93 c/k 1500 v6 heat not very hot

I have a 93 with a 4.3L 6. I replaced a leaky heater core about a month ago. When I tested the heat, it seemed to get hot enough, but not quite as hot as it did last winter. I used the heat yesterday for the first time this season (the truck is in Virginia). It worked, but not very well. I had it turned up all the way to keep a comfortable temperature. The truck has a mechanical temp gauge that read 160 when the heat was up all the way. I turned the heat off, and the temp went up to 180 and after that, worked somewhat better. I have three theories:

1. It has a 180 degree thermostat instead of the stock 190, and if the truck isn't maintaining operating temperature, it means it probably went bad over the summer and I didn't notice because it gets so damn hot down here anyway.

2. The temperature door is not traveling as far as it should although this was not a problem last year, and the air works great.


3. The heater core was an after market part, and not a GM part. Could it be slightly different?

I'd go with number one. Put in a 190 degree stat and see what happens.

I agree with #1.

Also if the temp blend door is not going full travel it's allowing cool outside air to bypass the heater core.

I do not think the new heater core is an issue unless there is a blockage. At operating temp both hoses going to and from the heater core should be feel the same by hand.

you should be operating at around 190 deg F..many poor quality thermostats out there...I've had good luck with the stant brand/or ac delco..

one way would be to remove thermostat place in hot water to see at what temp it opens ...when replacing test new same way..

since this is a 1993 check vacuum lines/vacuum leaks this can cause the temp blend door not to work correctly...and as mentioned the heater hoses need both be hot...

this could be the air bubble in the coolant system . remove coolant cap run engine until at normal engine temp...rev to 1500-2000 rpm occationally see if the air bubbles out..