HELP! Heater issue in 1989 blazer

[SC-Texas]

OK, for those of you that have been enjoying my A/C saga, here's a recap- after lots of time troubleshooting and fixing various issues with the duct system on my blazer, the A/C was repaired. It blew cold air. On the coldest day of the year (so far) in Houston, TX (yes, it was a cool 50f), I had A/C that blew through the correct vents and ducts when it was supposed to.

The problem was that the heat had ceased to work.

So, here is my problem matrix that I need help with:

1. Problem: Heater not working.

2. Remedial steps:
a. Removed both hoses from heater core to check flow. No flow from either hose.
b. REmoved the hoses:

3. The nipple at the water pump is clear and unclogged-No flow from this

4. Hoses are not clogged

5. The heater core is unclogged and flows freely

6. Replaced Water pump. Still no flow at the heater hose nipple on the waterpump.

7. Thermostat: it is in the closed position when pulled ==> appears to be working

8. Miscelleaneous: Intake has been replaced, I beleive that the original heater hose ran from the back of intake to heater core and not from waerpump nipple to heater core.

9. Anyone have any suggestions? I and my mechanic are at a dead end on this one unless the waterpump is bad.

I can't see how there would be a differnence in flow between a nipple on the waterpump and a niple coming off the back of the intake.

Any ideas or suggestions?

 

[dyeager535]

I think there were SOME variations, but more often than not, the heater hose nipple should be on the intake manifold. You think this is the way it was, you are more than likely correct.

The intake is pressurized by the water pump (entire engine in fact) so the nipple is usually on the intake to force water through the core and back to the radiator. I made the mistake of using the water pump, and as you've said, there is no pressure there...that's an inlet in most cases.

That's all I have to add, hope it's that easy.

 

[SC-Texas]

That about sums it up. I'll add a "t" into one of the intake manifold's two access points and run the water temp and the heater off the "t".

 

[4X4HIGH]

On my 89 blazer the heater hose does come from the back passenger corner of the intake manifold to the heater core, then from the heater core to the radiator for the return hose. On the older trucks the heater hose ran from the front corner of the intake manifold to the heater core then the return hose went to the radiator.

 

[SC-Texas]

Problem solved. My mechanic fashioned a Brass T-Fitting and inserted that into the intake access point. The heater hose was on one side and the temp guagge sending unit on theother side ofthe "T".

The redneck Mobile now has A/C & Heat!

Thanks to everyone who helped!