WTF? My heat doesn't blow hot...

[SHOhhhhMan!]

Well, I noticed a small quirk with my car the other day. It was a bit chilly out at night and I wanted the vent temp to be 75*F or so. Well, I turned it to 75, but it didn't get any warmer. So, I cranked it to 90 and still no heat. The cooling system is operating properly and indicating normal temps on the gauge. It acts just like it always has, but I have no heat. As far as I can tell, there is no coolant loss, so I'm doubtful the heater core took a crap.

So, what could it be? My EATC works perfectly, except for no heat. Is there a line that could have gotten kinked or something? Or is my blend air door stuck or not operating? Anyone ever had this happen and what did you do to fix it?

Thanks!

 

[Mr Anonymous]

Try the EATC self-test (instructions on SHOTimes IIRC) and see if you get any codes. It could certainly be a blend door problem (which should generate a code), but usually ends up being a heater core blockage. In any case, either is a major PITA to replace.

If the EATC self-test comes back clean, then you might next want to disconnect the two heater hoses going to the heater core and see if you can force any air or water through it.

 

[SHOhhhhMan!]

Well, test came out clean with an 888. So, time to check the hoses. Any other tips/ideas for stuff to check?

 

[Rob94]

Do what Mr. A suggested. If the EATC self test came back OK, it very well could be a blockage in the heater core.

 

[SHOhhhhMan!]

Well, the problem solved itself. I was coming home from work and it was raining, so I had the EATC turned to 70*F with it on floor and def. I noticed that the air wasn't blowing as cold as it had been, so I turned it to vent and cranked it to 90*. Works like a charm now. Hopefully it stays that way. I just recently replaced the radiator and the waterpump, so it has new coolant in it and the system is free of leaks.

 

[DHMag]

when the heater control is set on Defrost, the A/C cycles. this means you are mixing cool air with warm air. if you want straight heat, select Floor and blast away at 90*.

during most heater core replacements, most ppl dont reinsulate the sides of the heater core, allowing cooler air to seep around the edge of the core, between the core and housing. air is like water, it will take the easier path. heater core fins produce resistance, so the air will "blow-by" the heater core, through the aforementioned gap, thus resulting in less warm air being moved into the passenger cabin.

 

[SHOhhhhMan!]

Uh, FYI, the A/C always cycles when it is on, regardless. About 20psi to 40psi is what the R-134a system on SHOs cycles between. 40psi, compressor clutch engages, drops to 20psi, and it disengages. When you turn on def. the A/C comes on for the sole purpose of dehumidifying the air. The blend air door sets to the full hot position at 90* and forces all the chilled and dehumidifyed air through the heater core. The A/C in these cars comes on when you select MAX A/C, Panel & Floor, Floor & Def. and Def. Otherwise, Vent, Floor are your only options for non-A/C temp control. Now, if the heater core isn't hot because of a blockage, then you're going to get no heat in any situation, regardless of what position the blend air door is set at or what mode doors in the plenum are doing.

I highly doubt that not reinsulating the outside of the heater core is going to have a tremendous effect on the temp. The coolant in the heater core is usually going to be about 200*F since it's in the primary circulation of the cooling system and is the first place coolant goes after flowing out of the hot engine block. The radiant heat should be more than enough to make a very sensible heating effect on the air, regardless of where exactly it passes.

when the heater control is set on Defrost, the A/C cycles. this means you are mixing cool air with warm air. if you want straight heat, select Floor and blast away at 90*.

during most heater core replacements, most ppl dont reinsulate the sides of the heater core, allowing cooler air to seep around the edge of the core, between the core and housing. air is like water, it will take the easier path. heater core fins produce resistance, so the air will "blow-by" the heater core, through the aforementioned gap, thus resulting in less warm air being moved into the passenger cabin.

 

[yamahaSHO]

If you use the "Vent" function and set it to 90, the AC does not cycle.

 

[SHOhhhhMan!]

If you use the "Vent" function and set it to 90, the AC does not cycle.

Fo shizzle. Unless it's really hot, (85+ degrees) I usually just set the vent to 60 and drive with the windows down because I hate how much harder the car gets to drive with the powerloss from the compressor and the fact that the clutch is constantly engaging and disengaging. I never noticed this on my Thunderbird since it had gobs to torque down low, but the SHO really takes a hit when the compressor clutch engages.

 

[yamahaSHO]

85+ is really hot??? Shoot... I'll drive with them open in 95+

Yes!!! You can really feel the difference when the AC is on.... I hate driving with it on.

 

[SHOhhhhMan!]

85+ is really hot??? Shoot... I'll drive with them open in 95+

es!!! You can really feel the difference when the AC is on.... I hate driving with it on.

Ok Arizona boy. I guess living in a climate where you can cook eggs on your hood kinda changes your perception of "hot".

 

[AutoSHO]

At this altitude we really get hurt by the A/C due to the horrible altitude spark tables. Can you say no timing advance? After adding some timing to my car I noticed that the A/C wasn't nearly as noticeable.

 

[Egg]

Could be a bad vacum valve going into the heater core, I had a friend with a ranger have this go bad on him, maybe yours just got stuck?