Heater core bypass

My 88 Fox seems to always provide heat inside the car from the heater core. Some days worse that others. Yes, the user temp selector is in the middle field between blue and red. Yes, I tried it all the way to the left in the blue field as well. This has been going on for many years since I got the car 12 years ago. It has AC. Its been checked for low and high side pressures. Its been evacuated twice. Its been topped off each year. The best cool temp inside the car will match summer shade temps.

Went down to the hardware store and got a male 3/4" to female 1/2" zinc coated pipe adapter, and a 3" long 1/2" threaded zinc coated pipe, connected the 2. Also got 3' of 1" heater hose, and same length in 3/4" heater hose and new hose clamps. Jumpered out the heater core by running the 1" hose from the port off the rear of the head to my pipe adapter, then from that to the 3/4" hose, routed and connected to the pipe at the back of the engine behind the oil filter housing. No apparent leaks or drips.

Now the AC can and does cool the car to a more tolerable temp since its not fighting the engine's coolant heat inside the car.

Unlike the conclusion of the Mythbusters TV program, my car does obviously use more gas while using the AC. Its working alot harder on hilly terrains. Acceleration is more labored, and takes longer.

Reply to
Jonny
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It seems you have found a fix that works for you. Cars tend to have one of two ways of controlling temperature (other than those problematic computer controlled things). One is to control the amount of fluid flowing through the heater core. That is the way my 1965 Sunbeam Imp did it as well as many other cars of that age. Today more tend to control the air flowing through the heater core. I am going to guess that is true for yours.

The "real" fix is to fix or replace the part that is no longer working. Some are controlled by wire cables and others by vacuum powered dampers. A simple vacuum leak or loose hose or a rusted or bent cable can be fixed, often cheap if you do it yourself. The real difficulty is finding it and getting to it.

BTW your fix is real, just not the same as the "real" one. :-)

Yep, It does vary depending on the car. In general the smaller, lower powered car will show a larger difference when the AC kicks in.

Reply to
Joseph Meehan

Great solution for the heating problem! It would be a service to other VW owners if you would post your fix on the VWVortex Fox forum

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. If you do, please include pics.

Reply to
Papa

The Fox's heater core line has a history of overpressure. Some have even dumped antifreeze in the passenger compartment. A fix was provided by VW by the dealer for these as a patch. Basically its a small box with high pressure sensing that dumps some fluid to the outlet side hose without it entering the heater core. This is installed on the Fox.

The only user operated cable used mechanically diverts air flow from the heater core to the AC evaporator. No electronics involved, straightforward.

I can feel hot air emanating from the heater box further left, not the heater core itself when all is off before the fix I mentioned. The AC, when engaged, before the fix mentioned, still put out cold air at the vents.

The TV Mythbusters used two identical Ford SUVs with a V8 engine. They found no fuel usage difference using or not using AC, even with the windows open with AC at MAX. I found this as not believable myself.

Reply to
Jonny

what this says to me is that the door that diverts air away from the heater core has had the foam on it disintegrate (the plastic backing has holes in it to make it easier to move,) a more "correct" fix would be to disassemble under the dash and put something on that door to block the holes that are now exposed now that the foam is gone.

Of course, if you live in a climate that is warm enough that you don't need the heat, this is a non-issue.

As an aside, on the A1 chassis cars that used a valve in the heater hose, I've had to replace a few of those valves as well as when they reach a certain age they tend to allow coolant to flow through the heater core even when the valve is in the closed position.

nate

Reply to
N8N

I should add that this seems to be a common problem in older water-cooled VWs. My '88 Cabbie has the same problem, as does Cabbies owned by several of my friends. Fortunately, for Cabbies at least, there is a manually operated flap on the dash that helps to keep the heated air from entering the cabin.

Reply to
Papa

Reply to
none2u

You're right, the "door" itself is probably the culprit. That's another problem fixing it. I had the VW looked at by a VW specialty shop in VA Beach, VA. They took the dash and all out down to the firewall to get to the heater core and box its contained in. I don't intend to do that.

Reply to
Jonny

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