weak heat

[86VickyLX]

yea theres no lettering or numbers so im pretty sure its the basic climate control. we have more then one thermostat? i changed the one right on top of the waterpump. the engine warms right up no problem. it does take a little for it to warm up but it does

only one thermostat. How long does it take for your engine to warm up?

[import convert]

since its like 30s here if i just let it idle itll take like 10-20 to get wihtin the normal temp area. if i drive it straight to the highway itll be warm in a few minutes. i just changed the thermostat like 2 weeks ago too

[import convert]

anyone know of a way to test the heater core for clogs? this week i think ill change my heater hoses to make sure none of them coolasped or is cloged since my heat is still weak

[gadget73]

Not really any way to test them that I'm aware of. I'd try flushing it backwards to see if any chunks come out. If that cooling system was really nasty, its entirely probable the core is clogged.

[import convert]

im just trying to do what i can before i try changing the heater core since theyre a pain in the arse to do. i could try that and see what happens though

[biglinc1]

had similar problems on that old 1979. did a backward flush, changed the thermostat and problem solved. the backward flush got out so much crud in that system too. It had the atc system on it

[import convert]

hmmmm. i guess ill have to try doong that then. now did you just hook a garden hose to it or did you use somethign else?

[BigBiscuit]

Hey guys, I found your thread while searching on weak heat.

I have standard climate control, a new core, a core box with functional temp regulator door, new radiator, and a new stat, although I'm not sure what degree stat was installed. I still get lukewarm heat even though the motor warms up to what feels like op temp (no temp gauge in cluster), the supply and return hoses to the core get hot, etc.

two questions:
1) what temp rating is the OEM stat for an 88 GrandMarq?
2) could my AC system be activing somehow (shorting perhaps) and cooling the air charge that blows over the heater core? The AC doesn't normally work, by the way, but i'm desperate to understand why I could put my hand in the heater box this weekend and i got lukewarm air when the core was hot and by all accounts, the air temp should have been toasty. it's got me baffled and more than a little frustrated.

the problems you guys are describing sound similar to mine. I'd love to hear if any of you have found the answer.

[gadget73]

1) 195 degrees
2) no. Even if the AC were running, the temperature control is from a blend door. basically it will stop pulling air through the cold side and force all air to come through the heater core. If the blend door isn't pulling all the way to hot, then you'll get sort of crap heat. Is this an ATC car, or do you have the regular manual temperature control? ATC will have temperature numbers printed on the slider scale, non-ATC just has 'hot' and 'cold'.

I run a 180 tstat in my car, and it will still run at low roast temperatures if I turn it up too far. The 195 did make for better heat, but it was bad and making the car overheat in the summer.

[import convert]

im still having problems with mine. i flushed the heater core itself and it doesnt feel much better and didnt even seem to be clogged. the wierd thing is that at idle the heat feels the strongest and on the street its not much worse but on the highway it feels weaker and it changes depending on how cold it is. like with the slider on hot the car most of the time is comfortable. its weird. maybe the mix door is stuck open, idk but it bugs me cause i have plenty of vacume in the lines. the cable has no slack for the slider (manual temp) and i dont want to change the heater core if i dont have to and i dont think its the problem. im lost

[BigBiscuit]

gadget73, mine is non-ATC. my blend door is working...just pulled it out Saturday and checked it, lubed it, double-checked it prior to install, etc.

import convert, you and me included. i'm taking mine to my mechanic tomorrow. i'll post anything i find out because it sounds like you and i have similar problems.

another general question to anyone who might know: there's an electrical and vacuum hookup on the firewall right above where the core box installs on the other side. does anyone know what these controls do?

thanks for your input, guys.

[import convert]

ok so now i feel like a dumbass. i found out what was worng wiht my heat and it was me. i didnt know i needed to have the slider on max AC or OFF to open the recirculation door and keep the fan form pulling in outside air.

i was at school and looked through all data and found a few system diagrams and found out that nothign was wrong. but yea so it works fine.

[86VickyLX]

ok so now i feel like a dumbass. i found out what was worng wiht my heat and it was me. i didnt know i needed to have the slider on max AC or OFF to open the recirculation door and keep the fan form pulling in outside air.

i was at school and looked through all data and found a few system diagrams and found out that nothign was wrong. but yea so it works fine.

Very nice. Well at least you found out what was wrong. Glad to hear it's all good now.

[import convert]

i would never think that itd work like that though. i think its stupid but oh well, least it works

[86VickyLX]

yeah that's the important thing.