Piston Slap: HVAC Heartaches Beset Panther Love?

Sajeev Mehta
by Sajeev Mehta
piston slap hvac heartaches beset panther love

Peter writes:

I got a case of Panther Love and bought a nice 89 Town car. It’s a lower mileage (62k) girl, one that has been taken care of. I DD it.

I have been busy fixing everything that breaks on it. Previous owners just didn’t use her much, and so a wide variety of stuff just goes out. Window regulators. Alternator, battery, alignment, tires…… the list goes in and on. Every week something happens. That’s ok, and I expected as much. The engine, body, interior and tranny all seem good-superb.

It has of course an automatic temp control HVAC system, and and already I have been chasing numerous gremlins. Started with needing a new heater control valve as the floor setting never worked for the heater. That was an easy fix. But now it seems she has vacuum leaks under the dash or in places my good mechanics can’t find under the hood. Leaks that cause the system to do weird stuff, like sending all the air to the defroster under acceleration, and or switching from Heat to ac and back just for a moment. They have run all sorts of vacuum tests under the hood and can’t find the problem.

My questions is this: I have very good vintage car mechanics, but they charge 140/hour and it adds up quickly. And they are not HVAC specialists. They will gladly troubleshoot if I let them. Pull the dash and start poking around. That’s the next step.

Is there not a better way? Does an Ford (or any manufacturer) Vintage HVAC mechanic exist somewhere, someone who already knows the system? Seems to me that the experience curve might be mighty handy here. Something like a Lincoln doctor who is board certified in HVAC. That would be too cool. I can dream, no?

Or should I just stick with the guys I have and hope for the best while paying the man. I live in the Washington DC metro area. I am obviously not capable of doing this myself.

Sajeev answers:

You could find a retired Ford tech willing to help via Craigslist wanted ad. Only one way to find out!

I suspect you’ll find a simple repair once you look inside the dash: having disassembled multiple 30+ year old Fords (including an ’88 Town Car) I have little fear, but anyone with plastic trim prying tools, patience and common sense can do this in a matter of hours. I bet the main problem is a vacuum leak (i.e. going to defrost at low vacuum/full throttle) from the hard plastic hose going through the firewall and back into the engine compartment.

Or maybe you’ll get lucky and a smartphone based inspection camera finds the problem after removing the glove box?

I reckon you’re in the same situation as a previous Piston Slap query: a vintage auto tech needs to loosen/remove the dash, inspect and learn by doing. Honestly, it’s a simple system (as far as automatic climate control affairs go) and this is a good time to install a new heater core and clean/replace the A/C evaporator too: as time goes by both will need attention.

If you want to save some cash, take apart the basic bits on the dash yourself: the fake wood, stereo, glove box, dash top, kick panels (the dash normally bolts to the body behind them) before taking it to your mechanic. Buy a factory shop manual for any 86-89 Town Car on eBay for cheap if you need an exploded diagram for reference. It will come in handy for plenty of things in the future!

Since this is your daily driver, this is also a good time to replace all the T-10 bulbs with a bulk order of natural white LED lights (eBay, amazon, etc) to keep the wiring healthier (i.e. not bake) and reduce the load on your battery. Ask me how I know.

[Image: © 2017 Sajeev Mehta/TTAC]

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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