Wimpy heat

[Whitehorse]

I have a 95 and the heater doesn't work very well (blows cool air). My water temp gets to about 185 to 190 and my oil temp never gets to 215. The water temp seems normal but the oil temp seems very low. Should I be looking at my thermostat or is this likely something wrong with my heating and air conditioniong system? I have the automatic temperature control option.

Thanks in advance.

Rick

 

[86-ZZ3]

Can't help you with a LT1 but my L98 (classic small block) oil temp generally runs slightly more than the coolant temp at cruise (0-10F more) so yours sounds within normal. Oil pressure drops to 240 kpa at idle and around 420 kpa at cruise (2,000 rpm). I'd venture to say your thermostat is o.k. Check the coolant lines running to the heater core. If they're warm/hot, I'd say the HVAC system needs to be looked at.

 

[jmccloud]

Wimpy Heat

Welcome to a great site; lots of info here.
Three likely causes; bad ambient or interior temp. sensor, clogged heater core or stuck temperature door. They're easiest to fix in that order.
A bad ambient (outside) air sensor can cause low temperatures. To test, set the temp control as high as possible. If you get heat, replace the ambient sensor that's located in front of the lower passenger side of the radiator.
The heater core can be flushed reverse/forward with a garden hose. Use limited pressure as the core only sees 15-18psi in normal use. Also there's a 'flow control' in the line to the core that restricts flow at high revs. That flow control is plastic, black, about 2" long and located in the heater line below the black pressure tank, just in front of the firewall. It's a good place to disconnect for flushing. Flush or replace the flow control too (<$15 at the dealer). Take the heater lines loose somewhere other than right at the core as it's really easy to damage the core by pulling on the nipples. And don't get water on the optispark that is located below the water pump.
The temperature door can be seen by removing the module that's mounted on the blower housing, just forward of the firewall. Observe the door's motion by watching while a helper adjusts the heat. Booger to get to if it's broken. Use search above or an FSM (red, two volume factory service manual ~$100 on fleabay or ~$135 new from Helm Inc.)
A more remote possibility is air debris blocking flow thru the A/C evaporator. Not likely if you get good A/C.
Windy but hope is helps.

 

[John Robinson]

Vacuum problem

Before you do a lot of work check out this vacuum valve it controls the heat and the cruise.







This is a check valve and depending on which side is bad either the cruise or the climate control will be affected.

 

[rmagee7]

fur sure check all your vacuum lines had fits with mine untill i got to looking on my L98 had a micro crack in the line going from the right rear plenum orfice to the check valve in front of the distributor replaced the line and lo an behold my cruise and my heat started to work like new this all started outafter i installed a new cap! look for vac leaks and get a fsm to track all the vacuum lines and replace worn or broken lines that hard plastic junk that GM used for vac lines is prone to stress breaks and do get brittle with age,also does your heat get warmer at about 1200-1400 RPM if it does look to your air door control motor,good luck!