When contacting supplier references, which questions should I ask that will elicit worthy information about the vendor?

thank you for the question but I haven't had such experience yet

1. How long you are associated with the vendor?

2. How is their response when any supply issue arises?

I believe these are the basic questions. later based on your further conversation we can squeeze thro' other questions which is relevant for the particular vendor. 

When checking supplier references, you need to collect as much information as possible to help you make a wise decision. You should interview at least three references and engage them in conversation. Verify all the information you already have about the supplier. Find out the scope of the project and how long the contract was for.

sorry for ur invitation but i'm not expert in this field

There are many aspects which require collection of information and closer examination while determining a suppliers/manufacturers qualification and eligibility to ensure successful completion of contract. These interalia may include:

Quality of material supplied and quality control regime

Timely deliveries

Litigation history

Complaint handling

Payment by the supplier to vendors of Raw Material

Involvement in corrupt practices or otherwise

For how long have you been dealing with them?

Do they match other venders prices?

What is their return and exchange policy?

What kind of guaranties have they been offering you ?

Is it good competition in the market?

Is the price fair?

Is there enough money to the buyer?

Do you prefer to buy in cash or in installments?