86 Volvo 740 Turbo NO HEAT =:0(~

My 86 Volvo 740 T Named Thelma, is having problems. Poor gal, first the
heater fan went, I replaced that, now all of a sudden NO heat. It has
been cool heat the last year anyway but NONE now. I got pooking around
and found the Vacuume line to the heater valve (on the top line to the
heater core) broke. So I fixed that with some vacuume line. Still no
heat. So now I wonder is it the Heater Valve, the heater core blocked,
or is Thelma just giving me a hard time...LOL
I love the car, but its cold up here in Maine right now and hard to
drive when cold...
Thanks if anyone has any ideas.
David
Portland, ME

=:0)~

 

Once the beast warms up, check the temperature of the return line
heater hose (runs from the heater core back to the engine) to see if
it's warm/hot.

If so, no obstruction in heater control valve or core.

 

Hey,
Thank you... And if the return line is not hot? How can I tell if the
heater valve is working? If I push the lever thingy, it pushes in.
Thank you
David

 

Hi there,
OK, I went and ran the car. The Valve is on the lower hose. The hose
before and after the valve is hot. The hose coming off the top is not
warm at all. Im guessing the valve is ok?!?! The heater core is
blocked? If so how do I get it unblocked? Will flushing the whole
system make it better? Is there a way to flush the heater core by
itself, with out removing it?
Thank you
David

 

I can only speak about the vehicle I have done this on, a 1981 244, but
assuming the layout is similar...

Remove the panel to allow acces to the heater control valve (on the
244, it's above the gas pedal, slightly to the right, near the
firewall).

Move the temperature control handle while watching the movement of the
heater control valve; if it feels normal, with slight resistance, the
valve is probably OK, and the problem would lie with the heater core,
which is "downstream."

To confirm: feel the temperature of the hose leading from the heater
control valve to the heater core, to see if it is warm/hot after car is
warmed up.

If it is cold, and the temperature control handle is in the full open /
hot position, the heater control valve needs to be replaced.

Otherwise, the core is toast (obstructed).

Of the two scenarios, the heater control valve is the more likely
culprit.

 

Sorry Im confused.
The two hoses that go through the fire wall do not go directly to the
heater core? What is the Heater control Valve? Is that the one that is
in the engine compartment on the 740, on the bottom line going in to
the heater core? If so that is hot both before and after. If it is the
core, can it be flushed while still installed?
I hope its the heater control valve, but Im thinking its not.

 

Pull the control panel out and check the white vacuum line to make sure
it is not pinched or crimped. Check the vacuum lines just to the right
of the gas pedal for the same thing. Usually the vacuum supply pipe gets
crimped and there is no vacuum to the heater control valve.

Bob

 

Easiest way is to remove the valve and run water through it, pushing the
lever should open or close the flap.

Sometimes these old valves get fragile though, some are plastic and I
broke the pipe off of one, but then if that happens it was ready to go
anyway.

 

700 series is completely different, the heater valve is vacuum operated
and is located in the engine compartment.

 

Awesome...Thank you all..
Ill try those things today and see. Hopefully its vacuum line or the
valve, hate to think its the hater (Ha ha) core. (Heater core).
Will let you know...

 

OK I did some trouble shooting. I think it vacuum, BUT the cable to the
dash control is broken in the plastic wher it screws on. So I ordered
one from Volvo. Gonna be a hard change but worth it if it fixes this. I
also found this on line as well.
http://www.volvoclub.org.uk/faq/HeatingAirConditioning.html#MCCClimateControlACNotWorking
Will let everyone knwo what happends.
David

 

OK I did some trupble shooting. I think it vacuum, BUT the cable to the
dash control is broken in the plastic wher it screws on. So I ordered
one from Volvo. Gonna be a hard change but worth it if it fixes this. I
also found this on line as well.
http://www.volvoclub.org.uk/faq/HeatingAirConditioning.html#MCCClimateControlACNotWorking
Will let everyone knwo what happends.
David

 

Are there any 740s in USA/Canada that do not have air conditioning, or is it
a universal thing?

All the best, Peter.

700/900/90 Register Keeper,
Volvo Owners Club (UK).

 

I'd be shocked if the heater core were the problem, that'd have to be
one heck of a clog!

My guess is a vacuum line cracked, haven't had that happen on the heater
valve but I've had plenty of other vacuum lines do that, some of the
ones in the '88 Saab literally snapped in half when I pushed them out of
the way. They'd turned completely hard and brittle.

 

It's universal, all 700 and 900 series cars came with A/C, EFI, power
windows and heated seats. Every one I've ever seen had a sunroof too,
though I've heard rumors that some came without.

 

Volvo has the opposite problem. THe tubing is so soft it collapses and
kinks when the weather is hot and takes a set in the collapsed form when
the weather gets cold. Sometimes there's enough cold from the A/C to set
the hose in the summer and then none of the inside vents work either.

Bob

 

In Canada, all 85 740s came without A/C, but all had the A/C adaptable
heating system. Most had A/C installed at the dealer level. In
1989/1990, some of the cheaper models (740 with no letters) came without
A/C (and cheaper interiors and steel wheels) to try and get their list
price down. The price of the dealer installed A/C was so ridiculously
high that they ended up having promotions to give A/C away as very few
people paying "Volvo money" were interested in a car without A/C.
(These down contented cars also came without a sunroof.)

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

Interesting, yet another case I was unfamiliar with of strange versions
available in Canada.

For the US though my previous statement still applies, if there were any
exceptions, they're extremely rare.

 

OK so the dealer called and said the cable is back ordered. does anyone
know where I can find a cable after market maybe? ITs 65.00 thought the
dealer... OUCH...
Hope this fixes it...
I did find that one vacuum leak out by the water valve, heater valve,
what ever they call it right now. Only think is, I need to find the
solid line, the soft vacuum line wont hold up once its warm out. Any
ideas?

Thanks guys,
David

 

I might try voluparts in Atlanta: http://voluparts.com/
or vlvworld in canada: http://vlvworld.com/

They deal in used and new parts. You might find a good used one a save
a few bucks

Regards
Russ