happens if you have the regular temp control and a carb, and you changed the rad, heater core and t-stat?

[trife86]

well i capped off the vacuum line as suggested and in about 50degree weather all was well hot heat. but now in 30degree weather 70degree heat at best, meanwhile my 1990 towncar blows fire.

Im thinking maybe i didnt seal off that vacuum hose good enough? what should i use to seal it?.

If my heatercore was FUBAR than wouldnt it go hot cold hot cold?

[Archangel]

Marquisman, are you not getting heat too? Dunno about the manual controls, all the ambient tempsensor controls is the blend door, so unless your blend door or the linkage to it (cable I assume) are messed up you should be having no problems.

Trife86, there are rubber plugs available for vacuum hoses, look at the problem solver's section of your local auto parts store. Or just use s suitable size bolt that is long enough as to have some 1/4" long smooth wall near the head - cut the threaded part of the bolt so you only have the smooth cylinder and the head, and stick that in the hose. The blend door on an ATC-equipped vehicle is spring preloaded, when there is no vacuum applied to its servo the spring pulls the door to "full heat" mode shutting off the outside (cold) air completely. That spring on my TC is so strong, that when you disconnect the vacuum line the blend door closes with a loud metal bang. In your case I'm thinking it might be either something obstructing the door's motion (tired spring, gunk piled up at the hinges), or just your heater core doesn't have enough flow... test it with the vacuum line reconnected to the blend doot, the heating set to 65 (I think that's as cold as it gets), and blower motor turned off, when the car warms up at idle the supply and return hoses of the core should have the same temperature, which should be close to that of the return hose of the radiator - if the supply hose of the core and the return hose of the radiator are the same temperature, but the return hose of the core is cooler, that might be an indication of partially clogged heater core.