No Heat inside cabin problem (and no A/C)

hmwave

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Searched the forum for information but couldn't find much.
Wondered if anyone has ideas on this problem, or if it's a known issue with a specific fix.

2003 Cobra has sat inside in dry garage for 4-5yrs, very seldom driven.

Took her out in Summer and noticed the A/C wouldn't blow cold. I put it down to possibly low refrigerant given the car has sat for so long.

But, drove her yesterday in 40-50F temps and there's no heat at all from the vents.
Tried rotating the controls multiple times, switching off and on, but nothing, no heat at all.
The fan is running and air is flowing proportional to the fan speed, and the air flow can be properly directed to feet, face, or windshield defrost with the control.

It's been a while since I spent much time working on her, but will dig in when I have time to determine the root cause, but wondered if anyone has ideas on what's wrong, what to check to resolve the problem.

Possibilities:
1) Air block or fluid lock somewhere in the heat exchanger, or supply from the block? Can I bleed it somewhere to resolve?
2) Not sure if the heat flow path damper(s) are electrically actuated so possibly stuck shut, an actuator(s) has failed, or maybe a fuse blown?
3) Seems odd the A/C wouldn't blow cold in Summer, and now there's no heat in Winter. Coincidence or maybe a clue of what's wrong?

Thanks for any advice.
 

UnrealSVT

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Searched the forum for information but couldn't find much.
Wondered if anyone has ideas on this problem, or if it's a known issue with a specific fix.

2003 Cobra has sat inside in dry garage for 4-5yrs, very seldom driven.

Took her out in Summer and noticed the A/C wouldn't blow cold. I put it down to possibly low refrigerant given the car has sat for so long.

But, drove her yesterday in 40-50F temps and there's no heat at all from the vents.
Tried rotating the controls multiple times, switching off and on, but nothing, no heat at all.
The fan is running and air is flowing proportional to the fan speed, and the air flow can be properly directed to feet, face, or windshield defrost with the control.

It's been a while since I spent much time working on her, but will dig in when I have time to determine the root cause, but wondered if anyone has ideas on what's wrong, what to check to resolve the problem.

Possibilities:
1) Air block or fluid lock somewhere in the heat exchanger, or supply from the block? Can I bleed it somewhere to resolve?
2) Not sure if the heat flow path damper(s) are electrically actuated so possibly stuck shut, an actuator(s) has failed, or maybe a fuse blown?
3) Seems odd the A/C wouldn't blow cold in Summer, and now there's no heat in Winter. Coincidence or maybe a clue of what's wrong?

Thanks for any advice.
I would suggest first starting with recharging the AC and seeing if the clutch on the AC compressor is properly engaging when the AC is turned on. The heat not working with the car warmed and fans blowing...from sitting so long could be due to a blockage in the heater core, faulty thermostat or poor coolant flow. Try and flush the coolant and see if that helps. Maybe replace the thermostat with a Reische Racing 170* thermostat.

Sent from my SM-G975U using Tapatalk
 

hmwave

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I would suggest first starting with recharging the AC and seeing if the clutch on the AC compressor is properly engaging when the AC is turned on. The heat not working with the car warmed and fans blowing...from sitting so long could be due to a blockage in the heater core, faulty thermostat or poor coolant flow. Try and flush the coolant and see if that helps. Maybe replace the thermostat with a Reische Racing 170* thermostat.

Sent from my SM-G975U using Tapatalk

Engine is running right in the middle of the temp gauge.

Presumably I should be able to feel heat on both sides of the thermostat tubing to see if it's opening?
I fitted a new thermostat years ago but don't recall if there's tubing both sides. I can check soon.

I'll also try the compressor clutch soon, see if it's operating.
 

BOOGIE MAN

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Burped the coolant system to make sure there's no air bubble in there?

"Nothing makes me question ALL of my life decisions like SVTP."

Posts and likes are not mine.
 

hmwave

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I burped the coolant when I replaced it a long time ago, but been years since that time, so maybe a factor. I'll check.
I recall the burp plug was a nightmare to remove. Nearly mangled the square drive hole.

The fans are definitely blowing as I get strong airflow from the vents, and feet are quickly freezing when I direct air downward.
The windshield defrost air flow is also working, water condensation quickly evaporates when I turn it to that setting.

hotcobra03: wasn't sure what you mean by heater core connected. The car is stock in that regard, so should be.
I don't have any coolant leakage, nor fluid on the carpets, so unless there's a blockage somewhere it should be working.
 

hotcobra03

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are you original owner?
heat core is a common issue with leaking

when this happens you can bypass heater core
fluid is always flowing thru

$40 core $500 to install type of thing
 

hotcobra03

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Home

scroll down to enter

menu on left svt document's

scroll down to service manual

small version will work on cell phone

will have section on hvac

tells how it works and how to fix by issue
 

hmwave

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I am the original owner.

I have the Ford large shop manual and electrical diags so will review.
hotcobra03: what a fantastic site! Thank you for sharing such a great resource.

Just FYI, me asking these questions...
I did all my own work years back, springs/shocks, MM caster/camber plates and sub-frame connectors, pumpkin brace, shifter, injectors, pulley, MAF, intake, tune, rotors/pads, 315/35/17 GS-D3's with offset discs to move aftermarket rims outward, McLeod street twin clutch, etc, etc, all the typical mods on these models.

I've just been out of the picture for a number of years so have long forgotten some of what was done and how, reason the car has sat mostly undriven for so long.
I'm expecting to get fully back into things in 2021, get her fully prepped for Spring/Summer driving.

One thing I do vaguely recall is the mod fitted at the back of the motor to flow coolant I think out the rear of the Heads.
There was an aftermarket part I purchased prolly around 2004/5 that changed the coolant plumbing. I recall it was a nightmare to fit so I think I had my local shop fit it when they fitted the McLeod clutch. I don't recall if that mod messed with the heater coolant flow or is unrelated so not a potential factor regards this problem.
 

shurur

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Just look on the passenger side firewall and see whether the heater hoses are connected to anything.

Crack pipe HCM runs from backside drivers side head to back side passenger side head, then to heater core supply (firewall) then out from heater core return (firewall) to valley (under intake) hard line.

Maybe they bypassed the heater core altogether...as someone mentioned above.
 

hmwave

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Sorry folks, no news.

Pressure of work in the medical field means I won’t have time to look at the car in any depth for a while yet.

As soon as things quieten down I’ll be sure to troubleshoot and close the loop on this thread.

Good news is you’ve all given me a good head start on what to look for!
 

SecondhandSnake

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A couple points on this one-

The heater core gets flow regardless of the thermostat. In fact, it gets more flow when the thermostat is closed, and a higher temperature thermostat would give you more heat.

If/when flushing the system, you want to back flush the heater core. That is push water in from the heater core outlet, and let it drain out the inlet. You would not believe how much crap will come out.

I would also look into the actuators for the system. They're vacuum actuated. I don't recall the specifics of how it's set up on these cars but I would wonder about a blend door on it.
 

shurur

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A couple points on this one-

The heater core gets flow regardless of the thermostat. In fact, it gets more flow when the thermostat is closed, and a higher temperature thermostat would give you more heat.

If/when flushing the system, you want to back flush the heater core. That is push water in from the heater core outlet, and let it drain out the inlet. You would not believe how much crap will come out.

I would also look into the actuators for the system. They're vacuum actuated. I don't recall the specifics of how it's set up on these cars but I would wonder about a blend door on it.

Yes there is a single vac hose that goes into the firewall by the ac core connections that makes all those actuators work. The rubber parts of the hosing often rots out and the plastic cohline is a favorite with rodents of all kinds. Good point.

You can replace that hose with 3-4mm ID silicone or Mercedes 1mm ID cohline.
The silicone will slip over the snipped cohline to replace whole choline sections or just to be used as couplings for whole lengths of cohline.
 

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