Cab heater

[INFChief]

First, my engine temp gauge doesn’t work. Did a visual inspection (except behind the instrument cluster) and will now go in a check voltages / resistance.

My cab heater is so anemic that it ought to be AC. The Dan blows in all 3 speeds and the vent/heater/defroster controls all seem to work. I will check to see if the heater temperature control cable is actually working.

My question is for you Trail Blazers; have you encountered something that’s been known systemic problem with the cab heaters?

TIA

 

[BERZERKER888]

following...

 

[Skyhawk13205]

How is your coolant level? I flushed and filled my coolant via a vacuum fill system.

You can also take your heater apart and check the cable to the heater core valve

The heat works well in my truck and it can get uncomfortably hot even here in Alaska at 20 deg with no cab insulation.

 

[Third From Texas]

Yeah, be it an A0, A1, or A1R...one thing these trucks excel at is cooking the cab via insane heat.

Nothing special about the system: hot fluid goes thru hose to heater core. Fan blows air over heat exchanger.

So given that the heat comes from the fluid, I'd say that something may be obstructing the coolant flow to/thru the heater core?

 

[Skyhawk13205]

Yeah, be it an A0, A1, or A1R...one thing these trucks excel at is cooking the cab via insane heat.

Nothing special about the system: hot fluid goes thru hose to heater core. Fan blows air over heat exchanger.

So given that the heat comes from the fluid, I'd say that something may be obstructing the coolant flow to/thru the heater core?

it would take about 30 min to check, drain about 5gallons of coolant, remove grill, seperate heater hoses open heater core valve and blow air through them or flush with a hose.

 

[Ronmar]

Yo

it would take about 30 min to check, drain about 5gallons of coolant, remove grill, seperate heater hoses open heater core valve and blow air through them or flush with a hose.

You don’t even have to pull the grill. Pull the heat control to get to the hot/heat position. Tip the cab and drain down a few gallons of coolant and disconnect the heater supply pipe off of the back side of the thermostat housing. See if you can blow some low pressure air thru that line back into the engine to confirm the heater valve is open and you have a passage thru the heater.

if the system is full to between the sight glasses, the pump should be able to circulate coolant up thru the heater core at higher RPM. Now if the pump impellar was eroded, or the belt is loose/worn it might have trouble pushing any air out of that heater loop. And if that loop has a leak it will suck air right back in the next time it cools…

 

[INFChief]

How is your coolant level? I flushed and filled my coolant via a vacuum fill system.

You can also take your heater apart and check the cable to the heater core valve

The heat works well in my truck and it can get uncomfortably hot even here in Alaska at 20 deg with no cab insulation.

Coolant level is correct; visible in the upper sight glass. Could still be a blockage in one of the lines to/from the heater core. Flushing might not be a bad idea. I plan on checking the cables & adjustments. They operate smoothly and the defroster & vents blow but that doesn’t mean the heater damper is working properly. Thanks for the helpful suggestions! I’ll keep you posted.

 

[INFChief]

Yeah, be it an A0, A1, or A1R...one thing these trucks excel at is cooking the cab via insane heat.

Nothing special about the system: hot fluid goes thru hose to heater core. Fan blows air over heat exchanger.

So given that the heat comes from the fluid, I'd say that something may be obstructing the coolant flow to/thru the heater core?

I’ll check on that. Thanks!

 

[INFChief]

Yo

You don’t even have to pull the grill. Pull the heat control to get to the hot/heat position. Tip the cab and drain down a few gallons of coolant and disconnect the heater supply pipe off of the back side of the thermostat housing. See if you can blow some low pressure air thru that line back into the engine to confirm the heater valve is open and you have a passage thru the heater.

if the system is full to between the sight glasses, the pump should be able to circulate coolant up thru the heater core at higher RPM. Now if the pump impellar was eroded, or the belt is loose/worn it might have trouble pushing any air out of that heater loop. And if that loop has a leak it will suck air right back in the next time it cools…

Belt looked good and tight. Will double check though. Yes; coolant was visible in the upper sight glass. I’ve been wondering if these systems need purged and whether there’s an air pocket preventing circulation?

 

[Green Mountain Boys]

With cool ambient air temperatures and an empty truck my truck takes a long time to warm up the engine to produce good heat. You said your engine temp gauge is not working so are you sure your coolant is really getting up to normal operating temperature? Maybe check with an IR thermometer.

 

[INFChief]

With cool ambient air temperatures and an empty truck my truck takes a long time to warm up the engine to produce good heat. You said your engine temp gauge is not working so are you sure your coolant is really getting up to normal operating temperature? Maybe check with an IR thermometer.

Good idea. I happen to have one. Will try to check in the AM.

 

[Ronmar]

The coolant loop is independent of the thermostat, so if the level is good, it should purge the heater loop as soon as RPM is increased.

yea the A0 is cold blooded as they sent the bypass coolant down to the trans cooler instead of back thru the block like cat intended. You have to warm up all that transmission mass and overcome all that radiating surface area as well as work it hard enough to actually become a heat source to get the coolant temp up…

be sure and hit all the hose clamps while yo are in the heater assembly

 

[Skyhawk13205]

With cool ambient air temperatures and an empty truck my truck takes a long time to warm up the engine to produce good heat. You said your engine temp gauge is not working so are you sure your coolant is really getting up to normal operating temperature? Maybe check with an IR thermometer.

I have an A1, with 4 hours of preheat via block heater and high idle with the exhaust brake in warmup it takes about 10 min to defrost the windshield and for the heater to produce decent heat.

if you were missing a regulator it would take a very long time to warm up. It could be your temp gauge is working but you don’t have a regulator. Prob good idea to check with a IR.

 

[Ronmar]

I have an A1, with 4 hours of preheat via block heater and high idle with the exhaust brake in warmup it takes about 10 min to defrost the windshield and for the heater to produce decent heat.

if you were missing a regulator it would take a very long time to warm up. It could be your temp gauge is working but you don’t have a regulator. Prob good idea to check with a IR.

With all the bypass coolant going to the trans cooler instead of back into the engine, you basically don’t have a thermostat anyway until the trans becomes a heat source.

They did away with the bypass on the A1/A1R so they warm up better/easier than an A0 does… Mmmm Exhaust Brake, Mmmm

You are right though, the IR will tell the tale…

 

[pman13]

I have a similar problem with my engine temp sensor not showing anything. Where should I point the IR at to determine what the issue is from?

 

[INFChief]

I have a similar problem with my engine temp sensor not showing anything. Where should I point the IR at to determine what the issue is from?

 

[INFChief]

You should check temps in numerous places. Make a list and write the cold start temps for all those places. Every couple of minutes do another temp check and record those. Continue doing that until you’re sure it’s reached operating temperature.

I would check:
1) the cab defroster & heater vents.
2) the top & bottom of the radiator
3) upper & lower radiator hoses at the engine
4) cab heater supply & return
5) any inlet & outlet hoses at the water pump
6) I would even check the coolant reservoir / surge tank

Capturing these temps could help narrow down any blockages or potentially problem areas.

Others may have better suggestion.

 

[Ronmar]

I have a similar problem with my engine temp sensor not showing anything. Where should I point the IR at to determine what the issue is from?

The temp sensor and the over-temp switch are mounted in the thermostat housing. That is the best place to shoot with an IR. You should see a temp difference between that and the elbow/ upper rad pipe until you reach the thermostat opening point around 178F. Once the thermostat cracks and allows flow, the housing and upper rad pipe should be about the same temp. On stainless and copper I usually shoot a small spot of flat black paint as a good/consistent IR radiating surface to measure off of. It also keeps me measuring at the same spots for comparisons…

 

[MrMikey4026]

Has the thermostat been removed?

 

[INFChief]

Has the thermostat been removed?

Haven’t checked.