Hey guys, I had a thread a week or so back asking about a deal on a 740. Well, 2 days ago I went and checked it out. I didn't know what to expect for only $500 but I think I got a pretty good deal. Everything is running fine, I gave it a nice vacuum and scrub down. I just had a couple questions.

I just want to know how to troubleshoot AC. The fan has plenty of blowing power, but the air isn't cold. Where would I start to try and fix this?

The radio makes a popping noise randomly. I know it's not the speakers because I can put in a tape and it will play fine without the popping. It's only when I play the radio. The power antenna is bent and broken, but it is still sticking out, could this be what is causing the popping? BTW, every time it pops, the letters ST come on in the little display. I looked that up and it means stereo, but I don't know how that would make it pop.

Also, the interior is missing a couple plastic pieces. Like the one that surrounds the radio and cigarette lighter, and the one that goes on the door around the buttons and door open handle. Is there some place that I could get these? Thanks

The model is 1991 740 wagon with a b230F engine. I'm loving it so far, looking forward to making it better! Anything else I should know?

 

First thing, the 740 i believe has an interference engine. What that means is if you blow the timing belt, you ruin your the whole engine as the valves will get smashed. So make sure your timing belt is in good condition, or better yet, change it. But if you do, make sure you know what you're doing, as incorrectly turning the sprockets will wreck it too.

For the plastic pieces, you need to rifle through junk lots. Things like that you might be able to buy new somewhere, but it's not going to be worth the money.

FM radio is different from AM because it can transmit stereo sound (i.e. two independent speakers). However, if it's a weak FM signal, it will generally only transmit mono sound. The way most stereos indicate whether they are receiving mono or stereo is by some indicator like ST. My guess, and I don't know this for sure, is your radio antenna is crappy and ever so often it has a strong moment where it gets stereo. Maybe that translates as a pop or surge to speakers. Just a guess.

I am going to go out on a limb with the a/c and say it needs to be recharged. This isn't generally cheap ($200), but it's a common reason for A/Cs on old cars not to blow cold.

Also, congrats on getting a fine automobile!

 

Thanks for the reply! That's what I thought would be wrong with the radio, my antenna is bent because the previous owner said it retracted while inside and hit the ceiling. Is there a cheap replacement I could get somewhere online?

Now that you said that it's an interference engine kind of scares me, I'll look into that more and see if I can get it checked or replaced right away.
EDIT: I just found out its a b230F engine, so it's not the interference.

 

The 16 valve is an interference engine; the 8 valve B230 is not, so you're okay there. I'd put the timing belt fairly high on the to-do list though, unless you know when it was done last. Volvo recommends replacement every 50K. Busted belt won't bend the valves on this engine, but it will definitely spoil your day.

Hot AC is most commonly due to lack of sufficient refrigerant. Step one is to see if the compressor is coming on at all. If it is, does it cycle off and on every few seconds? On a hot day, at idle, it should run pretty much continuously. If it doesn't come on at all, the most likely cause it that the refrigerant charge is too low and the low pressure switch on the accumulator has cut power to the compressor to save it from seizing due to lack of oil (the oil circulates with the refrigerant). The bad news is that if you are low on refrigerant you most likely have a leak. Refrigerant is not something your car consumes, like gasoline or oil; it just recirculates in what should be a perfectly sealed system. When you have a leak, refrigerant oil sometimes leaks out with the refrigerant. You have no way of knowing for sure how much. If you just keep replacing the refrigerant, like people used to do when you could buy a can of R12 for 99 cents, then eventually the compressor goes and you have to flush out the whole system and replace the compressor; plus, you still have the leak you had in the first place.

Although it's less common, the problem could be electrical. You can run a jumper wire directly from the battery to the compressor and force it to come on. If the problem is purely electrical and the system has a good charge, the accumulator will get noticeably cooler almost instantaneously. If it doesn't, disconnect the jumper immediately to avoid frying the compressor and get out your test light..

IPD sells a replacement mast for your antenna. About 17 bucks, and it takes like 3 minutes to install, once you've read the instructions. Improved my AM reception 100%.

 

Oh, good to know about the non-interference. Like he said though, a blown timing belt will wreck your day (towtruck etc). It's a task and a half, but well worth removing the worry. And with a non-interference it's less of a sensitive job. When you do it swap out the waterpump and definitely replace the thermostat and coolant. I have never bought a used car with a good thermostat haha. Change the oil, and also, have some money aside for when the relays start to go. You might even want to carry around a fuel pump relay in the car, because it will go, and when it does, it's an easy fix (unplug the old, plug in the new). If you don't have it though, it's another way to ruin a day.
Other than that, do an oil change and check all your fluids (steering brakes etc). Then just ride her around until she makes you aware of more problems haha.

 

Also, you can try to re-charge the system and have the Technician add a dye to the system. I did this on my XJ6 and could see where the dye was escaping. He only charged me an extra $20.00 for the dye.
Hope this helps

 

I use to run my B230F engine 75,000 before doing the timing belt. Congrats on your purchase.