Belt size to bypass a/c, please?

Question

I am a single mom, trying to get my teenager back on the road. She inherited her Memaw’s 2007 Toyota Avalon and I am not able to replace the a/c compressor right now. Would anyone know what size belt i need to bypass the compressor? Thank-you so much!n

Answer 1

I don't know what size you'd need, but can show you how to figure it out for yourself. Your serpentine routing should look something like the following:

The red line is where the belt would be routed if you bypass the AC. The first thing you need to do is see if a belt which bypasses the AC would even be able to go in the space where you're are planning on routing. The easiest way to do this is to take a straight edge (like a ruler) and place it in the proposed path. If you can't put the straight edge there, the belt won't go there, so it is of no use trying.

Next, to figure out which belt you need, you need to know what you have currently. In the case of your Avalon, it can use a GATES K070822 or ACDELCO 7K822 (using these two because they are very common brands). You'll notice the part number for both is relatively the same. If you dissect them, you can see two parts to the part number. The first part, "7" is the number of ribs. The second part, "822" is the length in inches (ie: 82.2"). There are other brands which show the length in mm, which in your case would be something like "7PK2090". The belt on your car would have one or the other marking on it.

Your next task is to see what the difference is between your belt and the new routing. You need to carefully measure the distance over where the red line would traverse (where you placed your straight edge). You'll also need to measure from the same exact spots over where the current belt runs (across the AC pulley). To do this, use a heavy gauge string which will not stretch (or, a string which doesn't stretch much ... just don't stretch it while measuring). You'll want the same amount of tension during both measurements so it will be as accurate as possible. Once you have both measurements, subtract the new belt path measurement from the old belt path measurement. This will give you the amount you need to deduct from total length of your old belt to get the new belt length.

For instance, if the difference of old belt routing from the new belt routing is 7" (I'm just throwing it out there), you need to subtract that from the 82.2", which would give you 75.2". Now, you'd convert this to your new belt number, which would be K070752 for Gates or 7K752 for ACDelco. Now, this might not be the exact belt number which is available, so you have to fudge the number until you can find one which is available. In this case an ACDelco "7K752" does not exist, however, both a 7K750 and 7K755 exists. NOTE: You'll need to do some internet searching to figure out what is available. The way I found these two numbers was to input it as 7K75 without the final number after the full number (ie: 7K752) did not appear in a search.

Since this is not an exact science, what you need to do is order both of these belts (or have the parts store cross reference them to whatever brand they sell). When you have both in hand, try to install them (I'd go with the smallest one first). There will be a bit of trial and error here while you figure out which one is the right one for your vehicle. The great thing about it is, if you end up with the wrong one, you can take it back to the store ... as long as the part you're returning isn't "used", they'll gladly take the part back. By either increasing or decreasing the length of the belt you use, you can get to the right belt for your application. I agree this may be a bit arduous, but if you measure as accurately as possible and your math skills are up to snuff, it should make for minimal trips to the parts store.

When you get to the right belt, any belt you have left over can be taken back to the parts store for a full refund, so you are only out your time and the amount of gas it took you to get where you need to go. If you do plan on replacing the compressor at some point, keep your old belt so you don't have to pay for a new one at that time.

Answer 2

Welcome to the site! You don't necessarily have to bypass the compressor, it depends on what the problem is. AC compressors have an electronically activated clutch on the pulley, when the car's AC system wants to activate the compressor it will engage the clutch, which spins the compressor. If the AC clutch is seized then the compressor will always be on, if that's the problem then isolating it is one option, provided you can find a belt that works. I don't know the Avalon well enough to advise on that, as far as I know AC was standard.

If your AC clutch is working but the compressor is shot and you want to prevent the compressor from activating then you don't have to change the belt, you can deactivate the compressor instead by disabling the clutch. The AC clutch is activated using a relay (aka a solenoid switch), which should be protected by it's own fuse. Pulling the fuse or the relay should deactivate the compressor.

A quick google search shows the fuse is in the under-dashboard fuse panel, marked AC. Pull that fuse and you should be good to go, assuming that's what you need.